US 7,902,582 B2Grant
Tantalum lanthanide oxynitride films
Issue Date:2011-03-08
•25 Claims
•13 Drawing Sheets
Abstract
Electronic apparatus and methods of forming the electronic apparatus include a tantalum lanthanide oxynitride film on a substrate for use in a variety of electronic systems. The tantalum lanthanide oxynitride film may be structured as one or more monolayers. Metal electrodes may be disposed on a dielectric containing a tantalum lanthanide oxynitride film.
Metadata
Assignee
- Micron Technology, Inc.
Inventors
- Leonard Forbes
- Kie Y. Ahn
- Arup Bhattacharyya
Application Information
Application Number:US 12/470,121
Filing Date:2009-05-21
Priority Date:2006-08-31
Art Unit:2829
Classifications
IPC:
H01L21/00
Patent Drawings (13 sheets)
Description
Related Applications
[0001] This application is a divisional application of U.S. application Ser. No. 11/514,545, filed 31 Aug. 2006, now U.S. Pat. No. 7,544,604, which is incorporated herein by reference in its entirety.
[0002] This application is related to the co-pending and commonly assigned applications U.S. application Ser. No. 10/229,903, now entitled “ATOMIC LAYER DEPOSITED HfSiON DIELECTRIC FILMS WHEREIN EACH PRECURSOR IS INDEPENDENTLY PULSED,” filed on 28 Aug. 2002, now U.S. Pat. No. 7,199,023, U.S. application Ser. No. 11/216,474, entitled “LANTHANUM ALUMINUM OXYNITRIDE DIELECTRIC FILMS,” filed on 31 Aug. 2005, U.S. application Ser. No. 11/355,490, entitled “CONDUCTIVE LAYERS FOR HAFNIUM SILICON OXYNITRIDE FILMS,” filed on 16 Feb. 2006, U.S. application Ser. No. 11/010,529, now entitled “LANTHANUM HAFNIUM OXIDE DIELECTRICS,” filed on 13 Dec. 2004, now U.S. Pat. No. 7,235,501, and U.S. application Ser. No. 10/352,507, entitled “Atomic layer deposition of metal oxynitride layers as gate dielectrics and semiconductor device structures utilizing metal oxynitride layer,” filed on 27 Jan. 2003, which applications are incorporated herein by reference.
[0003] This application is also related to U.S. patent applications filed herewith on the same date. These patent applications are U.S. application Ser. No. 11/514,655, entitled “TANTALUM ALUMINUM OXYNITRIDE HIGH-K DIELECTRIC”, U.S. application Ser. No. 11/514,533, entitled “SILICON LANTHANIDE OXYNITRIDE FILMS”, U.S. application Ser. No. 11/515,143, entitled “HAFNIUM LANTHANIDE OXYNITRIDE FILMS”, U.S. application Ser. No. 11/514,601, entitled “TANTALUM SILICON OXYNITRIDE HIGH-K DIELECTRICS AND METAL GATES”, U.S. application Ser. No. 11/498,578, entitled “DEPOSITION OF ZrAlON FILMS”, U.S. application Ser. No. 11/515,114, entitled “HAFNIUM TANTALUM OXYNITRIDE HIGH-K DIELECTRIC AND METAL GATES”, and U.S. application Ser. No. 11/514,558, entitled “HAFNIUM ALUMINUM OXYNITRIDE HIGH-K DIELECTRIC AND METAL GATES”, which patent applications are incorporated herein by reference.
Technical Field
[0004] This disclosure relates generally to semiconductor devices and device fabrication.
Background
[0005] The semiconductor device industry has a market driven need to reduce the size of devices used in products such as processor chips, mobile telephones, and memory devices such as dynamic random access memories (DRAMs). Currently, the semiconductor industry relies on the ability to reduce or scale the dimensions of its basic devices. This device scaling includes scaling a dielectric layer in devices such as, for example, capacitors and silicon-based metal oxide semiconductor field effect transistors (MOSFETs), which have primarily been fabricated using silicon dioxide. A thermally grown amorphous SiO2 provides an electrically and thermodynamically stable material, where the interface of the SiO2 layer with underlying silicon provides a high quality interface as well as superior electrical isolation properties. However, increased scaling and other requirements in microelectronic devices have created the need to use other materials as dielectric regions in a variety of electronic structures.
Brief Description of the Drawings
[0006] FIG. 1 depicts an embodiment of an atomic layer deposition system for processing a tantalum lanthanide oxynitride film.
[0007] FIG. 2A shows a flow diagram of features of an embodiment for forming a tantalum lanthanide oxynitride film using atomic layer deposition and nitridization.
[0008] FIG. 2B shows a flow diagram of features of an embodiment for forming tantalum lanthanide oxide using atomic layer deposition for nitridization to a tantalum lanthanide oxynitride film.
[0009] FIG. 3 shows a flow diagram of features of an embodiment for forming a tantalum lanthanide oxynitride film using atomic layer deposition and oxidation.
[0010] FIG. 4 shows a flow diagram of features of an embodiment for forming tantalum lanthanide oxynitride film using atomic layer deposition and annealing.
[0011] FIGS. 5A-5E illustrate an embodiment of a process for forming a metal substituted electrode.
[0012] FIG. 6 illustrates a flow diagram of features of an embodiment of a metal substitution technique.
[0013] FIGS. 7A-7D illustrate an embodiment of a process for forming a self aligned conductive layer.
[0014] FIG. 8 illustrates an embodiment of a method for forming a self aligned metal gate on high-κ gate dielectrics containing a tantalum lanthanide oxynitride film.
[0015] FIG. 9 illustrates a wafer containing integrated circuits having a tantalum lanthanide oxynitride film.
[0016] FIG. 10 shows an embodiment of a transistor having a dielectric layer including a tantalum lanthanide oxynitride film.
[0017] FIG. 11 shows an embodiment of a floating gate transistor having a dielectric layer including a tantalum lanthanide oxynitride film.
[0018] FIG. 12 shows an embodiment of a capacitor having a dielectric layer including a tantalum lanthanide oxynitride film.
[0019] FIG. 13 depicts an embodiment of a dielectric layer having multiple layers including a tantalum lanthanide oxynitride layer.
[0020] FIG. 14 is a simplified diagram for an embodiment of a controller coupled to an electronic device having a dielectric layer including a tantalum lanthanide oxynitride film.
[0021] FIG. 15 illustrates a diagram for an embodiment of an electronic system including devices with a dielectric film including a tantalum lanthanide oxynitride film.
Detailed Description
[0022] The following detailed description refers to the accompanying drawings that show, by way of illustration, various embodiments of the present invention. These embodiments are described in sufficient detail to enable those skilled in the art to practice these and other embodiments. Other embodiments may be utilized, and structural, logical, and electrical changes may be made to these embodiments. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. The following detailed description is, therefore, not to be taken in a limiting sense.
[0023] In the following description, the terms wafer and substrate may be used interchangeably to refer generally to any structure on which integrated circuits are formed and also to such structures during various stages of integrated circuit fabrication. The term substrate is understood to include a semiconductor wafer. The term substrate is also used to refer to semiconductor structures during processing and may include other layers that have been fabricated thereupon. Both wafer and substrate include doped and undoped semiconductors, epitaxial semiconductor layers supported by a base semiconductor or insulator, as well as other semiconductor structures well known to one skilled in the art. The term conductor is understood to generally include n-type and p-type semiconductors and the term insulator or dielectric is defined to include any material that is less electrically conductive than the materials referred to as conductors. The following detailed description is, therefore, not to be taken in a limiting sense.
[0024] To scale a dielectric region to reduce feature sizes to provide high density electronic devices, the dielectric region should have a reduced equivalent oxide thickness (teq). The equivalent oxide thickness quantifies the electrical properties, such as capacitance, of a dielectric in terms of a representative physical thickness. teq is defined as the thickness of a theoretical SiO2 layer that would be required to have the same capacitance density as a given dielectric, ignoring leakage current and reliability considerations.
[0025] A SiO2 layer of thickness, t, deposited on a silicon surface will have a teq larger than its thickness, t. This teq results from the capacitance in the surface on which the SiO2 is deposited due to the formation of a depletion/inversion region. This depletion/inversion region can result in teq being from 3 to 6 Angstroms (Å) larger than the SiO2 thickness, t. Thus, with the semiconductor industry driving to someday scale a gate dielectric equivalent oxide thickness to less than 10 Å, the physical thickness requirement for a SiO2 layer used for a gate dielectric may need to be approximately 4 to 7 Å. Additional requirements on a SiO2 layer would depend on the electrode used in conjunction with the SiO2 dielectric. Using a conventional polysilicon electrode may result in an additional increase in teq for the SiO2 layer. Thus, designs for future devices may be directed towards a physical SiO2 dielectric layer of about 5 Å or less. Such a small thickness requirement for a SiO2 oxide layer creates additional problems.
[0026] Silicon dioxide is used as a dielectric layer in devices, in part, due to its electrical isolation properties in a SiO2—Si based structure. This electrical isolation is due to the relatively large band gap of SiO2 (8.9 eV), making it a good insulator from electrical conduction. Significant reductions in its band gap may eliminate it as a material for a dielectric region in an electronic device. As the thickness of a SiO2 layer decreases, the number of atomic layers or monolayers of the material decreases. At a certain thickness, the number of monolayers will be sufficiently small that the SiO2 layer will not have a complete arrangement of atoms as in a larger or bulk layer. As a result of incomplete formation relative to a bulk structure, a thin SiO2 layer of only one or two monolayers may not form a full band gap. The lack of a full band gap in a SiO2 dielectric may cause an effective short between an underlying electrode and an overlying electrode. This undesirable property sets a limit on the physical thickness to which a SiO2 layer can be scaled. The minimum thickness due to this monolayer effect is thought to be about 7-8 Å. Therefore, for future devices to have a teq less than about 10 Å, other dielectrics than SiO2 need to be considered for use as a dielectric region in such future devices.
[0027] In many cases, for a typical dielectric layer, the capacitance is determined as one for a parallel plate capacitance: C=κ∈0A/t, where κ is the dielectric constant, ∈0 is the permittivity of free space, A is the area of the capacitor, and t is the thickness of the dielectric. The thickness, t, of a material is related to its teq for a given capacitance, with SiO2 having a dielectric constant κox=3.9, as
t=(κ/κox)teq=(κ/3.9)teq.
Thus, materials with a dielectric constant greater than that of SiO2, 3.9, will have a physical thickness that can be considerably larger than a desired teq, while providing the desired equivalent oxide thickness. For example, an alternative dielectric material with a dielectric constant of 10 could have a thickness of about 25.6 Å to provide a teq of 10 Å, not including any depletion/inversion layer effects. Thus, a reduced equivalent oxide thickness for transistors can be realized by using dielectric materials with higher dielectric constants than SiO2.
t=(κ/κox)teq=(κ/3.9)teq.
Thus, materials with a dielectric constant greater than that of SiO2, 3.9, will have a physical thickness that can be considerably larger than a desired teq, while providing the desired equivalent oxide thickness. For example, an alternative dielectric material with a dielectric constant of 10 could have a thickness of about 25.6 Å to provide a teq of 10 Å, not including any depletion/inversion layer effects. Thus, a reduced equivalent oxide thickness for transistors can be realized by using dielectric materials with higher dielectric constants than SiO2.
[0028] The thinner equivalent oxide thickness required for lower device operating voltages and smaller device dimensions may be realized by a significant number of materials, but additional fabricating requirements make determining a suitable replacement for SiO2 difficult. The current view for the microelectronics industry is still for silicon-based devices. This may require that the dielectric material employed be grown on a silicon substrate or a silicon layer, which places significant constraints on the substitute dielectric material. During the formation of the dielectric on the silicon layer, there exists the possibility that a small layer of SiO2 could be formed in addition to the desired dielectric. The result would effectively be a dielectric layer consisting of two sublayers in parallel with each other and the silicon layer on which the dielectric is formed. In such a case, the resulting capacitance would be that of two dielectrics in series. As a result, the teq of the dielectric layer would be the sum of the SiO2 thickness and a multiplicative factor of the thickness, t, of the dielectric being formed, written as
teq=tSiO2 +(κox/κ)t.
Thus, if a SiO2 layer is formed in the process, the teq is again limited by a SiO2 layer. In the event that a barrier layer is formed between the silicon layer and the desired dielectric in which the barrier layer prevents the formation of a SiO2 layer, the teq would be limited by the layer with the lowest dielectric constant. However, whether a single dielectric layer with a high dielectric constant or a barrier layer with a higher dielectric constant than SiO2 is employed, the layer interfacing with the silicon layer should provide a high quality interface.
teq=tSiO
Thus, if a SiO2 layer is formed in the process, the teq is again limited by a SiO2 layer. In the event that a barrier layer is formed between the silicon layer and the desired dielectric in which the barrier layer prevents the formation of a SiO2 layer, the teq would be limited by the layer with the lowest dielectric constant. However, whether a single dielectric layer with a high dielectric constant or a barrier layer with a higher dielectric constant than SiO2 is employed, the layer interfacing with the silicon layer should provide a high quality interface.
[0029] Using SiO2 as a dielectric layer in a device has allowed the formation of a SiO2 layer that results in an amorphous dielectric. Having an amorphous structure for a dielectric provides for reducing problems of leakage current associated with grain boundaries in polycrystalline dielectrics that provide high leakage paths. Additionally, grain size and orientation changes throughout a polycrystalline dielectric can cause variations in the film's dielectric constant, along with uniformity and surface topography problems. Materials having a high dielectric constant relative to SiO2 may also have a crystalline form, at least in a bulk configuration. The best candidates for replacing SiO2 as a dielectric in a device are those that can be fabricated as a thin layer with an amorphous form and that have high dielectric constants.
[0030] Capacitor applications have used high-κ dielectric materials, which are insulating materials having a dielectric constant greater than silicon dioxide. Such high-κ dielectric materials include silicon oxynitride (SiON, κ˜6), alumina (Al2O3, κ˜9), and oxide/nitride composites (SiO2/Si3N4, κ˜6). Other possible candidates include metal oxides (κ˜8-80), nitrides (κ˜7-30), oxynitrides (κ˜6-25), silicates (κ˜6-20), carbides (κ˜6-15), and complex titanates (κ˜>100). Factors for selecting appropriate materials include physical, chemical and thermal stability as well as etch-ability and stoichiometric reproducibility. In field effect transistor (FET) applications, there are other factors to consider while addressing device scalability. The selected dielectric should provide stable amorphous and adherent films in the thickness range of 1 nm to 100 nm at temperatures ranging from room temperature to 1000° C. A relatively defect-free composition that is uniform and reproducible with a fixed charge density and trap density of less than 1011 cm−2 in films of such composition is a factor. A factor includes dielectric materials that provide a stable non-reactive interface with a silicon substrate such that the interface has an interface state density much less than 1011 cm−2. Such interface state densities may occur when silicon bonds at the interface are saturated with high strength covalent bonds with molecular elements of the dielectric material. Another factor deals with current transport through the dielectric that should be controlled by tunneling, which is independent of temperature, rather than by trap-assisted thermally dependent transport. The conductivity of the dielectric should be equal to or lower than SiO2 films when voltage is stressed to a field strength of 5×106 V/cm. To address the current transport, a dielectric material having a bandgap greater than 5 eV and having an electron and hole barrier height greater than 2 eV at a silicon interface may be considered. An additional factor to consider is using dielectric materials with a destructive breakdown strength greater than 6×106 V/cm. Other factors for selecting a dielectric material for use in a variety of electronic devices, such as for the dielectric in FETs, relates to processing characteristics. Such processing characteristics include compatibility with gate material, selective etch-ability, chemical inertness to contaminants, dopant and post processing environments (temperature, pressure, ambients), and intrinsic properties associated with annealing of defects/damages caused by post-processing such as ion-implantation, plasma-radiation, and gate/back-end processing.
[0031] In various embodiments, mixed metal oxynitrides (with silicon included as a metal) are constructed as dielectric films in a variety of electronic devices and systems. Most oxynitrides are thermally stable and can integrate into semiconductor device processing. With nitrogen concentration in an oxynitride film at 30% or higher, such oxynitrides are chemically inert. With processing conditions controlled to provide appropriately low partial pressures of hydrogen and ON ions, oxynitride films with a wide range of nitrogen to oxygen ratio can be deposited over a silicon substrate with low fixed charge and interface states density. On the other hand, charge trapping and transport characteristics are dependent on relative ratio of nitrogen to oxygen content in the constructed film. Films with nitrogen concentration twice that of oxygen (for example, approximately 40 atomic percent nitrogen, approximately 20 atomic percent oxygen, and approximately 40 atomic percent metal or silicon) have a lower bandgap, higher trap density, and transport characteristics dominated by Frenkel-Poole conduction. Such materials may not be well suited for gate dielectric applications. However, such films exhibit higher κ values. With increasing oxygen concentration in oxynitride films, the bandgap is raised, current leakage is reduced, and the low frequency κ value is also somewhat reduced. In addition with increasing oxygen concentration, the trap density is reduced, the trap energy depth is increased, and the carrier transport ceases to be trap-assisted, exhibits tunneling conduction, and has a weak temperature dependence, if any. In various embodiments, a dielectric layer includes an oxynitride film having approximately 30 atomic % oxygen and approximately 30-35 atomic % nitrogen. With high enough nitrogen content, oxygen-vacancy induced defects in films is negligible when compared with metal oxides.
[0032] Silicon oxynitride (SiON) has been used as a gate dielectric and gate insulator for a non-volatile FET device. Silicon oxynitride at a composition range of Si2ON2 exhibits a dielectric constant of 6.5 and a bandgap of approximately 6.5 eV compared to a stoichiometric nitride of κ=7.5 and a bandgap of 5.1 eV. Aluminum oxynitride (AlON) is expected to have a bandgap greater than 5 eV with a κ value similar to SiON. Compared to SiON, metal oxynitrides such as ZrON, HfON, LaON, and TaON and other single metal oxynitrides are expected to have a lower bandgap.
[0033] In various embodiments, bimetal (or metal/silicon) oxynitrides based on Si, Al, Hf, La, and Ta are used as dielectric films in a variety of electronic devices and systems. These bimetal oxynitrides may provide a bandgap range from 5 eV to greater than 7 eV. Estimates for bandgaps include a bandgap of Si—Al—ON of greater than 7 eV, a bandgap of Si—Hf—ON of about 6.9 eV, a bandgap of Al—Hf—ON of about 6.8 eV, a bandgap of Si—Ta—ON of about 6 eV, a bandgap of Al—Ta—ON of about 6 eV. Bimetal oxynitrides Hf—Ta—ON, Hf—La—ON, Al—La—ON, Ta—La—ON, and Si—La—ON are estimated to exhibit significantly lower bandgaps. The K value for Si—Al—ON is estimated at approximately 7 to 8, while the K values for the other oxynitrides of this group are estimated to be in the range from about 15 to 25.
[0034] In an embodiment, a film of tantalum lanthanide oxynitride may be used as a dielectric layer for application in a variety of electronic devices, replacing the use of silicon oxide to provide a higher dielectric constant. The tantalum lanthanide oxynitride film may be formed as a tantalum lanthanum oxynitride film. In other embodiments, one of more lanthanides may be used to form a tantalum lanthanide oxynitride film. The lanthanide, represented by the expression Ln, may include one or more elements from the lanthanide group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). In various embodiments, a dielectric layer may be constructed containing tantalum lanthanide oxynitride formed using atomic layer deposition with a metal electrode formed in contact with the dielectric layer. The metal electrode may be formed by atomic layer deposition. The metal electrode may be formed by substituting a desired metal material for a previously disposed substitutable material. The metal electrode may be formed as a self aligned metal electrode on and contacting the dielectric layer. The metal electrode may be formed on the dielectric layer using a previously disposed sacrificial carbon layer on the dielectric layer and sacrificial carbon sidewall spacers adjacent to the sacrificial carbon layer.
[0035] The term tantalum lanthanide oxynitride is used herein with respect to a composition that essentially consists of tantalum, lanthanide, oxygen, and nitrogen in a form that may be stoichiometric, non-stoichiometric, or a combination of stoichiometric and non-stoichiometric. In an embodiment, the lanthanide may be lanthanum. Alternatively, the lanthanide may be one or more elements from the lanthanide group of elements. A tantalum lanthanide oxynitride film may also be referred to as a tantalum lanthanide oxygen nitrogen film. Other nomenclature for a composition that essentially consists of tantalum, lanthanide, oxygen, and nitrogen may be known to those skilled in the art. In an embodiment, tantalum lanthanide oxynitride may be formed substantially as a stoichiometric tantalum lanthanide oxynitride film. In an embodiment, tantalum lanthanide oxynitride may be formed substantially as a non-stoichiometric tantalum lanthanide oxynitride film. In an embodiment, tantalum lanthanide oxynitride may be formed substantially as a combination film of non-stoichiometric tantalum lanthanide oxynitride and stoichiometric tantalum lanthanide oxynitride. Herein, a tantalum lanthanide oxynitride composition may be expressed as TaLnON, TaLnONx, TaxLnyOzNr, or other equivalent form. Herein, a tantalum lanthanum oxynitride composition may be expressed as TaLaON, TaLaONr, TaxLayOzNr, or other equivalent form. The expression TaLnON or its equivalent forms may be used to include TaLnON in a form that is stoichiometric, non-stoichiometric, or a combination of stoichiometric and non-stoichiometric tantalum lanthanide oxynitride. The expressions LnO, LnOz, or its equivalent forms may be used to include lanthanide oxide in a form that is stoichiometric, non-stoichiometric, or a combination of stoichiometric and non-stoichiometric. With respect to forms that are stoichiometric, non-stoichiometric, or a combination of stoichiometric and non-stoichiometric, expressions such as LnN, LaO, LaN, TaON, LnON, LaON, LaOz, LaNr, TaOt, TaNs, TaONr, LnONr, LaONr etc. may be used in a similar manner as LnOz. In various embodiments, a tantalum lanthanide oxynitride film may be doped with elements or compounds other than tantalum, lanthanide, oxygen, and nitrogen.
[0036] In an embodiment, a tantalum lanthanide oxynitride dielectric film may be formed using atomic layer deposition (ALD). Forming such structures using atomic layer deposition may allow control of transitions between material layers. As a result of such control, atomic layer deposited tantalum lanthanide oxynitride dielectric films can have an engineered transition with a surface on which it is formed.
[0037] ALD, also known as atomic layer epitaxy (ALE), is a modification of chemical vapor deposition (CVD) and is also called “alternatively pulsed-CVD.” In ALD, gaseous precursors are introduced one at a time to the substrate surface mounted within a reaction chamber (or reactor). This introduction of the gaseous precursors takes the form of pulses of each gaseous precursor. In a pulse of a precursor gas, the precursor gas is made to flow into a specific area or region for a short period of time. Between the pulses, the reaction chamber may be purged with a gas, where the purging gas may be an inert gas. Between the pulses, the reaction chamber may be evacuated. Between the pulses, the reaction chamber may be purged with a gas and evacuated.
[0038] In a chemisorption-saturated ALD (CS-ALD) process, during the first pulsing phase, reaction with the substrate occurs with the precursor saturatively chemisorbed at the substrate surface. Subsequent pulsing with a purging gas removes precursor excess from the reaction chamber.
[0039] The second pulsing phase introduces another precursor on the substrate where the growth reaction of the desired film takes place. Subsequent to the film growth reaction, reaction byproducts and precursor excess are purged from the reaction chamber. With favorable precursor chemistry where the precursors absorb and react with each other aggressively on the substrate, one ALD cycle can be performed in less than one second in properly designed flow type reaction chambers. Typically, precursor pulse times range from about 0.5 sec to about 2 to 3 seconds. Pulse times for purging gases may be significantly longer, for example, pulse times of about 5 to about 30 seconds.
[0040] In ALD, the saturation of all the reaction and purging phases makes the growth self-limiting. This self-limiting growth results in large area uniformity and conformality, which has important applications for such cases as planar substrates, deep trenches, and in the processing of porous silicon and high surface area silica and alumina powders. Atomic layer deposition provides control of film thickness in a straightforward manner by controlling the number of growth cycles.
[0041] The precursors used in an ALD process may be gaseous, liquid or solid. However, liquid or solid precursors should be volatile. The vapor pressure should be high enough for effective mass transportation. Also, solid and some liquid precursors may need to be heated inside the atomic layer deposition system and introduced through heated tubes to the substrates. The necessary vapor pressure should be reached at a temperature below the substrate temperature to avoid the condensation of the precursors on the substrate. Due to the self-limiting growth mechanisms of ALD, relatively low vapor pressure solid precursors can be used, though evaporation rates may vary somewhat during the process because of changes in their surface area.
[0042] There are several other characteristics for precursors used in ALD. The precursors should be thermally stable at the substrate temperature, because their decomposition may destroy the surface control of the ALD method that relies on the reaction of the precursor at the substrate surface. A slight decomposition, if slow compared to the ALD growth, may be tolerated.
[0043] The precursors should chemisorb on or react with the surface, though the interaction between the precursor and the surface as well as the mechanism for the adsorption is different for different precursors. The molecules at the substrate surface should react aggressively with the second precursor to form the desired solid film. Additionally, precursors should not react with the film to cause etching, and precursors should not dissolve in the film. Using highly reactive precursors in ALD contrasts with the selection of precursors for conventional CVD.
[0044] The by-products in the reaction should be gaseous in order to allow their easy removal from the reaction chamber. Further, the by-products should not react or adsorb on the surface.
[0045] In a reaction sequence ALD (RS-ALD) process, the self-limiting process sequence involves sequential surface chemical reactions. RS-ALD relies on chemistry between a reactive surface and a reactive molecular precursor. In an RS-ALD process, molecular precursors are pulsed into the ALD reaction chamber separately. A metal precursor reaction at the substrate may be followed by an inert gas pulse to remove excess precursor and by-products from the reaction chamber prior to pulsing the next precursor of the fabrication sequence.
[0046] By RS-ALD, films can be layered in equal metered sequences that may all be identical in chemical kinetics, deposition per cycle, composition, and thickness. RS-ALD sequences generally deposit less than a full layer per cycle. Typically, a deposition or growth rate of about 0.25 to about 2.00 Å per RS-ALD cycle may be realized.
[0047] Processing by RS-ALD provides continuity at an interface avoiding poorly defined nucleating regions that are typical for chemical vapor deposition (<20 Å) and physical vapor deposition (<50 Å), conformality over a variety of substrate topologies due to its layer-by-layer deposition technique, use of low temperature and mildly oxidizing processes, lack of dependence on the reaction chamber, growth thickness dependent solely on the number of cycles performed, and ability to engineer multilayer laminate films with a resolution of one to two monolayers. RS-ALD processes allow for deposition control on the order of monolayers and the ability to deposit monolayers of amorphous films.
[0048] Herein, a sequence refers to the ALD material formation based on an ALD reaction of a precursor with its reactant precursor. For example, forming tantalum nitride from a TaCl5 precursor and NH3, as its reactant precursor, includes a tantalum/nitrogen sequence. In various ALD processes that form a nitride or a composition that contains nitrogen, a reactant precursor that contains nitrogen is used to supply nitrogen. Herein, a precursor that contains nitrogen and that supplies nitrogen to be incorporated in the ALD composition formed, which may be used in an ALD process with precursors supplying the other elements in the ALD composition, is referred to as a nitrogen reactant precursor. In the above example, NH3 is a nitrogen reactant precursor. Similarly, an ALD sequence for a metal oxide may be referenced with respect to the metal and oxygen. For example, an ALD sequence for tantalum oxide may also be referred to as a tantalum/oxygen sequence. In various ALD processes that form an oxide or a composition that contains oxygen, a reactant precursor that contains oxygen is used to supply the oxygen. Herein, a precursor that contains oxygen and that supplies oxygen to be incorporated in the ALD composition formed, which may be used in an ALD process with precursors supplying the other elements in the ALD composition, is referred to as an oxygen reactant precursor. With an ALD process using TaCl5 and water vapor to form tantalum oxide, water vapor is an oxygen reactant precursor. An ALD cycle may include pulsing a precursor, pulsing a purging gas for the precursor, pulsing a reactant precursor, and pulsing the reactant precursor's purging gas. An ALD cycle may include pulsing a precursor, evacuating the reactant chamber, pulsing a reactant precursor, and evacuating the reactant chamber. An ALD cycle may include pulsing a precursor, pulsing a purging gas for the precursor and evacuating the reactant chamber, pulsing a reactant precursor, and pulsing the reactant precursor's purging gas and evacuating the reactant chamber.
[0049] In forming a layer of a metal species, an ALD sequence may deal with pulsing a reactant precursor to the substrate surface on which a metal-containing species has been absorbed such that the reactant precursor reacts with the metal-containing species resulting in the deposited metal and a gaseous by-product that can be removed during the subsequent purging/evacuating process. Alternatively, in forming a layer of a metal species, an ALD sequence may deal with reacting a precursor containing the metal species with a substrate surface. A cycle for such a metal forming sequence may include pulsing a purging gas after pulsing the precursor containing the metal species to deposit the metal. Additionally, deposition of a semiconductor material may be realized in a manner similar to forming a layer of a metal, given the appropriate precursors for the semiconductor material.
[0050] In an ALD formation of a composition having more than two elements, a cycle may include a number of sequences to provide the elements of the composition. For example, a cycle for an ALD formation of an ABOx composition may include sequentially pulsing a first precursor/a purging gas for the first precursor/a first reactant precursor/the first reactant precursor's purging gas/a second precursor/a purging gas for the second precursor/a second reactant precursor/the second reactant precursor's purging gas, which may be viewed as a cycle having two sequences. In an embodiment, a cycle may include a number of sequences for element A and a different number of sequences for element B. There may be cases in which ALD formation of an ABOx composition uses one precursor that contains the elements A and B, such that pulsing the AB containing precursor followed by its reactant precursor onto a substrate may include a reaction that forms ABOx on the substrate to provide an AB/oxygen sequence. A cycle of an AB/oxygen sequence may include pulsing a precursor containing A and B, pulsing a purging gas for the precursor, pulsing an oxygen reactant precursor to the A/B precursor, and pulsing a purging gas for the reactant precursor. A cycle may be repeated a number of times to provide a desired thickness of the composition. In an embodiment, a cycle for an ALD formation of the quaternary composition, tantalum lanthanide oxygen nitrogen, may include sequentially pulsing a first precursor/a purging gas for the first precursor/a first reactant precursor/the first reactant precursor's purging gas/a second precursor/a purging gas for the second precursor/a second reactant precursor/the second reactant precursor's purging gas/a third precursor/a purging gas for the third precursor/a third reactant precursor/the third reactant precursor's purging gas, which may be viewed as a cycle having three sequences. In an embodiment, a layer substantially of a tantalum lanthanide oxynitride composition is formed on a substrate mounted in a reaction chamber using ALD in repetitive lanthanide/oxygen and tantalum/nitrogen sequences using precursor gases individually pulsed into the reaction chamber. In an embodiment, a layer substantially of a tantalum lanthanide oxynitride composition is formed on a substrate mounted in a reaction chamber using ALD in repetitive lanthanide/nitrogen and tantalum/oxygen sequences using precursor gases individually pulsed into the reaction chamber. In an embodiment, a substantially tantalum lanthanide oxynitride composition is formed by ALD having approximately 30% nitrogen and 30% oxygen concentrations in the resultant TaLnON dielectric film.
[0051] FIG. 1 shows an embodiment of an atomic layer deposition system 100 for processing a dielectric film containing a TaxLnyOzNr layer. The elements depicted are those elements necessary for discussion of various embodiments for forming TaLnON such that those skilled in the art may practice embodiments of the present invention without undue experimentation. A substrate 110 is located inside a reaction chamber 120 of ALD system 100. Also located within reaction chamber 120 is a heating element 130, which is thermally coupled to substrate 110 to control the substrate temperature. A gas-distribution fixture 140 introduces precursor gases to the substrate 110. Each precursor gas originates from individual gas sources 150-155 whose flow is controlled by mass-flow controllers 156-161, respectively. Gas sources 150-155 provide a precursor gas either by storing the precursor as a gas or by providing a location and apparatus for evaporating a solid or liquid material to form the selected precursor gas. Furthermore, additional gas sources may be included, one for each metal precursor employed and one for each reactant precursor associated with each metal precursor.
[0052] Also included in the ALD system are purging gas sources 163, 164, each of which is coupled to mass-flow controllers 166, 167, respectively. Furthermore, additional purging gas sources may be constructed in ALD system 100, one purging gas source for each precursor gas. For a process that uses the same purging gas for multiple precursor gases, less purging gas sources are required for ALD system 100. Gas sources 150-155 and purging gas sources 163-164 are coupled by their associated mass-flow controllers to a common gas line or conduit 170, which is coupled to the gas-distribution fixture 140 inside reaction chamber 120. Gas conduit 170 is also coupled to vacuum pump, or exhaust pump, 181 by mass-flow controller 186 to remove excess precursor gases, purging gases, and by-product gases at the end of a purging sequence from gas conduit 170.
[0053] Vacuum pump, or exhaust pump, 182 is coupled by mass-flow controller 187 to remove excess precursor gases, purging gases, and by-product gases at the end of a purging sequence from reaction chamber 120. For convenience, control displays, mounting apparatus, temperature sensing devices, substrate maneuvering apparatus, and necessary electrical connections as are known to those skilled in the art are not shown in FIG. 1 . The use, construction and fundamental operation of reaction chambers for deposition of films are understood by those of ordinary skill in the art of semiconductor fabrication. Embodiments of the present invention may be practiced on a variety of such reaction chambers without undue experimentation. Furthermore, one of ordinary skill in the art will comprehend the necessary detection, measurement, and control techniques in the art of semiconductor fabrication upon reading the disclosure.
[0054] In an embodiment, a tantalum lanthanide oxynitride layer may be structured as one or more monolayers. A film of tantalum lanthanide oxynitride, structured as one or more monolayers, may have a thickness that ranges from a monolayer to thousands of angstroms or more. The film may be processed using atomic layer deposition. Embodiments of an atomic layer deposited tantalum lanthanide oxynitride layer have a larger dielectric constant than silicon dioxide. Such dielectric layers provide a significantly thinner equivalent oxide thickness compared with a silicon oxide layer having the same physical thickness. Alternatively, such dielectric layers provide a significantly thicker physical thickness than a silicon oxide layer having the same equivalent oxide thickness. This increased physical thickness aids in reducing leakage current.
[0055] Prior to forming the tantalum lanthanide oxynitride film using ALD, the surface on which the tantalum lanthanide oxynitride film is to be deposited may undergo a preparation stage. The surface may be the surface of a substrate for an integrated circuit. In an embodiment, the substrate used for forming a transistor may include a silicon or silicon containing material. In other embodiments, silicon germanium, germanium, gallium arsenide, silicon-on-sapphire substrates, or other suitable substrates may be used. A preparation process may include cleaning the substrate and forming layers and regions of the substrate, such as drains and sources, prior to forming a gate dielectric in the formation of a metal insulator semiconductor (MIS) transistor. Alternatively, active regions may be formed after forming the dielectric layer, depending on the over-all fabrication process implemented. In an embodiment, the substrate is cleaned to provide an initial substrate depleted of its native oxide. In an embodiment, the initial substrate is cleaned also to provide a hydrogen-terminated surface. In an embodiment, a silicon substrate undergoes a final hydrofluoric (HF) rinse prior to ALD processing to provide the silicon substrate with a hydrogen-terminated surface without a native silicon oxide layer.
[0056] Cleaning immediately preceding atomic layer deposition aids in reducing an occurrence of silicon oxide as an interface between a silicon-based substrate and a tantalum lanthanide oxynitride dielectric formed using the atomic layer deposition process. The material composition of an interface layer and its properties are typically dependent on process conditions and the condition of the substrate before forming the dielectric layer. Though the existence of an interface layer may effectively reduce the dielectric constant associated with the dielectric layer and its substrate interface layer, a SiO2 interface layer or other composition interface layer may improve the interface density, fixed charge density, and channel mobility of a device having this interface layer.
[0057] The sequencing of the formation of the regions of an electronic device, such as a transistor, being processed may follow typical sequencing that is generally performed in the fabrication of such devices as is well known to those skilled in the art. Included in the processing prior to forming a dielectric may be the masking of substrate regions to be protected during the dielectric formation, as is typically performed in semiconductor fabrication. In an embodiment, an unmasked region includes a body region of a transistor; however, one skilled in the art will recognize that other semiconductor device structures may utilize this process.
[0058] In various embodiments, between each pulsing of a precursor used in an atomic layer deposition process, a purging gas may be pulsed into the ALD reaction chamber. Between each pulsing of a precursor, the ALD reactor chamber may be evacuated using vacuum techniques as is known by those skilled in the art. Between each pulsing of a precursor, a purging gas may be pulsed into the ALD reaction chamber and the ALD reactor chamber may be evacuated.
[0059] In an embodiment, an ALD cycle for forming TaLnON includes sequencing component-containing precursors in the order of lanthanide, oxygen, tantalum, and nitrogen with appropriate purging between the different component-containing precursors. Full coverage or partial coverage of a monolayer on a substrate surface may be attained for pulsing of a metal-containing precursor. In an embodiment, an ALD cycle for forming TaLnON includes sequencing the component-containing precursors in various permutations. In an embodiment, an ALD cycle to form tantalum lanthanide oxynitride includes a number, x, of lanthanide/oxygen sequences and a number, y, of tantalum/nitrogen sequences. In an embodiment, an ALD cycle to form tantalum lanthanide oxynitride includes a number, x, of lanthanide/nitrogen sequences and a number, y, of tantalum/oxygen sequences. In an embodiment, the number of sequences x and y is selected to engineer the relative amounts of tantalum, lanthanide, oxygen, and nitrogen. In an embodiment, the number of sequences x and y is selected to form a nitrogen-rich tantalum lanthanide oxynitride. In an embodiment, the number of sequences x and y are selected to form an oxygen-rich tantalum lanthanide oxynitride. The tantalum lanthanide oxynitride may be engineered as a lanthanide-rich dielectric relative to the amount of tantalum in the dielectric. The tantalum lanthanide oxynitride may be engineered as a tantalum-rich dielectric relative to the amount of lanthanide in the dielectric. The pulsing of the individual component-containing precursors may be performed independently in a non-overlapping manner using the individual gas sources 150-155 and flow controllers 156-161 of ALD system 100 of FIG. 1 .
[0060] Each precursor may be pulsed into the reaction chamber for a predetermined period, where the predetermined period can be set separately for each precursor. Additionally, for various ALD formations, each precursor may be pulsed into the reaction chamber under separate environmental conditions. The substrate may be maintained at a selected temperature and the reaction chamber maintained at a selected pressure independently for pulsing each precursor. Appropriate temperatures and pressures may be maintained, whether the precursor is a single precursor or a mixture of precursors.
[0061] A number of precursors containing a lanthanide may be used to provide the lanthanide to a substrate for an integrated circuit. In an embodiment, a precursor containing a lanthanide may include Ln(thd)3 (thd=2,2,6,6-tetramethyl-3,5-heptanedione)=Ln(C11H19O2)3. In an embodiment, a lanthanum-containing precursor is pulsed onto a substrate in an ALD reaction chamber. A number of precursors containing lanthanum that may be used includes, but is not limited to, La(thd)3, La(N(SiMe3)2)3═C18H54N3LaSi6, tris (2,2,6,6-tetramethyl-3,5-heptanedionato)lanthanum (III) tetraglyme adduct=La(C11H19O2)3CH3(OCH2CH2)4OCH3, trisethylcyclopentadionatolanthanum (La(EtCp)3), and trisdipyvaloylmethanatolanthanum (La(DPM)3). Me is an abbreviation for CH3, Et is an abbreviation for ethyl (CH2CH3), and Cp is an abbreviation for a cyclopentadienyl ligand having the formula C5H5. In an embodiment, H2 may be pulsed along with a La(EtCp)3 precursor or a La(DPM)3 precursor to reduce carbon contamination in the fabricated film. Other precursors may be used in embodiments in which the lanthanide is other than lanthanum.
[0062] In various embodiments, after pulsing the lanthanide-containing precursor and purging the reaction chamber of excess precursor and by-products from pulsing the precursor, a reactant precursor may be pulsed into the reaction chamber. The reactant precursor may be an oxygen reactant precursor, for a lanthanum/oxygen sequence, that may include, but is not limited to, one or more of water, atomic oxygen, molecular oxygen, ozone, hydrogen peroxide, a water-hydrogen peroxide mixture, alcohol, or nitrous oxide. The reactant precursor may be a nitrogen reactant precursor, for a lanthanum/nitrogen sequence, that may include, but is not limited to, nitrogen, ammonia (NH3), tert-butylamine (C4H11N), allylamine (C3H7N), 1,1-dimethylhydrazine ((CH3)2NNH2). In addition, the pulsing of the lanthanide precursor may use a pulsing period that provides uniform coverage of a monolayer on the surface or may use a pulsing period that provides partial coverage of a monolayer on the surface during a lanthanide sequence.
[0063] A number of precursors containing tantalum may be used to provide the tantalum to a substrate for an integrated circuit. Precursors containing tantalum may include, but are not limited to, tantalum ethoxide [Ta(OC2H5)5] and tantalum halides, such as TaCl5, TaBr5, and TaF5. In various embodiments, after pulsing the lanthanide-containing precursor and purging the reaction chamber of excess precursor and by-products from pulsing the precursor, a reactant precursor may be pulsed into the reaction chamber. The reactant precursor may be an nitrogen reactant precursor, for a tantalum/nitrogen sequence, that may include, but is not limited to, one or more of nitrogen, ammonia (NH3), tert-butylamine (C4H11N), allylamine (C3H7N), 1,1-dimethylhydrazine ((CH3)2NNH2). The reactant precursor may be an oxygen reactant precursor, for a tantalum/oxygen sequence, that may include, but is not limited to, one or more of water, atomic oxygen, molecular oxygen, ozone, hydrogen peroxide, a water-hydrogen peroxide mixture, alcohol, or nitrous oxide. In addition, the pulsing of the tantalum precursor may use a pulsing period that provides uniform coverage of a monolayer on the surface or may use a pulsing period that provides partial coverage of a monolayer on the surface during a tantalum sequence.
[0064] In various embodiments, nitrogen may be used as a purging gas and a carrier gas for one or more of the sequences used in the ALD formation of tantalum lanthanide oxynitride. Alternatively, hydrogen, argon gas, or other inert gases may be used as the purging gas. Excess precursor gas and reaction by-products may be removed by the purge gas. Excess precursor gas and reaction by-products may be removed by evacuation of the reaction chamber using various vacuum techniques. Excess precursor gas and reaction by-products may be removed by the purge gas and by evacuation of the reaction chamber.
[0065] In an embodiment, after repeating a selected number of ALD cycles, a determination is made as to whether the number of cycles equals a predetermined number to form the desired tantalum lanthanide oxynitride layer. If the total number of cycles to form the desired thickness has not been completed, a number of cycles is repeated. In an embodiment, the thickness of a tantalum lanthanide oxynitride layer formed by atomic layer deposition is determined by a fixed growth rate for the pulsing periods and precursors used, set at a value such as N nm/cycle, and the number of cycles conducted. In an embodiment, depending on the precursors used for ALD formation of a TaLnON film, the process is conducted in an ALD window, which is a range of temperatures in which the growth rate is substantially constant. In an embodiment, if such an ALD window is not available, the ALD process is conducted at the same set of temperatures for each ALD sequence in the process. For a desired tantalum lanthanide oxynitride layer thickness, t, in an application, the ALD process is repeated for t/N total cycles. Once the t/N cycles have completed, no further ALD processing for the tantalum lanthanide oxynitride layer is required. In an embodiment, a tantalum lanthanide oxynitride layer processed at relatively low temperatures associated with atomic layer deposition provides an amorphous layer.
[0066] In an embodiment, a TaLnON film may be grown to a desired thickness by repetition of a process including atomic layer deposition of layers of LnO and TaN and/or layers of TaO and LnN followed by annealing. In an embodiment, a base thickness may be formed according to various embodiments such that forming a predetermined thickness of a TaLnON film may be conducted by forming a number of layers having the base thickness. As can be understood by one skilled in the art, determining the base thickness depends on the application and can be determined during initial processing without undue experimentation. Relative amounts of tantalum, lanthanide, oxygen, and nitrogen in a TaLnON film may be controlled by regulating the relative thicknesses of the individual layers of oxides and nitrides formed. In addition, relative amounts of tantalum, lanthanide, oxygen, and nitrogen in a TaLnON film may be controlled by forming a layer of TaLnON as multiple layers of different base thickness and by regulating the relative thicknesses of the individual layers of oxides and nitrides formed in each base layer prior to annealing. As can be understood by those skilled in the art, particular effective growth rates for the engineered tantalum lanthanide oxynitride film can be determined during normal initial testing of the ALD system used in processing a tantalum lanthanide oxynitride dielectric for a given application without undue experimentation.
[0067] FIG. 2A shows a flow diagram of features of an embodiment for forming TaLnON using atomic layer deposition and nitridization. At 210, a layer of TaLnO is formed using atomic layer deposition. At 220, the layer of TaLnO is subjected to a nitridization to form a TaLnON film. The nitridization may be a high temperature nitridization. In the nitridization process, active nitrogen may be introduced by microwave plasma. In the nitridization process, active nitrogen may be introduced by a NH3 anneal. A high temperature nitridization is a nitridizing process that is performed at temperatures equal to or above 500° C. In various embodiments, TaLnO may be formed by atomic layer deposition using ALD cycles of lanthanide/oxygen sequences and tantalum/oxygen sequences. Depending on the amounts of lanthanide, tantalum, and oxygen to be provided in the TaLaO film, the ALD cycle can be selected from a number of different permutations of lanthanide/oxygen sequences and tantalum/oxygen sequences.
[0068] FIG. 2B shows a flow diagram of features of an embodiment for forming TaLnO using atomic layer deposition for nitridization to a TaLnON film. At 230, a layer of lanthanide oxide is formed on a substrate by atomic layer deposition. At 240, a layer of tantalum oxide is formed by atomic layer deposition on the layer of lanthanide oxide. At 250, the layers of lanthanide oxide and tantalum oxide are annealed to form a layer of TaLnO. The order of forming LnO and TaO may be interchanged. The layer of TaLnO may be nitridized to form TaLnON. Alternatively, the layers of lanthanide oxide and tantalum oxide may be nitridized during the annealing process. In an embodiment, alternating layers of ALD lanthanide oxide and ALD tantalum oxide may be formed to a desired thickness prior to nitridization. In an embodiment, a layer of ALD lanthanide oxide and a layer of ALD tantalum oxide may be formed, each to a desired thickness, the layers of ALD lanthanide oxide and ALD tantalum oxide nitridized to form a TaLnON layer. Then, a layer of ALD lanthanide oxide and a layer of ALD tantalum oxide may be formed on the TaLnON layer, the layers of ALD lanthanide oxide and ALD tantalum oxide nitridized to form a TaLnON layer on and contiguous with the previously formed TaLnON layer. This process may be continued until the desired thickness of TaLnON is formed.
[0069] In an embodiment, ALD LaO may be formed using a number of precursors containing lanthanum to provide the lanthanum to a substrate for an integrated circuit. Such lanthanum-containing precursors include, but are not limited to, La(thd)3, tris (2,2,6,6-tetramethyl-3,5-heptanedionato)lanthanum (III) tetraglyme adduct, La(EtCp)3, and La(DPM)3. After pulsing the lanthanum-containing precursor and purging the reaction chamber of excess precursor and by-products from pulsing the precursor, an oxygen reactant precursor may be pulsed into the reaction chamber. The oxygen reactant precursor may include, but is not limited to, one or more of water, atomic oxygen, molecular oxygen, ozone, hydrogen peroxide, a water-hydrogen peroxide mixture, alcohol, or nitrous oxide. After pulsing the oxygen-containing precursor, the reaction chamber may be purged of excess precursor and by-products. In addition, the pulsing of the precursors may use pulsing periods that provide uniform coverage of a monolayer on the surface or may use pulsing periods that provide partial coverage of a monolayer on the surface during a lanthanum/oxygen ALD cycle.
[0070] In an embodiment, ALD TaO may be formed using a number of precursors containing tantalum to provide the tantalum to a substrate for an integrated circuit. Such tantalum-containing precursors include, but are not limited to, Ta(OC2H5)5 and a tantalum halide, such as TaCl4 and TaI4. After pulsing the tantalum-containing precursor and purging the reaction chamber of excess precursor and by-products from pulsing the precursor, an oxygen reactant precursor may be pulsed into the reaction chamber. The oxygen reactant precursor may include, but is not limited to, one or more of water, atomic oxygen, molecular oxygen, ozone, hydrogen peroxide, a water-hydrogen peroxide mixture, alcohol, or nitrous oxide. In addition, the pulsing of the precursors may use pulsing periods that provide uniform coverage of a monolayer on the surface or may use pulsing periods that provide partial coverage of a monolayer on the surface during an ALD cycle forming TaO.
[0071] In various embodiments, nitrogen may be used as a purging gas and a carrier gas for one or more of the sequences. Alternatively, hydrogen, argon gas, or other inert gases may be used as the purging gas. Excess precursor gas and reaction by-products may be removed by the purge gas. Excess precursor gas and reaction by-products may be removed by evacuation of the reaction chamber using various vacuum techniques. Excess precursor gas and reaction by-products may be removed by the purge gas and by evacuation of the reaction chamber.
[0072] FIG. 3 shows a flow diagram of features of an embodiment for forming TaLnON using atomic layer deposition and oxidation. At 310, a layer of TaN is formed by atomic layer deposition. At 320, a layer of LnN is formed by atomic layer deposition on the layer of TaN. TaN and LnN films may be alternately deposited in adjacent layers, in which either nitride layer may be deposited as the starting layer. At 330, the layers of LnN and TaN are annealed. At 340, the annealed layers of LnN and TaN are oxidized to form TaLnON. In an embodiment, the annealing and oxidation may be performed together. The layers of LnN and TaN may be annealed and oxidized by rapid thermal oxidation to form TaLnON.
[0073] In an embodiment, ALD TaN may be formed using a number of precursors containing tantalum to provide the tantalum to a substrate for an integrated circuit. To form tantalum nitride by atomic layer deposition, a tantalum-containing precursor is pulsed onto a substrate in an ALD reaction chamber. A number of precursors containing tantalum may be used to provide the tantalum to a substrate for an integrated circuit. A number of precursors containing tantalum may be used to provide the tantalum to a substrate for an integrated circuit. Precursors containing tantalum may include, but are not limited to, tantalum ethoxide [Ta(OC2H5)5] and tantalum halides, such as TaCl5, TaBr5, and TaF5. In various embodiments, after pulsing the lanthanide-containing precursor and purging the reaction chamber of excess precursor and by-products from pulsing the precursor, a nitrogen reactant precursor may be pulsed into the reaction chamber. The reactant precursor for a tantalum/nitrogen sequence may include, but is not limited to, nitrogen, ammonia (NH3), tert-butylamine (C4H11N), allylamine (C3H7N), 1,1-dimethylhydrazine ((CH3)2NNH2). Other nitrogen reactant precursors that may be used include nitrogen-containing compositions that do not include oxygen. However, nitrogen reactant precursors are not limited to nitrogen-containing compositions that do not include oxygen. Further, forming tantalum nitride by atomic layer deposition is not limited to the abovementioned precursors. In addition, the pulsing of the tantalum precursor may use a pulsing period that provides uniform coverage of a monolayer on the surface or may use a pulsing period that provides partial coverage of a monolayer on the surface during a tantalum sequence.
[0074] In an embodiment, ALD LaN may be formed using a number of precursors containing lanthanum to provide the lanthanum to a substrate for an integrated circuit. Such lanthanum-containing precursors include, but are not limited to, La(thd)3, tris (2,2,6,6-tetramethyl-3,5-heptanedionato)lanthanum (III) tetraglyme adduct, La(EtCp)3, and La(DPM)3. In an embodiment using a La(thd)3 precursor, the substrate may be maintained at a temperature ranging from 180° C. to about 425° C. In an embodiment, H2 may be pulsed along with the La(EtCp)3 precursor or the precursor to reduce carbon contamination in the deposited film. After pulsing the lanthanum-containing precursor and purging the reaction chamber of excess precursor and by-products from pulsing the precursor, a reactant precursor may be pulsed into the reaction chamber. To form LaN, a nitrogen reactant precursor is pulsed. A number of precursors containing nitrogen may be used to provide nitrogen. Such nitrogen-containing precursors include, but are not limited to, nitrogen, ammonia (NH3), tert-butylamine (C4H11N), allylamine (C3H7N), 1,1-dimethylhydrazine ((CH3)2NNH2). In an embodiment, the substrate is maintained at a temperature ranging from about 400° C. to about 500° C. using tert-butylamine or allylamine as a nitrogen precursor. In an embodiment, NH3 may be pulsed with the tert-butylamine and the allylamine. The addition of NH3 may enhance the deposition rate at lower temperatures. In various embodiments, use of the individual lanthanum-containing precursors is not limited to the temperature ranges of the above example embodiments. Further, forming lanthanum nitride by atomic layer deposition is not limited to the abovementioned precursors. In addition, the pulsing of the lanthanum precursor may use a pulsing period that provides uniform coverage of a monolayer on the surface or may use a pulsing period that provides partial coverage of a monolayer on the surface during a lanthanum/nitrogen sequence.
[0075] In various embodiments, nitrogen may be used as a purging gas and a carrier gas for one or more of the sequences. Alternatively, hydrogen, argon gas, or other inert gases may be used as the purging gas. Excess precursor gas and reaction by-products may be removed by the purge gas. Excess precursor gas and reaction by-products may be removed by evacuation of the reaction chamber using various vacuum techniques. Excess precursor gas and reaction by-products may be removed by the purge gas and by evacuation of the reaction chamber.
[0076] FIG. 4 shows a flow diagram of features of an embodiment for forming TaLnON using atomic layer deposition and annealing. At 410, a layer of TaON is formed using atomic layer deposition. At 420, a layer of LnON is formed using atomic layer deposition on the layer of TaON. At 430, the layers of TaON and LnON are annealed to form a layer of TaLnON. TaON and LnON films may be alternately deposited in adjacent layers, in which either oxynitride layer may be deposited as the starting layer.
[0077] In an embodiment, ALD LaON may be formed using a number of precursors containing lanthanum to provide the lanthanum to a substrate for an integrated circuit. Such lanthanum-containing precursors include, but are not limited to, La(thd)3, tris (2,2,6,6-tetramethyl-3,5-heptanedionato)lanthanum (III) tetraglyme adduct, La(EtCp)3, and La(DPM)3. After pulsing the lanthanum-containing precursor and purging the reaction chamber of excess precursor and by-products from pulsing the precursor, a reactant precursor may be pulsed into the reaction chamber. A nitrogen reactant precursor may be pulsed. A number of precursors containing nitrogen may be used to provide nitrogen. Such nitrogen-containing precursors include, but are not limited to, nitrogen, ammonia (NH3), tert-butylamine (C4H11N), allylamine (C3H7N), 1,1-dimethylhydrazine ((CH3)2NNH2). After pulsing the nitrogen-containing precursor and purging the reaction chamber of excess precursor and by-products from pulsing the precursor, an oxygen reactant precursor may be pulsed into the reaction chamber. The oxygen reactant precursor may include, but is not limited to, one or more of water, atomic oxygen, molecular oxygen, ozone, hydrogen peroxide, a water-hydrogen peroxide mixture, alcohol, or nitrous oxide. In various embodiments, the order of pulsing the precursors may vary. In various embodiments, forming lanthanum oxynitride by atomic layer deposition is not limited to the abovementioned precursors. In addition, the pulsing of the precursors may use pulsing periods that provide uniform coverage of a monolayer on the surface or may use pulsing periods that provide partial coverage of a monolayer on the surface during an ALD cycle forming LaON.
[0078] In an embodiment, ALD TaON may be formed using a number of precursors containing tantalum to provide the tantalum to a substrate for an integrated circuit. Such tantalum-containing precursors include, but are not limited to, Ta(OC2H5)5 and one or more tantalum halides. In various embodiments, after pulsing the tantalum-containing precursor and purging the reaction chamber of excess precursor and by-products from pulsing the precursor, a nitrogen reactant precursor may be pulsed into the reaction chamber. The reactant precursor may include, but is not limited to, nitrogen, NH3, C4H11N, C3H7N, and (CH3)2NNH2. Other nitrogen reactant precursors that may be used include nitrogen-containing compositions that do not include oxygen. In various embodiments, the nitrogen-containing precursor may also include oxygen. After pulsing the nitrogen-containing precursor and purging the reaction chamber of excess precursor and by-products from pulsing the precursor, an oxygen reactant precursor may be pulsed into the reaction chamber. The oxygen reactant precursor may include, but is not limited to, one or more of water, atomic oxygen, molecular oxygen, ozone, hydrogen peroxide, a water-hydrogen peroxide mixture, alcohol, or nitrous oxide. In various embodiments, the order of pulsing the precursors may vary. Further, forming tantalum oxynitride by atomic layer deposition is not limited to the abovementioned precursors. In addition, the pulsing of the precursors may use pulsing periods that provide uniform coverage of a monolayer on the surface or may use pulsing periods that provide partial coverage of a monolayer on the surface during an ALD cycle forming TaON.
[0079] In various embodiments, nitrogen may be used as a purging gas and a carrier gas for one or more of the sequences. Alternatively, hydrogen, argon gas, or other inert gases may be used as the purging gas. Excess precursor gas and reaction by-products may be removed by the purge gas. Excess precursor gas and reaction by-products may be removed by evacuation of the reaction chamber using various vacuum techniques. Excess precursor gas and reaction by-products may be removed by the purge gas and by evacuation of the reaction chamber.
[0080] In various embodiments, either before or after forming a TaLnON film, other dielectric layers such as TaO, LnO, TaON, LnON, dielectric nitride layers, dielectric metal silicates, insulating metal oxides, or combinations thereof are formed as part of a dielectric layer or dielectric stack. In an embodiment, these one or more other layers of dielectric material may be provided in stoichiometric form, in non-stoichiometric form, or a combination of stoichiometric dielectric material and non-stoichiometric dielectric material. In an embodiment, depending on the application, a dielectric stack containing a TaLnONx film includes a silicon oxide layer. In an embodiment, the dielectric layer is formed as a nanolaminate. An embodiment of a nanolaminate includes a layer of a tantalum oxide and a TaLnONx film, a layer of tantalum oxynitride and a TaLnONx film, a layer of lanthanide oxide and a TaLnONx film, a layer of lanthanide oxynitride and a TaLnONx film, layers of tantalum oxide, lanthanide oxide, tantalum oxynitride, and lanthanide oxynitride along with a TaLnONx film, or various other combinations. In an embodiment, a dielectric layer is formed substantially as the tantalum lanthanide oxynitride film.
[0081] In various embodiments, the structure of an interface between a dielectric layer and a substrate on which it is disposed is controlled to limit the inclusion of silicon oxide, since a silicon oxide layer would reduce the effective dielectric constant of the dielectric layer. In an embodiment, the material composition and properties for an interface layer are dependent on process conditions and the condition of the substrate before forming the dielectric layer. In an embodiment, though the existence of an interface layer may effectively reduce the dielectric constant associated with the dielectric layer and its substrate, the interface layer, such as a silicon oxide interface layer or other composition interface layer, may improve the interface density, fixed charge density, and channel mobility of a device having this interface layer.
[0082] In an embodiment, a tantalum lanthanide oxynitride layer is doped with other elements. The doping may be employed to enhance the leakage current characteristics of the dielectric layer containing the TaLnONx film by providing a disruption or perturbation of the tantalum lanthanide oxynitride structure. In an embodiment, such doping is realized by substituting a sequence of one of these elements for a tantalum sequence, a lanthanide sequence, or various combinations of sequences. The choice for substitution may depend on the form of the tantalum lanthanide oxynitride structure with respect to the relative amounts of tantalum atoms and lanthanide atoms desired in the oxide. In an embodiment, to maintain a substantially tantalum lanthanide oxynitride, the amount of dopants inserted into the oxynitride are limited to a relatively small fraction of the total number of tantalum and lanthanide atoms.
[0083] After forming a dielectric having a tantalum lanthanide oxynitride layer, other material may be formed upon the tantalum lanthanide oxynitride layer. In an embodiment, the other material is a conductive material. The conductive material may be used as an electrode. Such electrodes may be used as capacitor electrodes, control gates in transistors, or floating gates in floating gate transistors. In an embodiment, the conductive material is a metal or conductive metal nitride. In an embodiment, the conductive material is a conductive semiconductor material. In an embodiment, the conductive material is formed by ALD processes. In an embodiment, the conductive material is formed by a substitution process. In an embodiment, the conductive material is formed in a self-alignment process.
[0084] In various embodiments, a conductive layer may be deposited by atomic layer deposition on a layer of TaLnON or on a dielectric layer containing a layer of TaLnON. A metal layer may be deposited by atomic layer deposition in an ALD cycle having a halide precursor containing the metal to be deposited and a reactant precursor containing hydrogen. Metal layer formation by ALD is not limited to halide precursors and hydrogen reactant precursors. In various embodiments, precursors may be selected to form ALD conductive layers such as aluminum (Al), tungsten (W), molybdenum (Mo), gold (Au), silver (Ag), gold alloy, silver alloy, copper (Cu), platinum (Pt), rhenium (Re), ruthenium (Ru), rhodium (Rh), nickel (Ni), osmium (Os), palladium (Pd), iridium (Ir), cobalt (Co), germanium (Ge), or metallic nitrides such as WN, TiN or TaN. Formation of ALD conductive layers is not limited to the abovementioned materials.
[0085] In an example embodiment, a tantalum layer may be formed on a TaLnON film by atomic layer deposition using a tantalum-containing precursor. In an embodiment, a tantalum halide precursor may be used with hydrogen as a reactant precursor. In an embodiment, a TaCl5 precursor may be used with an atomic hydrogen reactant precursor. The atomic hydrogen reactant precursor may be provided using a plasma. In an embodiment, the substrate temperature may be held at a temperature ranging from about 250° C. to about 400° C. The hydrogen reactant precursor reacts at the substrate to remove the halogen, which forms the selected tantalum halide precursor, leaving tantalum on the substrate surface. After pulsing a tantalum-containing precursor and after pulsing its reactant precursor, the reaction chamber may be purged of excess precursor and/or by-products. In various embodiments, use of the individual tantalum-containing precursors is not limited to the temperature ranges of the above example embodiments. Further, forming tantalum by atomic layer deposition is not limited to the abovementioned precursors. In addition, the pulsing of the tantalum precursor may use a pulsing period that provides uniform coverage of a monolayer on the surface or may use a pulsing period that provides partial coverage of a monolayer on the surface. The tantalum layer may be structured as one or more monolayers. The tantalum layer may have a thickness ranging from a monolayer to thousands of angstroms or more.
[0086] In an embodiment, a metal nitride layer may be deposited by atomic layer deposition using a precursor containing the metal to be deposited and a reactant precursor containing nitrogen in an ALD cycle. In an example embodiment, a titanium nitride layer may be formed with a TaLnON film by atomic layer deposition using a titanium-containing precursor. A nitrogen-containing precursor may be used as the reactant precursor for the titanium-containing precursor. The titanium-containing precursor and the nitrogen-containing precursor may be selected such that their use does not form a titanium oxide in the layer of titanium nitride being formed. The titanium-containing precursor and the nitrogen-containing precursor may be selected such that these precursors do not include oxygen as an elemental component. In an embodiment, a titanium halide precursor may be used with NH3 as a reactant precursor. In an embodiment, a TiCl4 precursor may be used with a NH3 reactant precursor. In an embodiment, the substrate temperature may be held at a temperature ranging from about 380° C. to about 500° C. In an embodiment, the substrate temperature may be held at a temperature less than 600° C. After pulsing a titanium-containing precursor and after pulsing its reactant precursor, the reaction chamber may be purged of excess precursor and/or by-products. In various embodiments, use of the individual titanium-containing precursors is not limited to the temperature ranges of the above example embodiments. Further, forming titanium nitride by atomic layer deposition is not limited to the abovementioned precursors, but may include precursors containing oxygen. In addition, the pulsing of the titanium precursor may use a pulsing period that provides uniform coverage of a monolayer on the surface or may use a pulsing period that provides partial coverage of a monolayer on the surface. The titanium nitride layer may be structured as one or more monolayers. The titanium nitride layer may have a thickness ranging from a monolayer to thousands of angstroms or more.
[0087] FIGS. 5A-5E illustrate an embodiment of a process for forming a metal substituted electrode in place of a previously deposited material on a dielectric containing TaLnON. Though a transistor is discussed with reference to FIGS. 5A-5E , such a process may be used with respect to other embodiments of device configurations. FIG. 5A shows a substrate 501 and shallow trench isolation (STI) regions 502. The substrate 501 can be a semiconductor wafer as well as structures having one or more insulative, semi-insulative, conductive, or semiconductive layers and materials. Thus, for example, the substrate can include silicon-on-insulator, silicon-on-sapphire, and other structures upon which semiconductor devices are formed.
[0088] FIG. 5B further shows a gate dielectric layer 503 formed on the substrate 501, and a gate substitutable layer 504 formed on the gate dielectric layer 503. The gate dielectric layer may include a dielectric layer containing TaLnON in addition to other insulative material or a dielectric layer essentially of TaLnON. The use of such a high-K dielectric increases the capacitance, which is useful for nanoscale integrated circuits. In various embodiments the gate dielectric includes stacked layers comprising one or more high-κ dielectric materials. As described in more detail below, the material of the gate substitutable layer 504 is selected with respect to the desired gate material to allow the gate material to replace the gate substitutable layer. This process forms a gate of the desired gate metal where the substitutable material was positioned on the gate dielectric.
[0089] As shown in FIG. 5C , portions of the gate dielectric layer 503 and the gate substitutable layer 504 are removed to define a gate 505. Sidewalls or spacers 506 are formed along the gate 505. Source/drain regions 507 are also formed. Source/drain regions 507 can be formed using conventional ion implantation and subsequent annealing. These annealing temperatures can pose problems for aluminum gates and other metal gates that have melting temperatures less than the anneal temperature for the source/drain regions.
[0090] FIG. 5D shows an insulative fill layer 508 provided to match the thickness of the gate stack. A planarization procedure, such as chemical-mechanical polishing, can be used to provide an even surface across the fill layer 508 and the gate substitutable layer 504. A metal layer 509, formed of material intended to be the gate material, is deposited over the gate substitutable layer 504 and the fill layer 508. The metal layer 509 is also referred to herein as a layer of gate material. Various deposition processes, such as evaporation, sputtering, chemical vapor deposition, or atomic layer deposition, may be used to form the metal layer 509. The volume of layer 509 is significantly larger than the volume of the substitutable material left on the wafer.
[0091] After the metal layer 509 is deposited on the gate substitutable layer, a metal-substitution reaction is induced. The reaction can be provided by annealing the structure in a non-oxidizing atmosphere such as a nitrogen gas or a forming gas. The heating urges diffusion or dissolution of the intended gate material in metal layer 509 for the substitutable material 504. The substitution process is bounded by the spacers 506 and the gate dielectric 503.
[0092] At the conclusion of the substitution reaction, the residual metal of layer 509 and the substitutable material may be removed such as may be achieved using conventional planarization. FIG. 5E shows the resulting low-resistance gate structure. The illustrated structure includes a metal substituted gate 510 formed by the substitution of the metal of layer 509. The metal substituted gate 510 may include a small amount of the gate substitutable material that did not diffuse above the planarization level 511. Such small amounts of the gate substitutable material do not significantly affect the conductivity of the metal substituted gate 510, and thus do not significantly affect the performance of the device.
[0093] Drain and source contacts (not shown) can be formed, as well as interconnects to other transistors or components, using conventional techniques. Another heat treatment may occur after packaging the integrated circuit in a protective housing in an attempt to reduce the resistivity of the metal gate contacts and other metal interconnections.
[0094] The metal gate substitution technique, as disclosed herein, can be applied to MOS devices, as generally illustrated in FIG. 5E , as well as to form metal floating gates and/or metal control gates in nonvolatile devices. Additionally, various high-κ dielectrics having a TaLnON film can be used between the floating gate and the substrate, and between the control gate and the floating gate in these nonvolatile devices.
[0095] FIG. 6 illustrates a flow diagram of features of an embodiment of a metal substitution technique. At 612, a gate dielectric is formed on a substrate. The gate dielectric includes a TaLnON film. At 613, a layer of gate substitutable material is formed on the gate dielectric. Examples of gate substitutable material include polysilicon, germanium, silicon-germanium, and carbon. At 614, source/drain regions are formed. A layer of gate material is formed at 615 on the gate substitutable material. Examples of such metals include gold, silver, and aluminum. Other metals may be used. At 616, the gate material is substituted for the layer of gate substitutable material.
[0096] A metal substitution reaction substitutes or replaces the substitutable material (e.g. silicon, germanium, silicon-germanium, carbon) with a metal. After the substitution, the resulting gate structure includes substantially all of the desired metal. Small amounts of the substitutable material may remain in the gate structure. The substitution reaction can be induced by heating the integrated circuit assembly to a desired temperature in a vacuum, nitrogen, argon, forming gas or other non-oxidizing atmosphere. Heating causes diffusion of the metal layer 609 into the substitutable layer. The annealing temperature for the substitution is less than the eutectic (lowest melting) temperature of materials involved in the substitution for the reaction for substitution to occur. In an embodiment, to form a gold gate, a metal layer may be formed from gold and annealed at approximately 300° C. to substitute the gold for a silicon substitutable structure. In an embodiment, to form a silver gate, a metal layer may be formed from silver and annealed at approximately 500-600° C. to substitute the silver for a silicon substitutable structure. A polysilicon and germanium substitutable material may be used, which reduces the anneal temperature.
[0097] According to various embodiments, the gate substitutable material 504 shown in FIGS. 5A-5E includes polysilicon. In some embodiments, the gate substitutable material includes germanium. Some embodiments use silicon-germanium with a percentage of silicon in the range from 0% to 100% as the gate substitutable material 504. Some embodiments use carbon as the gate substitutable material 504. With respect to various embodiments which use polysilicon, germanium, or silicon-germanium as the gate substitutable material 504, a replacement metal for the substituted gate may include aluminium, silver, gold, an alloy of silver, an alloy of gold as the replacement metal, or combinations thereof. In various embodiments, with carbon used as the gate substitutable material 504, a replacement metal for the substituted gate may include gold, silver, an alloy of gold, an alloy of silver, copper, platinum, rhenium, ruthenium, rhodium, nickel, osmium, palladium, iridium, cobalt, germanium, or combinations thereof.
[0098] Various embodiments form an integrated circuit structure using two or more substitution reactions. Relatively higher temperature substitution processes can be performed before relatively lower temperature substitution processes. One application for multiple substitution reactions is to independently adjust work functions of NMOS and PMOS transistors in CMOS integrated circuits. Multiple substitution reactions are not limited to this CMOS integrated circuit application. Additional information regarding metal substitution can be found in U.S. patent application Ser. No. 11/176,738 filed Jul. 7, 2005, entitled “METAL-SUBSTITUTED TRANSISTOR GATES,” which is herein incorporated by reference.
[0099] FIGS. 7A-7D illustrate an embodiment of a process for forming a self aligned conductive layer such as a metal gate for a transistor structure. FIG. 7A illustrates a high-κ gate dielectric 710 containing TaLnON formed on a substrate 701. The substrate 701 can be a semiconductor wafer as well as structures having one or more insulative, semi-insulative, conductive, or semiconductive layers and materials. Thus, for example, the substrate can include silicon-on-insulator, silicon-on-sapphire, and other structures upon which semiconductor devices are formed.
[0100] In FIG. 7A , a sacrificial gate 703 is formed of amorphous carbon on the high-κ gate dielectric 710. In various embodiments, an etch barrier 708 is formed over the sacrificial gate and the dielectric. The etch barrier 708 includes silicon nitride or aluminium oxide, and can be formed using a deposition process, according to various embodiments. Sacrificial sidewall spacers 706 are added adjacent the sacrificial gate 703. In various embodiments, the spacers 706 are formed of amorphous carbon by deposition and conventional direct etch techniques. An ion implantation 730 and high temperature anneal are used to form source/drain regions 702 in areas defined by the sacrificial sidewall spacers 706. These annealing temperatures can pose problems for aluminum gates and other metal gates that have melting temperatures less than the anneal temperature for the source/drain regions.
[0101] In FIG. 7B , the sacrificial sidewall spacers (706 in FIG. 7A ) have been removed. Various embodiments use a plasma oxidation process to remove the sacrificial sidewall spacers. In addition, the etch barrier (708 in FIG. 7A ) has been removed. In various embodiments, a light dose ion implantation 740 is used to form source/drain extensions 742 in the substrate 701. The extensions 742 can be annealed at lower temperatures and in shorter times than the more heavily doped source/drain regions 702. According to various embodiments, source/drain extensions for the transistor may be formed with doping the substrate to a depth of 30 nm or less.
[0102] In FIG. 7C , conventional or non-carbon sidewall spacers 756 are formed and the whole structure is back filled with an oxide fill 758, such as silicon dioxide, and planarized. A planarization procedure, such as chemical-mechanical polishing, can be used to provide an even surface. In various embodiments, the conventional sidewall spacers are formed with silicon nitride.
[0103] In FIG. 7D , the sacrificial gate (703 in FIG. 7C ) is removed and replaced by the deposition of a metal layer 760. In various embodiments, the sacrificial gate is removed using a plasma oxidation process. Various deposition processes, such as evaporation, sputtering, chemical vapor deposition, or atomic layer deposition, may be used to form the metal layer 760. The structure is planarized (not shown) using a planarization procedure, such as chemical-mechanical polishing, resulting in the self aligned metal gate over the high-κ gate dielectric insulator 710. Drain and source contacts (not shown) can be formed, as well as interconnects to other transistors or components, using conventional techniques. Another heat treatment may occur after packaging the integrated circuit in a protective housing in an attempt to reduce the resistivity of the metal gate contacts and other metal interconnections.
[0104] FIGS. 7A-7D illustrate two replacement processes for the formation of planar self aligned metal gate transistors, one for disposable sidewall spacers and the other for the gate material itself. The metal gate replacement technique, as disclosed herein, can be applied to MOS devices, as generally illustrated in FIGS. 7A-7D , as well as to form metal floating gates and/or metal control gates in nonvolatile devices. Additionally, various high-κ dielectrics can be used between the floating gate and the substrate, and between the control gate and the floating gate in these nonvolatile devices.
[0105] FIG. 8 illustrates an embodiment of a method 800 for forming a self aligned metal gate on high-κ gate dielectrics containing TaLnON. According to various embodiments, a high-κ gate dielectric containing TaLnON is formed on a substrate, at 802. At 804, a sacrificial carbon gate is formed on the gate dielectric. At 806, sacrificial carbon sidewall spacers are formed adjacent to the sacrificial carbon gate. At 808 source/drain regions for the transistor are formed, using the sacrificial carbon sidewall spacers to define the source/drain regions. The sacrificial carbon sidewall spacers are replaced with non-carbon sidewall spacers at 810. At 812, the sacrificial carbon gate is replaced with a desired metal gate material to provide the desired metal gate material on the gate dielectric.
[0106] In various embodiments, source/drain extensions may be formed after removing the carbon sidewall spacers and before replacing with non-carbon sidewall spacers. An etch barrier is used in various embodiments to separate the sacrificial carbon gate from the sacrificial carbon sidewall spacers. In various embodiments, the carbon sacrificial gate may be replaced with aluminum (Al), tungsten (W), molybdenum (Mo), gold (Au), silver (Ag), gold alloy, silver alloy, copper (Cu), platinum (Pt), rhenium (Re), ruthenium (Ru), rhodium (Rh), nickel (Ni), osmium (Os), palladium (Pd), iridium (Ir), cobalt (Co), germanium (Ge), or metallic nitrides such as WN, TiN or TaN covered by metals. The high-κ gate dielectric formed at 802 may be one of a number of high-κ gate dielectrics containing TaLnON.
[0107] In various embodiments, construction of an integrated circuit structure includes a dielectric containing TaLnON on which is disposed a self-aligned metal electrode. Additional information regarding a self-aligned metal electrode used as a transistor gate can be found in U.S. patent application Ser. No. 11/216,375, filed 31 Aug. 2005, entitled “SELF ALIGNED METAL GATES ON HIGH-K DIELECTRICS,” which is herein incorporated by reference.
[0108] FIG. 9 illustrates an embodiment of a wafer 940 containing integrated circuits having one or more dielectric layers that include a tantalum lanthanide oxynitride film. Conductive electrodes may be disposed on such dielectrics in a number of configurations such as capacitors, transistors, or elements of a memory. The conductive electrodes may be metal electrodes, conductive metal nitride electrodes, and/or conductive metal oxide electrodes. The conductive electrodes may be atomic layer deposited electrodes. Metal electrodes may be metal substituted electrodes and/or self aligned metal electrodes formed in accordance with the teachings of embodiments discussed herein. A common wafer size is 8 inches in diameter. However, wafers are capable of being fabricated in other sizes, and embodiments of wafers containing a tantalum lanthanide oxynitride film are not limited to a particular size. A number of dies can be formed on a wafer. A die 941 is an individual pattern on a substrate that contains circuitry to perform a specific function. A semiconductor wafer typically contains a repeated pattern of such dies containing the same functionality. A die is typically packaged in a protective casing (not shown) with leads extending therefrom (not shown) providing access to the circuitry of the die for communication and control.
[0109] Applications containing electronic devices having dielectric layers containing tantalum lanthanide oxynitride film include electronic systems for use in memory modules, device drivers, power modules, communication modems, processor modules, and application-specific modules, which may include multilayer, multichip modules. Such dielectric layers may be configured as multiple layers containing at least one layer of TaLnON or configured substantially as a TaLnON layer. In addition, such dielectric layers may be configured in contact with a metal electrode. Such circuitry can be a subcomponent of a variety of electronic systems, such as a clock, a television, a cell phone, a personal computer, an automobile, an industrial control system, an aircraft, and others.
[0110] FIG. 10 shows an embodiment of a transistor 1000 having a dielectric layer 1040 containing a TaLnONx film. In an embodiment, transistor 1000 includes a source region 1020 and a drain region 1030 in a silicon-based substrate 1010 where source and drain regions 1020, 1030 are separated by a body region 1032. Body region 1032 defines a channel having a channel length 1034. In an embodiment, a gate dielectric 1040 is disposed on substrate 1010 with gate dielectric 1040 formed as a dielectric layer containing TaLnONX. In an embodiment, gate dielectric 1040 is realized as a dielectric layer formed substantially of TaLnONX. In an embodiment, gate dielectric 1040 is constructed as multiple dielectric layers, that is, as a dielectric stack, containing at least one TaLnONx film and one or more layers of insulating material other than tantalum lanthanide oxynitride film. In an embodiment, the TaLnONx film is structured as one or more monolayers. An embodiment of a TaLnONx film is formed using atomic layer deposition. In an embodiment, gate dielectric 1040 may be realized as a gate insulator in a silicon-based structure.
[0111] In an embodiment, a gate 1050 is formed on and contacts gate dielectric 1040. In an embodiment, gate 1050 includes conductive material. In an embodiment, gate 1050 includes a conductive material structured as one or more monolayers. In an embodiment, the conductive material layer is an ALD conductive material layer. In an embodiment, the conductive material layer is a substituted metal layer. In an embodiment, the conductive material layer is a self-aligned metal layer. In an embodiment, the thickness of the conductive layer ranges from a monolayer to thousands of angstroms or more.
[0112] An interfacial layer may form between body region 1032 and gate dielectric 1040. In an embodiment, an interfacial layer is limited to a relatively small thickness compared to gate dielectric 1040, or to a thickness significantly less than gate dielectric 1040 as to be effectively eliminated. In an embodiment, forming the substrate and the source and drain regions is performed using processes known to those skilled in the art. In an embodiment, the sequencing of the various elements of the process for forming a transistor is conducted with fabrication processes known to those skilled in the art. In an embodiment, transistor 1000 is a MOSFET transistor. In an embodiment, transistor 1000 is a germanium MOSFET structure. In an embodiment, transistor 1000 is a silicon MOSFET structure. In an embodiment, transistor 1000 is a silicon-germanium (SiGe) MOSFET structure. In an embodiment, transistor 1000 is a gallium arsenide MOSFET structure. In an embodiment, transistor 1000 is a NMOS transistor. In an embodiment, transistor 1000 is a PMOS transistor. Transistor 1000 is not limited to the arrangement illustrated in FIG. 10 . For example, transistor 1000 may be structured as a vertical transistor. In various embodiments, use of a gate dielectric containing tantalum lanthanide oxynitride is not limited to silicon-based substrates, but is used with a variety of semiconductor substrates.
[0113] FIG. 11 shows an embodiment of a floating gate transistor 1100 having a dielectric layer containing a TaLnONx film. In an embodiment, the TaLnONx film is structured as one or more monolayers. In an embodiment, the TaLnONx film is formed using atomic layer deposition techniques. In an embodiment, transistor 1100 includes a silicon-based substrate 1110 with a source 1120 and a drain 1130 separated by a body region 1132. Body region 1132 between source 1120 and drain 1130 defines a channel region having a channel length 1134. Located above body region 1132 is a stack 1155 including a gate dielectric 1140, a floating gate 1152, a floating gate dielectric 1142 (integrate dielectric 1142), and a control gate 1150. An interfacial layer may form between body region 1132 and gate dielectric 1140. In an embodiment, such an interfacial layer is limited to a relatively small thickness compared to gate dielectric 1140 or to a thickness significantly less than gate dielectric 1140 as to be effectively eliminated.
[0114] In an embodiment, gate dielectric 1140 includes a dielectric containing an atomic layer deposited TaLnONx film formed in embodiments similar to those described herein. In an embodiment, gate dielectric 1140 is realized as a dielectric layer formed substantially of TaLnONX. In an embodiment, gate dielectric 1140 is a dielectric stack containing at least one TaLnONx film and one or more layers of other insulating materials.
[0115] In an embodiment, floating gate 1152 is formed on and contacts gate dielectric 1140. In an embodiment, floating gate 1152 includes conductive material. In an embodiment, floating gate 1152 is structured as one or more monolayers. In an embodiment, floating gate 1152 is an ALD layer. In an embodiment, floating gate 1152 is a substituted metal layer. In an embodiment, floating gate 1152 is a self-aligned metal layer. In an embodiment, the thickness of the floating gate layer ranges from a monolayer to thousands of angstroms or more.
[0116] In an embodiment, floating gate dielectric 1142 includes a dielectric containing a TaLnONx film. In an embodiment, the TaLnONx film is structured as one or more monolayers. In an embodiment, the TaLnONx is formed using atomic layer deposition techniques. In an embodiment, floating gate dielectric 1142 is realized as a dielectric layer formed substantially of TaLnONX. In an embodiment, floating gate dielectric 1142 is a dielectric stack containing at least one TaLnONx film and one or more layers of other insulating materials.
[0117] In an embodiment, control gate 1150 is formed on and contacts floating gate dielectric 1142. In an embodiment, control gate 1150 includes conductive material. In an embodiment, control gate 1150 is structured as one or more monolayers. In an embodiment, the control gate 1150 is an ALD layer. In an embodiment, control gate 1150 is a substituted metal layer. In an embodiment, control gate 1150 is a self-aligned metal layer. In an embodiment, the thickness of the control gate layer 1150 ranges from a monolayer to thousands of angstroms or more. In an embodiment, control gate 1150 is structured as one or more monolayers.
[0118] In an embodiment, both gate dielectric 1140 and floating gate dielectric 1142 are formed as dielectric layers containing a TaLnONx film structured as one or more monolayers. In an embodiment, control gate 1150 and floating gate 1152 are formed as conductive layers. In an embodiment, the control gate 1150 and floating gate 1152 are structured as one or more monolayers. In an embodiment, control gate 1150 and floating gate 1152 are ALD layers. In an embodiment, control gate 1150 and floating gate 1152 are substituted metal layers. In an embodiment, control gate 1150 and floating gate 1152 are self-aligned metal layers. In an embodiment, gate dielectric 1140, floating gate dielectric 1142, control gate 1150, and floating gate 1152 are realized by embodiments similar to those described herein, with the remaining elements of the transistor 1100 formed using processes known to those skilled in the art. In an embodiment, gate dielectric 1140 forms a tunnel gate insulator and floating gate dielectric 1142 forms an inter-gate insulator in flash memory devices, where gate dielectric 1140 and floating gate dielectric 1142 may include a tantalum lanthanide oxynitride film structured as one or more monolayers. Floating gate transistor 1100 is not limited to the arrangement illustrated in FIG. 11 . For example, floating gate transistor 1100 may be structured as a vertical transistor. Such structures are not limited to silicon-based substrates, but may be used with a variety of semiconductor substrates, such as for but not limited to germanium floating gate transistors, SiGe floating gate transistors, and gallium arsenide floating gate transistors.
[0119] FIG. 12 shows an embodiment of a capacitor 1200 having a dielectric layer containing a tantalum lanthanide oxynitride film 1220 and having an electrode 1230. Embodiments of a tantalum lanthanum oxynitride film 1220 structured as one or more monolayers may also be applied to capacitors in various integrated circuits, memory devices, and electronic systems. In an embodiment for a capacitor 1200 illustrated in FIG. 12 , a method includes forming a first conductive layer 1210, forming a dielectric layer 1220 containing a tantalum lanthanide oxynitride film structured as one or more monolayers on first conductive layer 1210, and forming a second conductive layer 1230 on dielectric layer 1220. In various embodiments, second conductive layer 1230, first conductive layer 1210, or both second and first conductive layers 1230, 1210 are ALD conductive material layers, substituted metal layers, self-aligned metal layers, or a combination thereof. In an embodiment, the thickness of the conductive layer ranges from a monolayer to thousands of angstroms or more.
[0120] In an embodiment, dielectric layer 1220, containing a TaLnON, film, and conductive layers 1210, 1220 are formed using various embodiments described herein. In an embodiment, dielectric layer 1220 is realized as a dielectric layer formed substantially of TaLnONX. In an embodiment, dielectric layer 1220 is a dielectric stack containing at least one TaLnONx film and one or more layers of other insulating materials. Embodiments for a tantalum lanthanide oxynitride film may include, but are not limited to, a capacitor in a DRAM and capacitors in analog, radio frequency (RF), and mixed signal integrated circuits. Mixed signal integrated circuits are integrated circuits that may operate with digital and analog signals.
[0121] FIG. 13 depicts an embodiment of a dielectric structure 1300 having multiple dielectric layers 1305-1, 1305-2 . . . 1305-N, in which at least one layer is a tantalum lanthanide oxynitride layer. In an embodiment, layers 1310 and 1320 provide means to contact dielectric layers 1305-1, 1305-2 . . . 1305-N. In an embodiment, each layer 1310, 1320 or both layers are conductive layers. In an embodiment, layers 1310 and 1320 are electrodes forming a capacitor. In an embodiment, layer 1310 is a body region of a transistor with layer 1320 being a gate. In an embodiment, layer 1310 is a floating gate electrode with layer 1320 being a control gate.
[0122] In an embodiment, dielectric structure 1300 includes one or more layers 1305-1, 1305-2 . . . 1305-N as dielectric layers other than a TaLnON layer, where at least one layer is a TaLnON layer. In an embodiment, dielectric layers 1305-1, 1305-2 . . . 1305-N include a TaO layer, a LnO layer, a TaON layer, a LnON layer, or various combinations of these layers. In an embodiment, dielectric layers 1305-1, 1305-2 . . . 1305-N include an insulating metal oxide layer. In an embodiment, dielectric layers 1305-1, 1305-2 . . . 1305-N include an insulating nitride layer. In an embodiment, dielectric layers 1305-1, 1305-2 . . . 1305-N include an insulating oxynitride layer. In an embodiment, dielectric layers 1305-1, 1305-2 . . . 1305-N include an insulating silicate layer.
[0123] Various embodiments for a dielectric layer containing a tantalum lanthanide oxynitride film structured as one or more monolayers may provide for enhanced device performance by providing devices with reduced leakage current. Such improvements in leakage current characteristics may be attained by forming one or more layers of a tantalum lanthanide oxynitride in a nanolaminate structure with other metal oxides, non-metal-containing dielectrics, or combinations thereof. The transition from one layer of the nanolaminate to another layer of the nanolaminate provides disruption to a tendency for an ordered structure in the nanolaminate stack. The term “nanolaminate” means a composite film of ultra thin layers of two or more materials in a layered stack. Typically, each layer in a nanolaminate has a thickness of an order of magnitude in the nanometer range. Further, each individual material layer of the nanolaminate may have a thickness as low as a monolayer of the material or as high as 20 nanometers. In an embodiment, a TaO/TaLnON nanolaminate contains alternating layers of a TaO and TaLnON. In an embodiment, a TaON/TaLnON nanolaminate contains alternating layers of a TaON and TaLnON. In an embodiment, a LnON/TaLnON nanolaminate contains alternating layers of LNON and TaLnON. In an embodiment, a LnO/TaLnON nanolaminate contains alternating layers of LnO and TaLnON. In an embodiment, a TaO/LnON/LnO/TaON/TaLnON nanolaminate contains various permutations of tantalum oxide layers, lanthanide oxynitride layers, lanthanide oxide layers, tantalum oxynitride layers, and tantalum lanthanide oxynitride layers.
[0124] In an embodiment, the sequencing of the layers in dielectric structure 1300 structured as a nanolaminate depends on the application. The effective dielectric constant associated with nanolaminate structure 1300 is that attributable to N capacitors in series, where each capacitor has a thickness defined by the thickness and composition of the corresponding layer. In an embodiment, by selecting each thickness and the composition of each layer, a nanolaminate structure is engineered to have a predetermined dielectric constant. Embodiments for structures such as nanolaminate structure 1300 may be used as nanolaminate dielectrics in flash memory devices as well as other integrated circuits. In an embodiment, a layer of the nanolaminate structure 1300 is used to store charge in a flash memory device. The charge storage layer of a nanolaminate structure 1300 in a flash memory device may be a silicon oxide layer.
[0125] In an embodiment, transistors, capacitors, and other devices include dielectric films containing a layer of a tantalum lanthanide oxynitride composition with an electrode. In an embodiment, the tantalum lanthanide oxynitride layer is an atomic layer deposited tantalum lanthanide oxynitride layer. In an embodiment, the electrode is an atomic layer deposited electrode. In an embodiment, the electrode is a substituted metal layer. In an embodiment, the electrode is a self-aligned metal layer. In an embodiment, dielectric films containing a tantalum lanthanide oxynitride layer with an electrode are implemented into memory devices and electronic systems including information handling devices. In various embodiments, information handling devices include wireless systems, telecommunication systems, and computers. In various embodiments, such electronic devices and electronic apparatus are realized as integrated circuits.
[0126] FIG. 14 illustrates a block diagram for an electronic system 1400 with one or more devices having a dielectric structure including a TaLnONx film with an electrode. Electronic system 1400 includes a controller 1405, a bus 1415, and an electronic device 1425, where bus 1415 provides electrical conductivity between controller 1405 and electronic device 1425. In various embodiments, controller 1405 includes an embodiment of a TaLnONx film with an electrode. In various embodiments, electronic device 1425 includes an embodiment of a TaLnONx film with an electrode. In various embodiments, controller 1405 and electronic device 1425 include embodiments of a TaLnONx film with an electrode. In an embodiment, electronic system 1400 includes, but is not limited to, fiber optic systems, electro-optic systems, and information handling systems such as wireless systems, telecommunication systems, and computers.
[0127] FIG. 15 depicts a diagram of an embodiment of a system 1500 having a controller 1505 and a memory 1525. In an embodiment, controller 1505 includes a TaLnON film with an electrode. In an embodiment, memory 1525 includes a TaLnON film structured as one or more monolayers with an electrode. In an embodiment, controller 1505 and memory 1525 each include a TaLnON film with an electrode. In an embodiment, system 1500 also includes an electronic apparatus 1535 and a bus 1515, where bus 1515 provides electrical conductivity between controller 1505 and electronic apparatus 1535 and between controller 1505 and memory 1525. In an embodiment, bus 1515 includes an address bus, a data bus, and a control bus, each independently configured. In an alternative embodiment, bus 1515 uses common conductive lines for providing one or more of address, data, or control, the use of which is regulated by controller 1505. In an embodiment, electronic apparatus 1535 is additional memory configured in a manner similar to memory 1525. In an embodiment, additional peripheral device or devices 1545 are coupled to bus 1515. In an embodiment, peripheral devices 1545 include displays, additional storage memory, or other control devices that may operate in conjunction with controller 1505. In an alternative embodiment, peripheral devices 1545 may include displays, additional storage memory, or other control devices that may operate in conjunction with memory 1525, or controller 1505 and memory 1525. In an embodiment, controller 1505 is a processor. In an embodiment, one or more of controller 1505, memory 1525, bus 1515, electronic apparatus 1535, or peripheral devices 1545 include an embodiment of a dielectric layer having a TaLnON film structured as one or more monolayers with an electrode. In an embodiment, system 1500 includes, but is not limited to, information handling devices, telecommunication systems, and computers.
[0128] In an embodiment, memory 1525 is realized as a memory device containing a TaLnON film structured as one or more monolayers with an electrode. In an embodiment, a TaLnON structure with a conductive layer is formed in a memory cell of a memory array. In an embodiment, such a structure is formed in a capacitor in a memory cell of a memory array. In an embodiment, such a structure is formed in a transistor in a memory cell of a memory array. In an embodiment, it will be understood that embodiments are equally applicable to any size and type of memory circuit and are not intended to be limited to a particular type of memory device. Memory types include a DRAM, SRAM (Static Random Access Memory) or Flash memories. Additionally, the DRAM could be a synchronous DRAM commonly referred to as SGRAM (Synchronous Graphics Random Access Memory), SDRAM (Synchronous Dynamic Random Access Memory), SDRAM II, and DDR SDRAM (Double Data Rate SDRAM), as well as other emerging DRAM technologies.
[0129] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments shown. Various embodiments use permutations and/or combinations of embodiments described herein. It is to be understood that the above description is intended to be illustrative, and not restrictive, and that the phraseology or terminology employed herein is for the purpose of description and not of limitation.
Claims
What is claimed is:
1. An electronic device comprising:
a substrate; and
a dielectric disposed on the substrate, the dielectric including a layer of TaLnON, the layer of TaLnON having a layered structure of one or more monolayers.
2. The electronic device of claim 1, wherein the electronic device includes a metal electrode disposed upon and contacting the dielectric layer.
3. The electronic device of claim 1, wherein the dielectric consists essentially of the TaLnON layer.
4. The electronic device of claim 1, wherein the electronic device includes contacts to couple the electronic device to other apparatus of a system.
5. The electronic device of claim 1, wherein the layer of TaLnON includes approximately 30 atomic % oxygen and nitrogen in a range from approximately 30 atomic % to 35 atomic %.
6. An electronic device comprising:
a substrate;
a first conductive layer disposed above the substrate:
a dielectric disposed on the first conductive layer, the dielectric including a layer of TaLnON, the layer of TaLnON having a layered structure of one or more monolayers; and
a second conductive layer disposed on the dielectric such that the dielectric is configured as a capacitor dielectric in a capacitor with the first and second conductive layers.
7. The electronic device of claim 6, wherein the dielectric includes one or more insulating layers in addition to the layer of TaLnON.
8. The electronic device of claim 6, wherein at least one of the first or second conductive layers comprises a metal layer.
9. The electronic device of claim 6, wherein the capacitor is disposed in a radio frequency circuit.
10. The electronic device of claim 6, wherein the capacitor is disposed in a mixed signal integrated circuit.
11. An electronic device comprising:
a substrate; and
a dielectric disposed, above the substrate, in a transistor, the dielectric including a layer of TaLnON, the layer of TaLnON having a layered structure of one or more monolayers.
12. The electronic device of claim 11, wherein the dielectric is disposed as a tunnel gate insulator on a channel between a source and a drain of the transistor.
13. The electronic device of claim 11, wherein the transistor includes a self-aligned metal gate between non-carbon spacers, the self-aligned metal gate disposed on the dielectric.
14. The electronic device of claim 11, wherein the transistor includes a metal substituted gate disposed on the dielectric.
15. The electronic device of claim 14, wherein the metal substituted gate includes at least one of gold, silver, an alloy of gold, an alloy of silver, copper, platinum, rhenium, ruthenium, rhodium, nickel, osmium, palladium, iridium, cobalt, or germanium, or combinations thereof.
16. An electronic device comprising:
a substrate; and
a dielectric disposed in a memory configured on the substrate, the dielectric including a layer of TaLnON, the layer of TaLnON having a layered structure of one or more monolayers.
17. The electronic device of claim 16, wherein the dielectric is structured as a nanolaminate.
18. The electronic device of claim 16, wherein the nanolaminate includes a silicon oxide layer to store charge in the memory configured as a flash memory device.
19. The electronic device of claim 16, wherein the dielectric is disposed in a capacitor in a memory cell of the memory.
20. The electronic device of claim 16, wherein Ln is a lanthanide different from lanthanum.
21. An electronic device comprising:
a substrate;
a dielectric disposed on the substrate, the dielectric including a layer of TaLnON, the layer of TaLnON having a layered structure of one or more monolayers; and
a conductive layer disposed in contact with the dielectric, the conductive layer having a layered structure of one or more monolayers.
22. The electronic device of claim 21, wherein the conductive layer includes at least one of aluminum, tungsten, molybdenum, gold, silver, gold alloy, silver alloy, copper, platinum, rhenium, ruthenium, rhodium, nickel, osmium, palladium, iridium, cobalt, germanium, or one or more metallic nitrides, or combinations thereof.
23. The electronic device of claim 21, wherein the layer of TaLnON includes one or more dopants, the dopants selected from elements or compounds other than tantalum, lanthanide, oxygen, and nitrogen.
24. The electronic device of claim 21, wherein the TaLnON is configured having more tantalum than lanthanide in the TaLnON.
25. The electronic device of claim 21, wherein the layer of TaLnON includes approximately 30 atomic % oxygen and approximately 30 atomic % nitrogen.
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