Method of enabling seamless cobalt gap-fill

[0001] This application claims benefit of U.S. provisional patent application No. 61/616,842, filed Mar. 28, 2012, which is hereby incorporated by reference.

[0002] 1. Field of the Invention

[0003] Embodiments of the invention generally relate to the field of semiconductor manufacturing processes, more particularly, to methods for depositing a contact metal layer in contact structures of a semiconductor device.

[0004] 2. Description of the Related Art

[0005] Integrated circuits may include more than one million micro-electronic field effect transistors (e.g., complementary metal-oxide-semiconductor (CMOS) field effect transistors) that are formed on a substrate (e.g., semiconductor wafer) and cooperate to perform various functions within the circuit. Reliably producing sub-half micron and smaller features is one of the key technologies for the next generation of very large scale integration (VLSI) and ultra large-scale integration (ULSI) of semiconductor devices. However, as the limits of integrated circuit technology are pushed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on processing capabilities. Reliable formation of the gate pattern is important to integrated circuits success and to the continued effort to increase circuit density and quality of individual substrates and die.

[0006] As feature sizes have become smaller, the demand for higher aspect ratios, defined as the ratio between the depth of the feature and the width of the feature, has steadily increased to 20:1 and even greater. A variety of problems may occur when depositing contact metal layers into contact structures with small geometries, such as geometries having aspect ratios of about 20:1 or smaller. For example, a contact metal layer deposited using a conventional PVD process often suffers from poor step coverage, overhang, and voids formed within the via or trench when the via has a critical dimension of less than 50 nm or has an aspect ratio greater than 10:1. Insufficient deposition on the bottom and sidewalls of the vias or trenches can also result in deposition discontinuity, thereby resulting in device shorting or poor interconnection formation. Furthermore, the contact metal layer may have poor adhesion over the underlying silicon containing layer, resulting in peeling of the contact metal layer from the substrate and the subsequent conductive metal layer.

[0007] With this increase in transistor density and subsequent decrease in the cross-sections of metal-contacts, meeting the contact resistance requirements using existing low resistivity tungsten (W) integration schemes has become quite challenging. The necessity of high-resistivity adhesion (e.g., B₂H₆ nucleation) and barrier layers (e.g., TiN) in the tungsten contact integration scheme results in increased contact resistance making it an unattractive option for technology nodes less than 22 nanometers.

[0008] Therefore, there is a need for an improved method for forming a contact metal layer in high aspect ratio features.

[0009] Embodiments of the invention generally relate to the field of semiconductor manufacturing processes, more particularly, to methods for depositing a contact metal layer in contact structures of a semiconductor device. In certain embodiments, a method for depositing a contact metal layer for forming a contact structure in a semiconductor device is provided. The method comprises performing a cyclic metal deposition process to deposit a contact metal layer on a substrate and annealing the contact metal layer disposed on the substrate. The cyclic metal deposition process comprises exposing the substrate to a deposition precursor gas mixture to deposit a portion of the contact metal layer on the substrate, exposing the portion of the contact metal layer to a plasma treatment process, and repeating the exposing the substrate to a deposition precursor gas mixture and exposing the portion of the contact metal layer to a plasma treatment process until a predetermined thickness of the contact metal layer is achieved.

[0010] In certain embodiments, a method for depositing a contact metal layer for forming a contact structure in a semiconductor device is provided. The method comprises performing a barrier layer deposition process to deposit a barrier layer on a substrate, performing a wetting layer deposition to deposit a wetting layer on the substrate, and performing a cyclic metal deposition process to deposit a contact metal layer on the substrate. The cyclic metal deposition process comprises exposing the substrate to a deposition precursor gas mixture to deposit a portion of the contact metal layer on the substrate and repeating the exposing the substrate to a deposition precursor gas mixture and exposing the portion of the contact metal layer to a plasma treatment process until a predetermined thickness of the contact metal layer is achieved. The method further provides for annealing the contact metal layer disposed on the substrate.

[0011] In certain embodiments, a method for depositing a contact metal layer for forming a contact structure in a semiconductor device is provided. The method comprises performing a barrier layer deposition process to deposit a barrier layer on a substrate, performing a wetting layer deposition process to deposit a wetting layer on the substrate, and performing an annealing process on the wetting layer. The method further comprises performing a metal deposition process to deposit a contact metal layer on the substrate by exposing the contact metal layer to a deposition precursor gas mixture to deposit a portion of the contact metal layer on the substrate. Finally, the method comprises exposing the portion of the contact metal layer to a plasma treatment process and annealing the contact metal layer disposed on the substrate.

[0021] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0022] Embodiments of the present invention provide gap-fill utilizing metallic CVD processes (e.g., cobalt CVD processes) resulting in a potential low contact resistance (Rc) one-material solution for contact fill. The CVD films deposited according to embodiments described herein have conformal step coverage and low surface roughness. Further, the embodiments demonstrated herein demonstrate a process for filling contact holes of a semiconductor device with no seam formation.

[0023] In one embodiment, a method for depositing a contact metal layer over a substrate is provided which includes exposing the substrate to a cobalt precursor gas and hydrogen gas to selectively form a portion of a seamless gap fill cobalt layer within a feature, and exposing the cobalt layer to a plasma and a reagent, such as nitrogen, ammonia, hydrogen, an ammonia/nitrogen mixture, or combinations thereof during a post-treatment process.

[0024] As will be explained in greater detail below, a contact metal layer is deposited on a substrate to form a contact metal structure on the substrate. The term “substrate” as used herein refers to a layer of material that serves as a basis for subsequent processing operations and includes a surface to be disposed for forming a contact metal layer thereon. The substrate may be a material such as crystalline silicon (e.g., Si<100> or Si<111>), silicon oxide, strained silicon, silicon germanium, doped or undoped polysilicon, doped or undoped silicon wafers, patterned or non-patterned wafers silicon on insulator (SOI), carbon doped silicon oxides, silicon nitride, doped silicon, germanium, gallium arsenide, glass, or sapphire. The substrate can also include one or more nonconductive materials, such as silicon, silicon oxide, doped silicon, germanium, gallium arsenide, glass, and sapphire. The substrate can also include dielectric materials such as silicon dioxide, organosilicates, and carbon doped silicon oxides. Further, the substrate can include any other materials such as metal nitrides and metal alloys, depending on the application.

[0025] In one or more embodiments, the substrate can form a gate structure including a gate dielectric layer and a gate electrode layer to facilitate connecting with an interconnect feature, such as a plug, via, contact, line, and wire, subsequently formed thereon. The substrate may have various dimensions, such as 200 mm, 300 mm, or 450 mm diameter wafers or other dimensions, as well as rectangular or square panels. Unless otherwise noted, embodiments and examples described herein may be conducted on substrates with a 200 mm diameter, a 300 mm diameter, or a 450 mm diameter, particularly a 300 mm diameter.

[0026] The term “contact structure” as used herein refers to a layer of material that includes a contact metal layer that can form part of a gate electrode. In one or more embodiments, the contact metal layer can be nickel layer, cobalt layer, titanium layer or any combinations thereof.

[0027] Moreover, the substrate is not limited to any particular size or shape. The substrate can be a round wafer having a 200 mm diameter, a 300 mm diameter or other diameters, such as 450 mm, among others. The substrate can also be any polygonal, square, rectangular, curved or otherwise non-circular workpiece, such as a polygonal glass substrate used in the fabrication of flat panel displays.

[0028] Embodiments described herein provide methods for depositing/forming a contact metal layer on a substrate to form a contact structure. The deposition process may efficiently improve deposited film step coverage, conformality, and continuity and uniformity across the substrate, thereby improving the overall film properties formed across the substrate.

[0029] FIG. 1 illustrates a processing chamber 150 that may be used to form contact metal materials by vapor deposition processes as described herein. The contact metal materials may contain metallic cobalt, metallic nickel, derivatives thereof, or combinations thereof. A processing chamber 150 may be used to perform CVD, plasma enhanced-CVD (PE-CVD), pulsed-CVD, ALD, PE-ALD, derivatives thereof, or combinations thereof. Water channels, such as a convolute liquid channel 162, may be used to regulate the temperature of a lid assembly 100 during the vapor deposition process for depositing a cobalt-containing material. In one embodiment, the lid assembly 100 may be heated or maintained at a temperature within a range from about 100° C. to about 300° C., preferably, from about 125° C. to about 225° C., and more preferably, from about 150° C. to about 200° C. The temperature is maintained during the vapor deposition process of a cobalt-containing material and/or nickel containing material.

[0030] A showerhead 156 has a relatively short upwardly extending rim 158 screwed to a gas box plate 160. Both the showerhead 156 and the gas box plate 160 may be formed from or contain a metal, such as aluminum, stainless steel, or alloys thereof. The convolute liquid channel 162 is formed in the top of the gas box plate 160 and covered and sealed by a water cooling cover plate 134. Water is generally flown through the convolute liquid channel 162. However, alcohols, glycol ethers, and other organic solvents may be used solely or mixed with water to transfer heat away from or to the lid assembly 100. The convolute liquid channel 162 is formed in a serpentine though generally circumferential path having bends (e.g., three sharp U-turns or U-shaped bends) as the path progresses from the inside to the outside until the path returns to the inside in a radial channel (not shown). The convolute liquid channel 162 is narrow enough to ensure that the flow of water becomes turbulent, thus aiding the flow of heat from the flange of the gas box plate 160 to the water in the convolute liquid channel 162. A liquid temperature regulating system (not shown) may be attached to the convolute liquid channel 162 and used to transfer heat away from or to lid assembly 100. In one example, the lid assembly 100 is configured to be heated or maintained at a temperature of about 150° C. and is in fluid communication with a source of a cobalt precursor, such as dicobalt hexacarbonyl butylacetylene “CCTBA,” and a source of a hydrogen precursor, such as H₂.

[0031] The extending rim 158 of the showerhead 156 is attached to the bottom rim 171 of the gas box plate 160. Both rims 158 and 171 are maximally sized between encompassing a lid isolator 175 and an encompassed lower cavity 130 of the showerhead 156. A screw fastening between the showerhead 156 and the gas box plate 160 ensures good thermal contact over the maximally sized contact area. The thermal flow area extends from the outside at the lid isolator 175 (except for a gap between the lid isolator 175 and either the showerhead 156 or the gas box plate 160) to the inside at a lower cavity 130. The structure of the convolute liquid channels 162 provides efficient thermal transfer between the water and the gas box plate 160. The mechanical interface between the flange of gas box plate 160 and showerhead 156 ensures efficient thermal transfer between the gas box plate 160 and the showerhead 156. Accordingly, cooling of the showerhead 156 is greatly enhanced.

[0032] The processing chamber 150 further contains a heater pedestal 152 connected to a pedestal stem 154 that may be vertically moved within the processing chamber 150. The heater portion of the heater pedestal 152 may be formed of a ceramic material. In its upper deposition position, the heater pedestal 152 holds a substrate 402 in close opposition to a lower surface 107 of the showerhead 156. A processing region 126 is defined between the heater pedestal 152 and the lower surface 107 of the showerhead 156. The showerhead 156 has a plurality of apertures or holes 109 communicating between the lower cavity 130 and the processing region 126 to allow for the passage of processing gas. The processing gas is supplied through the gas port 132 formed at the center of the water-cooled gas box plate 160 which is made of aluminum. The upper side of the gas box plate 160 is covered by a water cooling cover plate 134 surrounding the upper portion of the gas box plate 160 that includes a gas port 132. The gas port 132 supplies the processing gases to an upper cavity 138 which is separated from the lower cavity 130 by a blocker plate 140. The blocker plate 140 has a large number of holes 109 disposed therethrough. In one embodiment, the cavities 130 and 138, showerhead 156, and blocker plate 140 evenly distribute the processing gas over the upper face of the substrate 402.

[0033] The substrate 402 may be supported on the heater pedestal 152, which is illustrated in a raised, deposition position. In a lowered, loading position, a lifting ring 116 is attached to a lift tube 117 which lifts four lift pins 118. The lift pins 118 fit to slide into the heater pedestal 152 so that the lift pins 118 can receive the substrate 402 loaded into the chamber through a loadlock port 119 in a chamber body 120. In one embodiment, the heater pedestal 152 may contain an optional confinement ring 110, such as during plasma-enhanced vapor deposition processes.

[0034] A side purge gas source 123 may be coupled to the processing chamber 150 and configured to supply purge gas to an edge portion 151 of the substrate 402 as needed. In one embodiment, the gases may be supplied from the side purge gas source 123 to the substrate 402 edge portion 151. The gasses may be a hydrogen gas, argon gas, nitrogen gas, helium gas, combinations thereof, or the like. Furthermore, a bottom purge gas source 125 may also be coupled to the chamber 150 to supply the purge gas from the bottom of the chamber 150 to the substrate 402 surface. Similarly, the purge gas supplied from the bottom purge gas source 125 may include a hydrogen gas, argon gas, nitrogen gas, helium gas, combinations thereof, or the like.

[0035] A lid isolator 175 is interposed between showerhead 156 and a lid rim 166, which can be lifted off the chamber body 120 to open the processing chamber 150 for maintenance access. The vacuum within processing chamber 150 is maintained by a vacuum pump 170 connected to a pump plenum 172 within the processing chamber 150, which connects to an annular pumping channel 174.

[0036] An annular chamber liner 179 made of quartz is disposed in the processing chamber 150 which defines a side of the annular pumping channel 174 but also partially defines a further choke aperture 181 disposed between the processing region 126 and the annular pumping channel 174. The annular chamber liner 179 also supports the confinement ring 110 in the lowered position of the heater pedestal 152. The chamber liner 179 also surrounds a circumference at the back of the heater pedestal 152. The chamber liner 179 rests on a narrow ledge in chamber body 120, but there is little other contact, so as to minimize thermal transport. Below the chamber liner 179 is located a Z-shaped lower chamber shield 121, made of opaque quartz. The lower chamber shield 121 rests on the bottom of chamber body 120 on an annular boss 177 formed on the bottom of the lower chamber shield 121. The quartz prevents radiative coupling between the bottom of the heater pedestal 152 and the chamber body 120. The annular boss 177 minimizes conductive heat transfer to the chamber body 120. In an alternative embodiment, the lower chamber shield 121 includes an inwardly extending bottom lip joined to a conically shaped upper portion conforming to the inner wall of chamber body 120. While this alternative design is operationally satisfactory, the sloping shape is much more expensive to fabricate in quartz.

[0037] In one embodiment, a remote plasma source 141 may be coupled to the processing chamber 150 through a gas port 132 to supply reactive plasma from the remote plasma source 141 through the plurality of holes 109 in the showerhead 156 to the processing chamber 150 to the substrate 402 surface. It is noted that the remote plasma source 141 may be coupled to the processing chamber 150 in any suitable position to supply a reactive remote plasma source to the substrate 402 surface as needed. Suitable gases that may be supplied to the remote plasma source 141 to be dissociated and further delivered to the substrate 402 surface include hydrogen, argon, helium, nitrogen, ammonia, combinations thereof and the like.

[0038] In FIG. 1, a control unit 180 may be coupled to the chamber 150 to control processing conditions. The control unit 180 comprises a central processing unit (CPU) 182, support circuitry 184, and memory 186 containing associated control software 183. The control unit 180 may be one of any form of a general purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The CPU 182 may use any suitable memory 186, such as random access memory, read only memory, floppy disk drive, compact disc drive, hard disk, or any other form of digital storage, local or remote. Various support circuits may be coupled to the CPU 182 for supporting the chamber 150. The control unit 180 may be coupled to another controller that is located adjacent individual chamber components. Bi-directional communications between the control unit 180 and various other components of the chamber 150 are handled through numerous signal cables collectively referred to as signal buses, some of which are illustrated in FIG. 1.

[0039] FIG. 2 is a schematic top view diagram of an illustrative multi-chamber processing system 200 that can be adapted to perform a metal layer deposition process as disclosed herein having a processing chamber 80, such as the chamber 150 described above in reference to FIG. 1, integrated therewith. The system 200 can include one or more load lock chambers 202 and 204 for transferring substrates 90 into and out of the system 200. Generally, the system 200 is maintained under vacuum and the load lock chambers 202 and 204 can be “pumped down” to introduce substrates 90 introduced into the system 200. A first robot 210 can transfer the substrates 90 between the load lock chambers 202 and 204, and a first set of one or more substrate processing chambers 212, 214, 216, and 80. Each processing chamber 212, 214, 216, and 80 is configured to be at least one of a substrate deposition process, such as cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, degas, pre-cleaning orientation, anneal, and other substrate processes. Furthermore, one of the processing chamber 212, 214, 216, and 80 may also be configured to perform a pre-clean process prior to performing a deposition process or a thermal annealing process on the substrate 90. The position of the processing chamber 80 utilized to perform a thermal annealing process relative to the other chambers 212, 214, 216 is for illustration, and the position of the processing chamber 80 may be optionally be switched with any one of the processing chambers 212, 214, 216 if desired.

[0040] The first robot 210 can also transfer substrates 90 to/from one or more transfer chambers 222 and 224. The transfer chambers 222 and 224 can be used to maintain ultrahigh vacuum conditions while allowing substrates 90 to be transferred within the system 200. A second robot 230 can transfer the substrates 90 between the transfer chambers 222 and 224 and a second set of one or more processing chambers 232, 234, 236 and 238. Similar to the processing chambers 212, 214, 216, and 80, the processing chambers 232, 234, 236, and 238 can be outfitted to perform a variety of substrate processing operations including the dry etch processes described herein in addition to cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, degas, and orientation, for example. Any of the substrate processing chambers 212, 214, 216, 232, 234, 236, and 238 can be removed from the system 200 if not necessary for a particular process to be performed by the system 200. After the preclean, deposition and/or a thermal annealing process is performed in the processing chamber 80, the substrate may further be transferred to any of the processing chambers 212, 214, 216, 232, 234, 236, and 238 of the system 200 to perform other process as needed.

[0041] FIG. 3 illustrates a flow diagram of one embodiment of a process sequence 300 used to deposit a contact metal layer in a semiconductor device structure on a substrate. The sequence described in FIG. 3 corresponds to the fabrication stages depicted in FIGS. 4A-4E, which are discussed below. FIGS. 4A-4E illustrate schematic cross-sectional views of a substrate 402 having a device structure 408 formed thereon during different stages of fabricating a contact metal layer 420 on the device structure 408 illustrated by the processing sequence 300. The sequence of FIG. 3 is generally provided with reference to a CVD, ALD, or PVD deposited cobalt contact metal layer.

[0042] Possible integration schemes include but are not limited to: (a) PVD Ti+ALD TiN; (b) PVD Ti+CVD Co; (c) CVD Co; and (d) CVD Co+PVD Co. PVD Ti provides good electrical contact with underlying silicide at source or drain. ALD TiN improves adhesion of the cobalt film, if needed to help re-flow of the cobalt film. CVD Co: cobalt fill using CVD films or CVD followed by re-flow.

[0043] The process sequence 300 starts at block 310 by providing a substrate, such as the substrate 402 depicted in FIG. 4A, into the processing chamber, such as the substrate 402 disposed in the processing chamber 150 depicted in FIG. 1, or other suitable processing chamber. The substrate 402 shown in FIG. 4A includes a semiconductor device structure 408 (e.g., such as a gate structure or other structures configured to form a contact structure) formed on the substrate 402. It is noted that this particular device structure 408 may be used in three-dimensional (3-D) flash memory applications, DRAM applications, or other suitable applications with high aspect ratio or other odd geometries.

[0044] A silicon containing layer 404 is formed on the substrate 402 having openings 406 formed therein with high aspect ratios, such as aspect ratios greater than 10:1, for example about greater than 20:1. The openings 406 (which may be a contact opening, contact via, contact trench, contact channel or the like) are formed in the device structure 408 and have sidewalls 412 and a bottom 414 which form an open channel to expose the underlying silicon containing layer 404. The silicon containing layer 404 may include any suitable layers such as a single silicon layer or a multiple layer film stack having at least one silicon containing layer formed therein. In the embodiment wherein the silicon containing layer 404 is in the form of a single layer, the silicon containing layer 404 may be a silicon oxide layer, an oxide layer, a silicon nitride layer, a nitride layer, a silicon oxynitride layer, a titanium nitride layer, a polysilicon layer, a microcrystalline silicon layer, a monocrystalline silicon, a doped polysilicon layer, a doped microcrystalline silicon layer, or a doped monocrystalline silicon.

[0045] In another example, the silicon containing layer 404 may be a film stack including a composite oxide and nitride layer, at least one or more oxide layers sandwiching a nitride layer, and combinations thereof. Suitable dopants doped in the silicon containing layer 404 may include p-type dopants and n-type dopants, such as boron (B) containing dopants or phosphine (P) containing dopants. In one embodiment wherein the silicon containing layer 404 is in form of a multiple film stack having at least one silicon containing layer, the silicon containing layer 404 may include repeating pairs of layers including a silicon containing layer and a dielectric layer. In one embodiment, the silicon containing layer 404 may include a polysilicon layer and/or other metal materials and/or a dielectric layer disposed therein. Suitable examples of the dielectric layer may be selected from a group consisting of an oxide layer, silicon oxide layer, a silicon nitride layer, a nitride layer, titanium nitride layer, a composite of oxide and nitride layer, at least one or more oxide layers sandwiching a nitride layer, and combinations thereof, among others.

[0046] Prior to transferring the substrate 402 into the metal deposition processing chamber described at block 310, a pre-cleaning process is optionally performed to treat the substrate surfaces 411, sidewalls 412 and bottoms 414 of the openings 406 to remove native oxides or other sources of contaminants. Removal of native oxides or other sources of contaminants from the substrate 402 may provide a low contact resistance surface to form a good contact surface for forming a contact metal layer.

[0047] The pre-cleaning process performed includes supplying a pre-cleaning gas mixture into a pre-cleaning chamber. The pre-cleaning chamber may be a Preclean PCII, PCXT or Siconi™ chambers which are available from Applied Materials, Inc., Santa Clara, Calif. The pre-cleaning chamber may be incorporated in the illustrative multi-chamber processing system 200 and may be configured to be one of the processing chamber 212, 214, 216, 232, 234, 236, 238 of the system 200 as needed. It is noted that other pre-cleaning chambers available from other manufactures may also be utilized to practice the embodiments described herein.

[0048] The pre-cleaning process is performed by supplying a cleaning gas mixture into the pre-cleaning processing chamber incorporated in the system 200 to form a plasma from the pre-cleaning gas mixture for removing the native oxide. In one embodiment, the pre-cleaning gas mixture used to remove native oxides is a mixture of ammonia (NH₃) and nitrogen trifluoride (NF₃) gases. The amount of each gas introduced into the processing chamber may be varied and adjusted to accommodate, for example, the thickness of the native oxide layer to be removed, the geometry of the substrate being cleaned, the volume capacity of the plasma, the volume capacity of the chamber body, as well as the capabilities of the vacuum system coupled to the chamber body.

[0049] In one or more embodiments, the gases added to provide a pre-cleaning gas mixture having at least a 1:1 molar ratio of ammonia (NH₃) to nitrogen trifluoride (NF₃). In one or more embodiments, the molar ratio of the pre-cleaning gas mixture is at least about 3:1 (ammonia to nitrogen trifluoride). The gases are introduced at a molar ratio of from about 5:1 (ammonia to nitrogen trifluoride) to about 30:1. In yet another embodiment, the molar ratio of the gas mixture is from about 5:1 (ammonia to nitrogen trifluoride) to about 10:1. The molar ratio of the pre-cleaning gas mixture can also fall between about 10:1 (ammonia to nitrogen trifluoride) and about 20:1.

[0050] A purge gas or carrier gas can also be added to the pre-cleaning gas mixture. Any suitable purge/carrier gas can be used, such as argon, helium, hydrogen, nitrogen, or mixtures thereof. The overall pre-cleaning gas mixture is from about 0.05% to about 20% by volume of ammonia and nitrogen trifluoride. The remainder of the pre-cleaning gas mixture may be the purge/carrier gas.

[0051] The operating pressure within the pre-clean chamber can be varied. The pressure may be maintained between about 1 Torr and about 10 Torr. A RF source power may be applied to maintain a plasma in the cleaning gas mixture. For example, a power of about 15 Watts to about 100 Watts may be applied to maintain a plasma inside the pre-cleaning processing chamber. The frequency at which the power is applied is about 350 kHz. The frequency can range from about 50 kHz to about 350 kHz. The plasma energy dissociates the ammonia and nitrogen trifluoride gases into reactive species, e.g., fluorine radicals and/or hydrogen radicals that combine to form a highly reactive ammonia fluoride (NH₄F) compound and/or ammonium hydrogen fluoride (NH₄F.HF) in the gas phase. These molecules are then delivered from the plasma location to the substrate surface to be cleaned. A purge/carrier gas can be used to facilitate the delivery of the reactive species to the substrate. In one embodiment, a titanium layer may be deposited after the pre-cleaning process. The titanium layer operates to gather any remaining oxygen at the interface of the via and the underlying substrate which provides for improved electrical contact with the underlying substrate.

[0052] At block 320, prior to deposition of a contact metal layer on the substrate 402, but after the substrate 402 is provided in the metal deposition processing chamber 150 at block 310, a pretreatment process may be performed to pre-treat the substrate surface 411, thus, forming a treated surface region 410 on the surface 411, sidewalls 412 and bottoms 414 of the openings 406 in the silicon containing layer 404, as shown in FIG. 4B. In certain embodiments, the substrate surface 411 may have some weak or residual dangling bonding structures of Si—F, N—F, H—F, and Si—N on the substrate surface left from the optional pre-cleaning process previously performed on the substrate 402. The dangling bonds may undesirably and adversely obstruct absorption or adherence of metallic atoms deposited on the substrate surface in the subsequent contact metal deposition process. Thus, the pretreatment process at block 320 may be performed to efficiently alter the surface bonding structure of the surface 411 of the silicon containing layer 404, thereby providing a surface having a good absorption ability to promote adherence of metallic atoms provided from the subsequent contact metal deposition process. It is believed that the pretreatment process may efficiently convert or remove the bonding structure of Si—F, H—F, N—F, and Si—N, into the bonding of Si—H or Si—Si, which may assist in the adherence of the metallic atoms to form a layer thereon.

[0053] In one embodiment, a pre-treatment gas mixture may be supplied into the metal deposition processing chamber 150 to alter the surface properties of the substrate 402 prior to the contact metal deposition process. In one embodiment, the pre-treatment gas mixture may include at least a hydrogen containing gas, such as H₂, H₂O, H₂O₂, or the like. An inert gas, such as Ar, He, Kr, and the like, may also be supplied into the pre-treatment gas mixture. Additionally, a nitrogen containing gas, such as N₂, NH₃, N₂O, NO₂, and the like, may also be supplied into the pre-treatment gas mixture. In an exemplary embodiment, the pre-treatment gas mixture supplied to pre-treat the substrate surface 411 includes a hydrogen containing gas, such as a H₂ gas, and an inert gas, such as Ar gas. In another exemplary embodiment, the pre-treatment gas mixture supplied to pre-treat the substrate surface 411 includes a hydrogen containing gas, such as a H₂ gas, an inert gas, such as Ar gas, and a nitrogen containing gas, such as a NH₃ gas.

[0054] The pre-treatment gas mixture may be supplied from a remote plasma source, such as the remote plasma source 141 coupled to the metal deposition processing chamber 150, to supply the pre-treatment gas mixture plasma remotely from the processing chamber 150 to the substrate surface 411. Alternatively, the pre-treatment gas mixture may be supplied from any other suitable sources installed in the processing chamber 150 to the substrate surface 411.

[0055] During the pretreatment process at block 320, several process parameters may be regulated to control the pretreatment process. In one exemplary embodiment, a process pressure in the metal deposition processing chamber 150 is regulated between about 50 mTorr to about 5000 mTorr, such as between about 500 mTorr and about 1000 mTorr, for example, at about 700 mTorr. An RF source power may be applied to maintain a plasma in the pretreatment gas mixture. For example, a power of about 1000 Watts to about 6000 Watts may be applied to maintain a plasma inside the processing chamber 150. The hydrogen containing gas supplied in the pretreatment gas mixture may be flowed into the processing chamber 150 at a rate between about 400 sccm to about 4000 sccm and the inert gas supplied in the pretreatment gas mixture may be flowed at a rate between about 200 sccm and about 2000 sccm. The nitrogen containing gas supplied in the pretreatment gas mixture may be flowed at a rate between about 100 sccm and about 3000 sccm. A temperature of the substrate 402 is maintained between about 125 degrees Celsius to about 250 degrees Celsius. In one embodiment, the substrate 402 is subjected to the pretreatment process for between about 10 seconds to about 2 minutes, depending on the operating temperature, pressure, and flow rate of the gas. For example, the substrate 402 can be exposed for about 30 seconds to about 60 seconds. In an exemplary embodiment, the substrate is exposed for about 40 seconds or less.

[0056] Optionally, at block 330 a barrier layer deposition process may be performed to deposit a barrier layer 416 on the substrate, as shown in FIG. 4C. The barrier layer 416 generally prevents diffusion of the contact metal layer to the junction material on the substrate, typically a silicon or silicon germanium compound. The barrier layer generally contains a metal or a metal nitride material, such as titanium (Ti), titanium nitride (TiN), alloys thereof, or combinations thereof. The barrier layer 416 may also comprise plasma nitrided (N₂ or NH₃) Ti and PVD Cobalt. If the barrier layer 416 comprises a nitrided Ti layer, only the top few angstroms of titanium are converted to a TiN compound. It has been found that both oxidized and non-oxidized Ti and TiN barrier layers provide for improved diffusion resistance. The barrier layer 416 may have a thickness within a range from about 2 Å to about 100 Å, more narrowly within a range from about 3 Å to about 80 Å, more narrowly within a range from about 4 Å to about 50 Å, more narrowly within a range from about 5 Å to about 25 Å, more narrowly within a range from about 5 Å to about 20 Å, more narrowly within a range from about 5 Å to about 15 Å, and more narrowly within a range from about 5 Å to about 10 Å. The barrier layer is generally deposited by atomic layer deposition (ALD), plasma-enhanced ALD (PE-ALD), chemical vapor deposition (CVD), or physical vapor deposition (PVD) processes.

[0057] The barrier layer 416 is similar to a wetting layer which is described in detail below. The barrier layer 416, as described above, generally prevents diffusion of the contact metal layer to the junction material on the substrate. A wetting layer generally enhances the adherence of the contact metal layer, Cobalt in some embodiments, which reduces the formation of undesirable voids in the features during annealing processes performed on the contact metal layer.

[0058] At block 340, after the pre-treatment process of block 320 is performed on the substrate surface to form the treated surface region 410 or deposition of the barrier layer 416 in block 330, a CVD contact metal deposition process may be performed in the processing chamber 150 to deposit a contact metal layer 420, as shown in FIG. 4D. The contact metal layer 420 may be deposited using the cyclic deposition process described in FIG. 5. The contact metal layer 420 fills the opening 406. Suitable examples of the contact metal layer 420 include titanium (Ti), cobalt (Co), nickel (Ni), alloys thereof, or any combination thereof. In one particular embodiment described therein, the contact metal layer 420 deposited on the substrate 402 is a cobalt (Co) layer.

[0059] The contact metal layer 420 may be deposited using a multi-step deposition process comprising multiple cycles of performing a cyclic metal deposition process to deposit the contact metal layer 420 followed by annealing the contact metal layer 420. In certain embodiments, the thickness of the contact metal layer 420 should be less than 50% of the feature diameter (critical dimension) of the smallest feature to be filled. For example, the cyclic metal deposition process is performed to partially fill a feature to less than half of the feature diameter followed by an anneal process. The cyclic deposition process followed by an anneal would then be repeated to deposit until the contact metal layer 420 achieved a predetermined thickness. In an alternative embodiment, the contact metal layer 420 may be deposited to completely fill the feature in a single, non-cyclic deposition process. In this embodiment, the contact metal layer 420 is then annealed. The non-cyclic contact metal layer 420 deposition process and subsequent anneal processes increase throughput because they require less time to complete.

[0060] FIG. 5 depicts a flow diagram for a cyclic deposition process as shown in block 340 for forming a contact metal layer, such as contact metal layer 420, in a semiconductor device in accordance with one embodiment of the present invention. In one embodiment, process includes exposing a substrate to a deposition gas to form a portion of a contact metal layer (block 510), optionally purging the deposition chamber (block 520), exposing the substrate to a plasma treatment process (block 530), optionally purging the deposition chamber (block 540), and determining if a predetermined thickness of the cobalt contact metal layer has been achieved (block 550). In one embodiment, the cycle of blocks 510-550 may be repeated if the cobalt contact metal layer has not been formed having the predetermined thickness. Alternately, the process may be stopped once the contact metal layer has been formed having the predetermined thickness.

[0061] During the contact metal deposition process, the contact metal layer 420 may be formed or deposited by introducing a deposition precursor gas mixture including a cobalt precursor or a nickel precursor simultaneously with, sequentially with, or alternatively without a reducing gas mixture (reagent), such as a hydrogen gas (H₂) or a NH₃ gas, into the metal deposition processing chamber 150 during a thermal CVD process, a pulsed-CVD process, a PE-CVD process, a pulsed PE-CVD process, or a thermal ALD process. Additionally, the deposition precursor gas mixture may also include a purge gas mixture supplied concurrently into the processing chamber for processing. In another embodiment, the contact metal layer 420 may be formed or deposited by sequentially repetitively introducing a pulse of the deposition precursor gas mixture, such as a cobalt precursor, and a pulse of a reducing gas mixture, such as a hydrogen gas (H₂) or a NH₃ gas, into the metal deposition processing chamber 150 during a thermal ALD process or a pulsed PE-CVD process. In another embodiment, the contact metal layer 420 may be formed or deposited by continuously flowing the reducing gas mixture, such as a hydrogen gas (H₂) or a NH₃ gas, while repetitively introducing a pulse of the deposition precursor gas mixture, such as a cobalt precursor, and a pulse of a reducing gas mixture into the metal deposition processing chamber 150 during a thermal ALD process or a pulsed PE-CVD process. In another embodiment, the contact metal layer 420 may be formed or deposited by continuously flowing the reducing gas mixture, such as a hydrogen gas (H₂) or a NH₃ gas, and the deposition precursor gas mixture, such as a cobalt precursor, under plasma conditions during a PE-CVD process. In another embodiment, the contact metal layer 420 may be formed or deposited by continuously flowing the reducing gas mixture, such as a hydrogen gas (H₂) or a NH₃ gas under plasma conditions and periodically pulsing the deposition precursor gas mixture, such as a cobalt precursor during a PE-CVD process.

[0062] Suitable cobalt precursors for forming cobalt-containing materials (e.g., metallic cobalt or cobalt alloys) by CVD or ALD processes described herein include cobalt carbonyl complexes, cobalt aminidate compounds, cobaltocene compounds, cobalt dienyl complexes, cobalt nitrosyl complexes, derivatives thereof, complexes thereof, plasma thereof, or combinations thereof. In some embodiments, cobalt materials may be deposited by CVD and ALD processes further described in commonly assigned U.S. Pat. No. 7,264,846 and U.S. Ser. No. 10/443,648, filed May 22, 2003, and published as US 2005-0220998, both of which are herein incorporated by reference in their entirety.

[0063] Suitable cobalt precursors may include, but not limited to, cobalt carbonyl complexes, cobalt aminidate compounds, cobaltocene compounds, cobalt dienyl complexes, cobalt nitrosyl complexes, cobalt diazadienyl complexes, cobalt hydride complexes, derivatives thereof, complexes thereof, plasmas thereof, or combinations thereof. In one embodiment, examples of the cobalt precursors that may be used herein include dicobalt hexacarbonyl butylacetylene (CCTBA, (CO)₆Co₂(HC≡C^tBu)), dicobalt hexacarbonyl methylbutylacetylene ((CO)₆Co₂(MeC≡C^tBu)), dicobalt hexacarbonyl phenylacetylene ((CO)₆Co₂(HC≡CPh)), dicobalt hexacarbonyl methylphenylacetylene ((CO)₆Co₂(MeC≡CPh)), dicobalt hexacarbonyl methylacetylene ((CO)₆Co₂(HC≡CMe)), dicobalt hexacarbonyl dimethylacetylene ((CO)₆Co₂(MeC≡CMe)), cobalt aminidate (C₂₀H₄₂CoN), cobalt hexafluoro acetylacetone(Co(C₅HF₆O₂)₂.xH₂O), cobalt acetylacetonate ((CH₃COC═COCH₃)₃Co), cobalt (II) acetlyacteone ((CH₃COC═COCH₃)₂Co), cobalt acetate((CH₃COO)₂Co), derivatives thereof, complexes thereof, plasmas thereof, or combinations thereof. Other exemplary cobalt carbonyl complexes include cyclopentadienyl cobalt bis(carbonyl) (CpCo(CO)₂), tricarbonyl allyl cobalt ((CO)₃Co(CH₂CH═CH₂)), cobalt tricarbonyl nitrosyl (Co(CO)₃NO), derivatives thereof, complexes thereof, plasmas thereof, or combinations thereof. In one particular example of the cobalt precursors used herein is dicobalt hexacarbonyl butylacetylene (CCTBA, (CO)₆Co₂(HC≡C^tBu)). It is noted that the dicobalt hexacarbonyl butylacetylene (CCTBA, (CO)₆Co₂(HC≡C^tBu)) precursor may be supplied into the metal deposition processing chamber 150 with a carrier gas, such as a Ar gas.

[0064] Examples of the alternative reagents (i.e., reducing agents used with cobalt precursors for forming the cobalt materials during the deposition process as described herein may include hydrogen (e.g., H₂ or atomic-H), nitrogen (e.g., N₂ or atomic-N), ammonia (NH₃), hydrazine (N₂H₄), a hydrogen and ammonia mixture (H₂/NH₃), borane (BH₃), diborane (B₂H₆), triethylborane (Et₃B), silane (SiH₄), disilane (Si₂H₆), trisilane (Si₃H₈), tetrasilane (Si₄H₁₀), methyl silane (SiCH₆), dimethylsilane (SiC₂H₈), phosphine (PH₃), derivatives thereof, plasmas thereof, or combinations thereof. In one particular example, the reagents or reducing agents used herein is ammonia (NH₃).

[0065] During the cyclic deposition process at block 340, in between each pulse of the deposition precursor gas mixture and the plasma pretreatment process, a purge gas mixture may be supplied from a side/edge and/or a bottom of the processing chamber 150 in between each or selected deposition precursor pulses to the edge portion 151 of the substrate 402. The purge gas mixture may be supplied from the side and/or bottom purge gas source 123 and 125 disposed in the processing chamber 150 to supply the purge gas mixture to an edge/periphery of the substrate 402 surface. It is noted that the edge/periphery region of the substrate 402 as described herein may refer to a substrate 402 edge region between about 1 mm and about 5 mm from the substrate edge/bevel for a 300 mm substrate or between about 145 mm and about 149 mm from the substrate center point/center line (e.g. a diameter passing through the substrate center point). It should also be understood that gas flows during the plasma treatment process of block 530 may also serve to purge the process chamber.

[0066] In one embodiment, the purge gas mixture supplied in the contact metal deposition process may include at least a hydrogen containing gas and an inert gas. It is noted that the purge gas mixture may be supplied with the deposition precursor gas mixture during the deposition process as needed. Suitable examples of the hydrogen containing gas may include H₂, H₂O, H₂O₂ or the like. Suitable examples of the inert gas include Ar, He, or Kr. In one particular embodiment, the purge gas mixture supplied during the metal deposition process may include H₂ and Ar gas.

[0067] In one embodiment of the deposition process, a pulse of the deposition precursor gas mixture along with a reducing gas and optionally a purge/carrier gas mixture is supplied to the deposition chamber 150. The term pulse as used herein refers to a dose of material injected into the process chamber. The pulse of the deposition precursor gas mixture continues for a predetermined time interval. Between each pulse of the deposition precursor gas mixture and the plasma treatment process, the purge gas mixture may be pulsed into the processing chamber in between each or multiple pulses of the deposition precursor gas mixture to remove the impurities or residual precursor gas mixture which is unreacted/non-absorbed by the substrate 402 surface (e.g., unreacted carbon containing impurities from the cobalt precursor or others) so they may be pumped out of the processing chamber.

[0068] The time interval for the pulse of the deposition precursor gas mixture is variable depending on a number of factors such as, film thickness requirement, process chamber volume, throughput concern, gas flow rate, and the like. In one embodiment, the process conditions are advantageously selected so that a pulse of the deposition precursor gas mixture provides a sufficient amount of precursor, such that at least a monolayer of the cobalt metal precursor is adsorbed on the substrate 402. Thereafter, excess cobalt metal precursor remaining in the chamber may be removed from the processing chamber and pumped out by the purge gas mixture.

[0069] In some embodiments, the reducing gas mixture may be supplied concurrently with the deposition precursor gas mixture in a single pulse to form the contact metal layer 416. In one embodiment depicted herein, the pulse of the reducing gases may be co-flowed with the deposition precursor gas mixture after a first few pulses, such as between first to fifth pulses, of the deposition precursor gas mixture.

[0070] In operation at block 510, a first pulse of the deposition precursor gas mixture is pulsed into the processing chamber 150 to deposit a portion of the cobalt contact metal layer 420 on the substrate. Each pulse of the deposition precursor gas mixture into the processing chamber 150 may deposit a cobalt layer having a thickness between about 5 Å and about 100 Å. During pulsing of the deposition precursor gas mixture, several process parameters are also regulated. In one embodiment, the process pressure is controlled at between about 7 Torr and about 30 Torr. The processing temperature is between about 125 degrees Celsius and about 250 degrees Celsius. For plasma enhanced processes, the RF power may be controlled at between about 100 Watts and about 1200 Watts. The cobalt gas precursor supplied in the deposition precursor gas mixture may be controlled at between about 1 sccm and about 10 sccm. The reducing gas, such as the H₂ gas, may be supplied at between about 100 sccm and about 10,000 sccm, such as between about 3000 sccm to about 5000 sccm. The H₂ gas supplied from the substrate edge/substrate bottom may be controlled at between about 200 sccm and about 1000 sccm. Argon gas may be supplied from the substrate edge/substrate bottom at between about 200 sccm and about 1000 sccm.

[0071] Optionally, after block 510, the process chamber may be purged. After pulsing of the deposition precursor gas mixture, a purge gas mixture is then supplied into the processing chamber to purge out the residuals and impurities from the processing chamber. During pulsing of the purge gas mixture, the process pressure may be pumped down to a certain low level, such as lower than 2 Torr, for example lower than 0.5 Torr, at a relatively short time interval, such as between about 1 seconds and about 5 seconds, so as to assist rapidly pumping out the residuals and impurities from the processing chamber. Several process parameters are also regulated during pulsing of the purge gas mixture. In one embodiment, the process pressure is controlled at between about 0.1 Torr and about 2 Torr, such as 0.1 Torr and about 1 Torr, for example between about 0.1 Torr and about 0.6 Torr. The processing temperature is between about 125 degrees Celsius and about 250 degrees Celsius. The RF power may be controlled at between about 100 Watts and about 800 Watts. The H₂ gas supplied in the purge gas mixture may be controlled at between about 200 sccm and about 1000 sccm. The Ar gas may be supplied at between about 200 sccm and about 1000 sccm.

[0072] Subsequent to either exposing the substrate 402 to a deposition gas at block 510 or purging the deposition chamber at block 520 the substrate 402 is exposed to a plasma treatment process. The plasma treatment process reduces surface roughness and improves the resistivity of the as deposited portion of the cobalt contact metal layer 420. Exemplary plasma forming gases include hydrogen (H₂), nitrogen (N₂), ammonia (NH₃), and combinations thereof. During the plasma treatment process, several process parameters are also regulated. In one embodiment, the process pressure is controlled at between about 7 Torr and about 30 Torr. The processing temperature is between about 125 degrees Celsius and about 250 degrees Celsius. The RF power may be controlled at between about 100 Watts and about 800 Watts, for example, about 400 Watts. The plasma forming gas, such as H₂ gas, may be supplied at between about 3000 sccm and about 5000 sccm, for example, about 4000 sccm. The H₂ gas supplied from the substrate edge/substrate bottom may be controlled at between about 200 sccm and about 1000 sccm. The Ar gas may be supplied from the substrate edge/substrate bottom at between about 200 sccm and about 1000 sccm.

[0073] It has been shown that the plasma treatment either during deposition or after deposition helps reduce the surface roughness of the as-deposited film and helps reduce carbon impurities in the as-deposited film. Thus, H radical life time, especially inside the narrow (<15 nm critical dimension and >5 aspect ratio) via and trench structures expected for transistor technology node ≦14 nm, is an important parameter to enable seamless and void-free cobalt gap fill. The life time of the H radical inside the chamber during a CVD process can be improved by flowing an inert gas, such as He, Ne, Ar, among others, during the plasma treatment using an inductively coupled plasma source, microwave plasma source, or e-beam plasma source. The plasma sources are available from Applied Materials, Inc. or other vendors.

[0074] Subsequent to exposing the substrate to a plasma treatment process in block 530, the deposition chamber may optionally be purged in block 540. The optional purge of block 540 may be performed similarly to the purge process described in block 520.

[0075] At block 550, if the predetermined thickness of the contact metal layer 420 has not been achieved, additional cycles starting from exposing the substrate to the deposition precursor gas mixture followed with the plasma pretreatment process can then be repeatedly performed until a desired thickness range of the contact metal layer 420 is reached. If the predetermined thickness of the contact metal layer has been achieved, the process proceeds to block 350 where a thermal annealing process is performed.

[0076] For example, if the total thickness of the contact metal layer is 10 nm and the portion of the contact layer is deposited at 2 nm/cycle then 5 cycles of (2 nm deposition followed by plasma treatment) will be needed.

[0077] At block 350, a thermal annealing process is performed in a thermal annealing chamber on the substrate 402 to improve the properties of the contact metal layer 420. The thermal annealing chamber may be one of the chambers processing chamber 212, 214, 216, 232, 234, 236, 238 of the system 200 as needed. In one embodiment, the thermal annealing process performed at block 350 may have a temperature range between about 200 degrees Celsius and about 1400 degrees Celsius, such as between about 200 degrees Celsius and about 500 degrees Celsius. During the thermal annealing process, a gas mixture including at least a hydrogen containing gas and/or an inert gas (e.g., argon) is supplied into the annealing chamber. The gas mixture may be supplied to the annealing chamber using either a static process where the chamber is filled with gas prior to the anneal process or a continuous flow process where the gas mixture is continuously flowed through the annealing chamber during the anneal process.

[0078] In one embodiment, the thermal annealing process at 350 may be performed by supplying a gas mixture including at least one of a hydrogen containing gas, an inert gas, and a nitrogen containing as into the annealing chamber at a flow rate between about 100 sccm and about 2000 sccm, controlling a chamber pressure of about 0.5 Torr and about 15 Torr, for example, between about 5 Torr and about 8 Torr, maintaining a temperature range between about 150 degrees Celsius and about 500 degrees Celsius, for example, between about 300 degrees Celsius and about 475 degrees Celsius, and performing the thermal annealing process, optionally while rotating the substrate, for between about 30 seconds and about 600 seconds. Suitable examples of gases for the gas mixture supplied in the thermal annealing chamber may include a hydrogen gas, a nitrogen containing gas, an inert gas (e.g., argon) or other gases as needed. In one embodiment, the gas mixture supplied into the processing chamber to perform the silicidation process includes hydrogen gas (H₂) supplied at a flow ratio between about 1:10 and about 1:1, such as about 1:3.

[0079] An example of a suitable thermal processing chamber, in which block 350 may be performed, is a dual mode degas (DMD) chamber, available from Applied Materials, Inc. Other examples of suitable thermal processing chambers are the Vantage® Vulcan™ RTP chamber and the Vantage® Astra™ DSA chamber. It should be noted that the annealing process may not necessarily be integrated with the contact metal layer 420 deposition chamber. The use of RTP and DSA anneal may provide for further control of temperature uniformity and rapid temperature change. It is noted that other thermal annealing chamber available from other manufactures may also be utilized to practice the present invention.

[0080] After the thermal annealing process is completed, at block 360, if the predetermined thickness of the contact metal layer 420 has not been achieved, additional cycles starting from performing a cyclic metal deposition to deposit a contact metal layer at block 340 followed by performing an annealing process on the contact metal layer at block 350 can then be repeatedly performed until a desired thickness range of the contact metal layer 420 is reached. If the predetermined thickness of the contact metal layer has been achieved, the process is complete and additional processing steps may be performed.

[0081] Thus, according to the aforementioned embodiments, methods for depositing a contact metal layer in a contact structure are provided. The methods include filling contact holes with seamless contact metal layers by annealing the as-deposited contact metal layers. Annealing of CVD cobalt films results in a bottom-up, seamless gap fill. In certain embodiments, a wetting layer is not required for reflow of cobalt. Thickness of the contact metal layer (e.g., CVD cobalt layer) may be less than 50% of the feature diameter (critical dimension). A cyclic process utilizing a combination of thin cobalt film deposition and short-time anneal is used. Ambience during the short-time anneal lowers the required anneal temperature to achieve seamless cobalt fill. A blanket wafer study demonstrates 50% reduction in resistivity of cobalt films after the anneal treatment. Variations of anneal time, temperature, atmosphere (type of gas used), static gas pressure or gas flow during the anneal step may be used to reduce roughness and improve the resistivity of the contact metal layer. Short anneal time (e.g., 1 minute) is sufficient to reduce cobalt resistivity and roughness. Gas flow during anneal further improves the resistivity of cobalt films. Argon and hydrogen gas or a combination of both may be used for anneal atmosphere. PVD cobalt can be utilized in place of CVD cobalt. A combination of CVD & PVD can also be utilized where CVD cobalt acts as a wetting layer for PVD cobalt re-flow.

[0082] FIG. 6 depicts a flow diagram for forming a contact metal layer in a semiconductor device in accordance with one embodiment of the present invention. The sequence described in FIG. 6 corresponds to the fabrication stages depicted in FIGS. 7A-7E, which are discussed below. FIGS. 7A-7E illustrate schematic cross-sectional views of a substrate 402 having a device structure 408 formed thereon during different stages of fabricating a contact metal layer 420 on the device structure 408 illustrated by the processing sequence 600. The sequence of FIG. 6 is generally provided with reference to a CVD, ALD, or PVD deposited cobalt contact metal layer.

[0083] Certain aspects of process 600 are similar to process 300 described with reference to FIG. 3 and will not be repeated hereinafter for the sake of brevity. In one embodiment, blocks 610 and 620 are similar to blocks 310 and 320 depicted in FIG. 3 as described above. Blocks 610 and 620 correspond to the fabrication stages depicted in FIGS. 7A and 7B, respectively. A detailed discussion of FIGS. 7A and 7B may be found with reference to FIGS. 4A and 4B. However, performing a pretreatment process on the substrate may be optional in block 620.

[0084] Block 630 provides for performing a barrier layer deposition to deposit a barrier layer 416 on the substrate 402, as shown in FIG. 7C. The barrier layer generally contains a metal or a metal nitride material, such as titanium (Ti), titanium nitride (TiN), alloys thereof, or combinations thereof. The barrier layer 416 may also comprise plasma nitrided (N₂ or NH₃) Ti and PVD Cobalt. If the barrier layer 416 comprises a nitrided Ti layer, only the top few angstroms of titanium are converted to a TiN compound. It has been found that non-oxidized Ti and TiN barrier layers provide for improved diffusion resistance. The barrier layer 416 may have a thickness within a range from about 2 Å to about 100 Å, more narrowly within a range from about 3 Å to about 80 Å, more narrowly within a range from about 4 Å to about 50 Å, more narrowly within a range from about 5 Å to about 25 Å, more narrowly within a range from about 5 Å to about 20 Å, more narrowly within a range from about 5 Å to about 15 Å, and more narrowly within a range from about 5 Å to about 10 Å. The barrier layer is generally deposited by atomic layer deposition (ALD), plasma-enhanced ALD (PE-ALD), chemical vapor deposition (CVD), or physical vapor deposition (PVD) processes.

[0085] In one embodiment, performing a barrier layer deposition comprises an ALD process comprising providing a Ti containing precursor which may be provided to the chamber in the presence of a carrier gas, such as an inert gas. In another embodiment, a Ti containing precursor may be provided with a nitrogen containing precursor to form a barrier layer comprising TiN. The Ti containing precursor and the nitrogen containing precursor may be provided in the presence of a carrier gas, such as an inert gas. In another embodiment, a nitridation process may be performed on a deposited Ti layer to form a TiN barrier layer. In another embodiment, the Ti barrier layer is deposited by a PVD Ti process.

[0086] Block 635 provides for performing a wetting layer deposition to deposit a wetting layer 718 on the substrate 402, as shown in FIG. 7D. The wetting layer 718 is deposited over the barrier layer 416. The wetting layer is generally deposited by a process selected from PVD Co, CVD TiN, PVD TiN, CVD Ru, PVD Ru, nitridation of PVD Ti, or combinations thereof. In embodiments using a CVD process to deposit the wetting layer 718, a desired precursor gas is provided to the chamber and may be further provided in the presence of a carrier gas. In embodiments using a PVD process to deposit the wetting layer 718, a target comprising the desirable material to be deposited is provided and a PVD process is performed to deposit a PVD wetting layer. In one embodiment, the wetting layer comprises PVD TiN. In this embodiment, a Ti target is provided and bombarded with ions to sputter Ti to deposit the wetting layer 718 over the barrier layer 416. A nitridation process using a nitrogen containing precursor, such as NH₃, in the presence of a plasma is performed on the PVD Ti layer to form the TiN wetting layer 718. In this embodiment, the wetting layer 718 comprises a nitrided Ti layer and only the top few angstroms of titanium are converted to a TiN compound. In another embodiment, the wetting layer is PVD Co. In this embodiment, a Co target is provided and bombarded with ion to sputter co to deposit the wetting layer 718 over the barrier layer 416. In the embodiment using PVD Co, RF power is provided at a frequency from about 5000 W to about 6000 W, such as about 5500 W. A power of the PVD Co process is provided from about 400 W to about 600 W, such as about 500 W and the pressure of the chamber while performing the PVDCo process is from about 50 mT to about 150 mT, such as about 100 mT.

[0087] It should be known that a wetting layer of Ti or TiN may be deposited in the same chamber (under high vacuum) as a subsequent CVD Co deposition process. In an alternate embodiment, agglomeration of CVD Co films during anneal involved using CVD Co (with different film properties) as a wetting layer. This CVD Co wetting layer included high carbon atomic %>5% carbon compared to <1% carbon for CVD Co films used for gap-fill purpose. The high carbon content CVD Co films were obtained using lower H2 partial pressure during deposition step and by eliminating cyclic H2 plasma treatment.

[0088] It should be noted that any of the aforementioned wetting layer 718 processes may be performed with the subsequent contact metal layer deposition process which is provided at block 640. The wetting layer 718 and the barrier layer 416 generally enhance the subsequent contact metal layer deposition. It has been found that voids may form at the bottom of a feature on the substrate or at other locations in the feature. The voids are believed to be formed as a result of agglomeration, or the accumulation of the contact metal layer, when the contact metal layer is annealed. The voids are generally undesirable because a void between the substrate and the contact metal layer ultimately reduces the quality of the contact and negatively affects overall device performance. Further, inter-diffusion between the contact metal layer and the underlying substrate during anneal processes result in Co and silicon inter-diffusion. The inter-diffusion negatively affects device performance and leads to unpredictable device behavior. The barrier layer 416, either alone or in combination with the wetting layer 718, reduces the Co and silicon inter-diffusion. Further, the wetting layer, either alone or in combination with the barrier layer 416, enhances the adhesion of the contact metal layer when it is deposited to fill the vias and trenches of the device by reducing the probability of agglomeration during subsequent anneal processes.

[0089] In an alternate embodiment, agglomeration of CVD Co films during an anneal process may use CVD Co as a wetting layer. This CVD Co wetting layer may include a high carbon content (atomic %>5%) carbon as compared to a low carbon content (atomic %<1%) carbon for CVD Co films used for seamless gap-fill. The high carbon content CVD Co films were obtained using lower H2 partial pressure during the deposition step and by eliminating cyclic H2 plasma treatment.

[0090] Block 640 provides performing a cyclic metal deposition to deposit a contact metal layer on the substrate. The process parameters and description of the cyclic metal deposition process may be found above with regard to block 340 in FIG. 3 and the corresponding description related to FIG. 5. Block 650 provides for performing an annealing process on the contact metal layer disposed on the substrate. The process parameters and description of the performing an annealing process may be had with reference to block 350 in FIG. 3.

[0091] After the thermal annealing process is completed, at block 660, if the predetermined thickness of the contact metal layer 420 has not been achieved, additional cycles starting from performing a cyclic metal deposition to deposit a contact metal layer at block 640 followed by performing an annealing process on the contact metal layer at block 650 can then be repeatedly performed until a desired thickness range of the contact metal layer 420 is reached. If the predetermined thickness of the contact metal layer has been achieved, the process is complete and additional processing steps may be performed.

[0092] As noted above, process sequence 600 described in FIG. 6, may be had with reference to CVD, ALD, or PVD contact metal deposition processes. An integrated (non-oxidized) CVD or ALD TiN barrier layer 418 reduced the presence of voids at the bottom of the device feature. A vacuum break may be introduced after the wetting layer 718 deposition or after the contact metal layer 420 deposition before performing the anneal process of block 650. It should be noted that the anneal process of block 650 may be performed in a chamber other than the chamber in which the contact metal layer 420 was deposited. Moreover, it was found that a high frequency of H₂ plasma treatment (plasma treatment at a CVD Co thickness of 20 Å or less), as provided at block 640 (See FIG. 5 for related plasma processing parameters), played a significant role in eliminating void formation at the bottom of the device features. Finally, it has been found that the reflow characteristics of CVD or ALD contact metal layers may be regulated by controlling the atomic percent of impurities (i.e. carbon, oxygen, nitrogen, etc.) by the aforementioned process variables provided in process sequence 600. A one percent or lower carbon impurity level may be necessary for enabling a seamless contact metal layer gap-fill, more specifically, a seamless cobalt gap-fill. In addition to the process variables of the contact metal layer deposition, the impurity levels may be further controlled by the barrier layer 418 and the wetting layer 718.

[0093] FIG. 8 depicts a flow diagram for forming a contact metal layer in a semiconductor device in accordance with one embodiment of the present invention. The sequence described in FIG. 8 corresponds to the fabrication stages depicted in FIGS. 7A-7E, which are discussed below. FIGS. 7A-7E illustrate schematic cross-sectional views of a substrate 402 having a device structure 408 formed thereon during different stages of fabricating a contact metal layer 420 on the device structure 408 illustrated by the processing sequence 800. The sequence of FIG. 8 is generally provided with reference to a PVD deposited cobalt contact metal layer.

[0094] Processing sequence 800 begins by providing a substrate at block 810. A detailed description of block 810 may be had by reference to the descriptions related to blocks 310 in FIG. 3 and block 610 in FIG. 6. Block 820 provides for optionally performing a pretreatment process on the substrate. Detailed description related to block 820 may be had by reference to the descriptions related to block 320 in FIG. 3 and block 620 in FIG. 6.

[0095] Block 830 provides performing a barrier layer deposition to deposit a barrier layer on the substrate. A general description regarding the barrier layer 416 may be had with reference to block 630 in FIG. 6. In one embodiment, a TiN barrier layer, such as the TiN barrier layer 416 described above, is disposed on the substrate. In this embodiment, the TiN layer is provided at a thickness of between about 5 Å and about 75 Å, such as about 50 Å. However, it has been shown that a 10 Å TiN layer may be sufficient as a barrier layer. The TiN barrier layer 416 is formed by NH₃ or N₂ nitridation of a previously deposited Ti layer or by a CVD deposition process. Processing parameters for the deposition of the TiN barrier layer 416 may be found with regard to block 630 in FIG. 6.

[0096] Block 835 provides performing a wetting layer deposition to deposit a wetting layer on the substrate. A general description of the wetting layer 718 may be had with reference to block 635 in FIG. 6. In one embodiment, the wetting layer 718 is deposited by a CVD or ALD process. Suitable processes for providing the wetting layer 718 include CVD TiN, CVD Co, CVD Ru, ALD TaN, and combinations thereof. In one embodiment, the wetting layer may be deposited by a CVD Co process. The cobalt deposited during the CVD process is provided to the processing chamber by a cobalt containing precursor, such as the cobalt containing precursors discussed with reference to the cyclic metal deposition process provided in FIG. 3. In one embodiment, the cobalt containing precursor is provided to the chamber in a thermal deposition process. The thermal deposition process generally comprises heating the substrate 402 to promote deposition of the cobalt on the surface of the substrate 402. In one embodiment, the thermal deposition process provides for heating the substrate from about 100° C. to about 200° C., such as about 150° C. In this embodiment, the cobalt deposited during the CVD Co process is the wetting layer 718 which is disposed over the barrier layer 416.

[0097] Block 840 provides for performing an annealing process on the wetting layer 718. The annealing process is generally performed to reduce the surface roughness of the wetting layer 718, increase grain size of the crystalline structure, and reduce impurities, such as carbon, that may be present in the wetting layer 718. The annealing process is performed at a temperature of between about 200° C. to about 500° C., such as about 400° C. The annealing process may be performed in a chamber environment where an inert gas, such as argon, is provided in the chamber. In one embodiment, argon gas is static within the chamber and the chamber may be optionally purged after the annealing of the wetting layer 718 is performed. In one embodiment, the annealing process is performed for a duration of between about 10 seconds to about 1000 seconds, such as between about 30 seconds and about 90 seconds, such as about 60 seconds. In another embodiment, the annealing process may be performed in a chamber environment where H₂ gas is provided to the chamber in a static or flowing manner. In this embodiment, the annealing process may be performed for a duration of between about 10 seconds to about 1000 seconds.

[0098] Block 850 provides for performing a metal deposition process for depositing a contact metal layer 420 on a substrate. In one embodiment, the contact metal layer 420 is deposited by a PVD Co process. The PVD Co process may further be a thermal PVD Co process. The cobalt is sputtered using conventional processes, and in one embodiment, the sputtering process is performed in the presence of a process gas, such as argon or H₂. In one embodiment, the PVD Co process may be performed by providing RF power at a frequency from about 5000 W to about 6000 W, such as about 5500 W. The RF may be provided in a direct current at a power of between about 250 W and about 750 W, such as about 500 W. The pressure of the chamber during the PVD Co process may be maintained at a pressure of between about 50 mTorr and about 200 mTorr, such as about 100 mTorr. Once the cobalt has been sputtered to the substrate, the cobalt may be reflowed by providing heat to the substrate to reflow the as deposited cobalt. In one embodiment, the PVD Co reflow may be performed by heating the substrate to a temperature of between about 200° C. to about 500° C. In embodiments where a PVD Co process is employed, both the contact metal layer 420 deposition and anneal may be performed in the same chamber if the chamber has the capability to heat the substrate to temperatures required for processing.

[0099] Block 860 provides for exposing the contact metal layer 420 to a plasma treatment process. The plasma treatment process generally comprises providing a process gas, such as H₂, to the chamber and applying an RF current to form the process gas into a plasma. In one embodiment, the frequency of the RF current is provided between about 200 W and about 800 W, such as about 400 W. The plasma treatment process is performed for about 1 second to about 60 seconds, such as about 30 seconds. In one embodiment, the substrate 402 may be heated to a temperature of between about 100° C. to about 200° C., such as about 150° C. to further reduce the surface roughness of the contact metal layer 420 and reduce the percentage of impurities that may be present in the contact metal layer 420.

[0100] Block 870 provides for performing an annealing process on the contact metal layer 420 disposed on the substrate 402. The annealing process is generally performed to reduce the surface roughness of the contact metal layer 420 and reduce impurities, such as carbon, that may be present in the contact metal layer 420. Further the annealing process increases crystalline grain size which results in lower resistivity, resulting in improved integrated circuit performance. The annealing process is performed at a temperature of between about 200° C. to about 500° C., such as about 400° C. The annealing process is further performed in a chamber environment where an inert gas, such as argon, and a process gas, such as H₂, are provided in the chamber. In one embodiment, argon and H₂ gas are flowing within the chamber and the chamber may be optionally purged after the annealing of the contact metal layer 420 is performed. In one embodiment, the annealing process is performed between about 30 seconds and about 90 seconds, such as about 60 seconds.

[0101] In the embodiments above, the PVD Co process may be performed without a cyclic metal deposition process if the Co deposition and anneal process are performed in a chamber that provides for heating the substrate to. In an alternative embodiment, a PVD Co layer may be deposited at the bottom of a feature and may be etched and re-sputtered on the feature side wall to provide a continuous cobalt film on the side wall which allows for reflow of the PVD Co from the field to the bottom of the feature. The contact metal layer 420 deposition is performed to obtain a sufficient film thickness required for a subsequent chemical mechanical polish of the contact metal layer 420.

[0102] In another embodiment, the contact metal layer 420 deposited after a CVD Co wetting layer 718 may comprise tungsten (W). This embodiment is generally used with a dual damascene type structure having a lower part of the feature exhibiting a small critical dimension and aggressive aspect ratio. The upper portion of the dual damascene type structure generally has a greater critical dimension and less aggressive aspect ratio when compared to the lower portion. In this embodiment, the lower portion, which presents additional contact metal layer deposition challenges, may be filled with a CVD Co process as described above. The CVD Co process fills the lower portion of the feature. Following the CVD Co deposition, a CVD W process may be performed to fill the remaining portion of the feature. The CVD W process generally deposits material at a faster rate than the CVD Co process, thus allowing for increased throughput.

[0103] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.