Electrolyte with good planarization capability, high removal rate and smooth surface finish for electrochemically controlled copper CMP

[0001] This application is a Continuation in Part application of U.S. patent application Ser. No. 10/032,275, filed Dec. 21, 2001, entitled Electrolyte Composition and Treatment for Electrolytic Chemical Mechanical Polishing, which is herein incorporated by reference.

[0002] 1. Field of the Invention

[0003] Embodiments of the present invention relate to electrochemical mechanical polishing. More particularly, embodiments of the present invention relate to an electrolyte solution for copper removal and a method for removing copper from a substrate.

[0004] 2. Background of the Related Art

[0005] 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 circuit technology are pushed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on processing capabilities. Reliable formation of interconnects is important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates and die.

[0006] Multilevel interconnects are formed using sequential material deposition and material removal techniques on a substrate surface to form features therein. As layers of materials are sequentially deposited and removed, the uppermost surface of the substrate may become non-planar across its surface and require planarization prior to further processing. Planarization or polishing is a process where material is removed from the surface of the substrate to form a generally even, planar surface. Planarization is useful in removing excess deposited material and removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials to provide an even surface for subsequent lithography and processing.

[0007] Electrochemical mechanical polishing (ECMP) is one method of planarizing a surface of a substrate. ECMP removes conductive materials from a substrate surface by electrochemical dissolution while polishing the substrate with a reduced mechanical abrasion compared to conventional chemical mechanical planarization (CMP) processes, which may require a high relative down force on a substrate to remove materials, such as copper, from the substrate. A typical ECMP system includes a substrate support and two electrodes disposed within an electrolyte containment basin. In operation, metal atoms on a surface of a substrate are ionized by an electrical current from a source of potential, such as a battery or other voltage source connected to the two electrodes. The metal ions dissolve into the surrounding electrolyte solution at a rate proportional to the electric current. The metal ions from the substrate (anode) either plate the electrode (cathode), fall out of the solution as a precipitate of complexes, or remain in the solution. The destiny of the metal ions depends greatly on the chemistry of the metals and the solution.

[0008] While ECMP typically subjects a substrate to a lower down force than CMP, ECMP processing conditions, such as the pressure and the length of processing, may result in damage to the substrate surface. In particular, substrates containing low dielectric constant (low k) dielectric materials, such as carbon doped silicon oxides or other porous low k materials, may be deformed or scratched under ECMP processing conditions.

[0009] Therefore, there is a need for compositions and methods for planarizing a substrate with an electrolyte composition that minimizes damage to the substrate during planarization.

[0010] Embodiments of the present invention generally provide electrolyte compositions and methods for using electrolyte compositions to planarize substrate surfaces. In one embodiment, the electrolyte composition includes one or more chelating agents, one or more corrosion inhibitors, and one or more pH adjusting agents.

[0011] In another embodiment, the electrolyte composition includes one or more chelating agents, two or more corrosion inhibitors comprising an organic compound having azole groups and a polymeric inhibitor, and one or more pH adjusting agents.

[0012] In a further embodiment, the electrolyte composition includes one or more chelating agents, one or more corrosion inhibitors comprising one or more polymeric inhibitors, one or more pH adjusting agents, and one or more electrically resistive additives.

[0013] Methods for planarizing a surface of a substrate include polishing the substrate with any of the electrolyte compositions described herein.

[0014] So that the manner in which the above recited aspects of the present invention are attained and can be understood in detail, a more particular description of embodiments of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings.

[0015] It is to be noted, however, that the appended drawings illustrate only typical 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.

[0016] FIG. 1 is a partial section view of a polishing process station.

[0017] The words and phrases used herein should be given their ordinary and customary meaning in the art by one skilled in the art unless otherwise further defined. Chemical polishing should be broadly construed and includes, but is not limited to, planarizing a substrate surface using chemical activity. Electropolishing should be broadly construed and includes, but is not limited to, planarizing a substrate by the application of electrochemical activity. Electrochemical mechanical polishing (ECMP) should be broadly construed and includes, but is not limited to, planarizing a substrate by the application of electrochemical activity, mechanical activity, or a combination of both electrochemical and mechanical activity to remove material from a substrate surface. Anodic dissolution should be broadly construed and includes, but is not limited to, the application of an anodic bias to a substrate directly or indirectly which results in the removal of conductive material from a substrate surface and into a surrounding electrolyte composition. Percentages of electrolyte components in electrolyte compositions by volume or weight refer to percentages based on volume for liquid composition components and percentages based on weight for solid composition components.

[0018] In one aspect, electrolyte compositions that can planarize metals, such as copper, are provided. Although the electrolyte compositions are particularly useful for removing copper, it is believed that the electrolyte compositions also may be used for the removal of other conductive materials, such as aluminum, platinum, tungsten, titanium, gold, and silver.

[0019] In one embodiment, the electrolyte composition comprises one or more chelating agents, one or more corrosion inhibitors, and one or more pH adjusting agents. It is believed that the electrolyte compositions described herein contribute to a high removal rate of material, such as copper, during ECMP, good planarization of substrates, and smooth surfaces of substrates after polishing.

[0020] In any of the embodiments described herein, the chelating agents can bind to materials to be removed from the surface of a substrate, such as copper. The one or more chelating agents can include one or more groups selected from the group consisting of amine groups, amide groups, carboxylate groups, dicarboxylate groups, tri-carboxylate groups, and combinations thereof. The one or more chelating agents may include ethylenediamine, hexadiamine, amino acids, ammonium oxalate, ammonium citrate, ammonium succinate, citric acid, monobasic potassium citrate, dibasic potassium citrate, tribasic potassium citrate, tartaric acid, potassium tartarate, ammonium tartarate, succinic acid, potassium succinate, oxalic acid, potassium oxalate, and combinations thereof. The electrolyte composition may include between about 0.1% and about 15% by volume or weight of the one or more chelating agents.

[0021] In any of the embodiments described herein, the corrosion inhibitors can prevent the oxidation or corrosion of metal surfaces by forming a layer of material to reduce or minimize chemical interaction between material deposited on a substrate surface and the surrounding electrolyte. The layer of material formed by the corrosion inhibitors insulates the surface from the surrounding electrolyte, and thus, suppresses or minimizes the current on the substrate surface and limits electrochemical deposition and/or dissolution. The one or more corrosion inhibitors can include an organic compound having azole groups. Examples of organic compounds having azole groups include benzotriazole, mercaptobenzotriazole, and 5-methyl-1-benzotriazole. The electrolyte composition may include between about 0.01% and about 1.0% by volume or weight of the organic compound having azole groups.

[0022] The one or more pH adjusting agents contribute to the pH adjustment of the electrolyte composition. The preferred pH of the electrolyte composition is typically between about 3 and about 10. pH adjusting agents that can be used include acetic acid, citric acid, oxalic acid, phosphate-containing components, or combinations thereof. Phosphate-containing components that can be used include phosphoric acid, ammonium phosphates, potassium phosphates, or combinations thereof. The electrolyte composition may include between about 0.2% and about 25% by volume or weight of the one or more pH adjusting agents.

[0023] The one or more pH adjusting agents may also include a base, such as potassium hydroxide or ammonium hydroxide. The amount of base used in the electrolyte composition is typically the amount required to adjust the pH of the composition to the desired level. For example, the composition may include between about 0.1% and about 10% by volume of a base, such as potassium hydroxide or ammonium hydroxide.

[0024] The electrolyte composition may include a base and a compound selected from the group consisting of acetic acid, citric acid, oxalic acid, phosphoric acid, ammonium phosphates, potassium phosphates, or combinations thereof. In compositions which include both a base and a compound selected from the group consisting of acetic acid, citric acid, oxalic acid, phosphoric acid, ammonium phosphates, potassium phosphates, or combinations thereof, the composition may comprise between about 0.1% and about 10% by volume of the base, and between about 0.2% and about 25% by volume or weight of the compound selected from the group consisting of acetic acid, citric acid, oxalic acid, phosphoric acid, ammonium phosphates, potassium phosphates, or combinations thereof.

[0025] The balance or remainder of the electrolyte compositions described above typically is or includes deionized water.

[0026] An example of an electrolyte composition that includes one or more chelating agents, one or more corrosion inhibitors, and one or more pH adjusting agents is an electrolyte composition that includes about 2% by volume ethylenediamine, about 2% by weight ammonium citrate, about 0.2% by weight benzotriazole, and about 6% by volume phosphoric acid. The pH of the composition is about 6, which may be achieved by, for example, the composition further including potassium hydroxide to adjust the pH to the preferred range. The remainder of the electrolyte composition is deionized water.

[0027] In another embodiment, an electrolyte composition comprises one or more chelating agents, two or more corrosion inhibitors comprising an organic compound having azole groups and a polymeric inhibitor, and one or more pH adjusting agents. It is believed that the electrolyte compositions described herein contribute to a high removal rate of material, such as copper, during ECMP, good planarization of substrates, and smooth surfaces of substrates after polishing. It is believed that the compositions described herein have a low viscosity, and thus reduce the amount of friction to which a substrate is exposed during ECMP. Highly viscous electrolyte compositions can increase the friction to a substrate during ECMP, and thus increase the potential for damage to the substrate.

[0028] The one or more chelating agents can include one or more groups selected from the group consisting of amine groups, amide groups, carboxylate groups, dicarboxylate groups, tri-carboxylate groups, and combinations thereof. The one or more chelating agents may include ethylenediamine, hexadiamine, amino acids, ammonium oxalate, ammonium citrate, ammonium succinate, citric acid, monobasic potassium citrate, dibasic potassium citrate, tribasic potassium citrate, tartaric acid, potassium tartarate, ammonium tartarate, succinic acid, potassium succinate, oxalic acid, potassium oxalate, and combinations thereof. The electrolyte composition may include between about 0.1% and about 15% by volume or weight of the one or more chelating agents.

[0029] The organic compound having azole groups can be selected from the group consisting of benzotriazole, mercaptobenzotriazole, and 5-methyl-1-benzotriazole. Polymeric inhibitors that may be used include polyalkylaryl ether phosphate, ammonium nonylphenol ethoxylate sulfate, polyammonium nonylphenol ethoxylate sulfate, sulfates of nonylphenol ethoxylate, phosphates of nonylphenol ethoxylate, potassium derivatives of nonylphenol ethoxylate sulfate, phosphate derivatives of alkylphenol ethoxylate, sulfate derivatives of alkylphenol ethoxylate, phosphate derivatives of alkylether, sulfate derivatives of alkylether, phosphate derivatives of alkyl alkanol amide, sulfate derivatives of alkyl alkanol amide, polyalkoxylated amide, and combinations thereof. The electrolyte composition may include between about 0.01% and about 1.0% by volume or weight of the organic compound having azole groups and between about 0.002% and about 1.0% by volume or weight of the polymeric inhibitor. It is believed that using the combination of the organic compounds having azole groups and the polymeric inhibitors rather than only a higher concentration of an organic compound having azole groups results in the formation of a softer layer of material that is more easily removed from a substrate surface. Therefore, it is believed that the substrate is less likely to be damaged if such a combination of corrosion inhibitors is used.

[0030] The one or more pH adjusting agents contribute to the pH adjustment of the electrolyte composition. The preferred pH of the electrolyte composition is typically between about 3 and about 10. pH adjusting agents that can be used include acetic acid, citric acid, oxalic acid, phosphate-containing components, or combinations thereof. Phosphate-containing components that can be used include phosphoric acid, ammonium phosphates, potassium phosphates, or combinations thereof. The electrolyte composition may include between about 0.2% and about 25% by volume or weight of the one or more pH adjusting agents.

[0031] The one or more pH adjusting agents may also include a base, such as potassium hydroxide or ammonium hydroxide. The amount of base used in the electrolyte composition is typically the amount required to adjust the pH of the composition to the desired level. For example, the composition may include between about 0.1% and about 10% by volume of a base, such as potassium hydroxide or ammonium hydroxide.

[0032] The electrolyte composition may include a base and a compound selected from the group consisting of acetic acid, citric acid, oxalic acid, phosphoric acid, ammonium phosphates, potassium phosphates, or combinations thereof. In compositions which include both a base and a compound selected from the group consisting of acetic acid, citric acid, oxalic acid, phosphoric acid, ammonium phosphates, potassium phosphates, or combinations thereof, the composition may comprise between about 0.1% and about 10% by volume of the base, and between about 0.2% and about 25% by volume or weight of the compound selected from the group consisting of acetic acid, citric acid, oxalic acid, phosphoric acid, ammonium phosphates, potassium phosphates, or combinations thereof.

[0033] The balance or remainder of the electrolyte compositions described above typically is or includes deionized water.

[0034] An example of an electrolyte composition that includes one or more chelating agents, two or more corrosion inhibitors comprising an organic compound having azole groups and a polymeric inhibitor, and one or more pH adjusting agents is an electrolyte composition that includes about 2% by volume ethylenediamine, about 4% by weight ammonium citrate, about 0.04% by weight benzotriazole, about 6% by volume phosphoric acid, and about 0.3% by volume ammonium nonylphenol ethoxylate sulfate. The pH of the composition is about 6, which may be achieved by, for example, the composition further including potassium hydroxide to adjust the pH to the preferred range. The remainder of the electrolyte composition is deionized water.

[0035] In another embodiment, an electrolyte composition comprises one or more chelating agents, one or more corrosion inhibitors comprising one or more polymeric inhibitors, one or more pH adjusting agents, and one or more electrically resistive additives. The electrically resistive additives reduce the conductivity of the electrolyte composition.

[0036] The one or more chelating agents can include one or more groups selected from the group consisting of amine groups, amide groups, carboxylate groups, dicarboxylate groups, tri-carboxylate groups, and combinations thereof. The one or more chelating agents can include ethylenediamine, hexadiamine, amino acids, ammonium oxalate, ammonium citrate, ammonium succinate, citric acid, monobasic potassium citrate, dibasic potassium citrate, tribasic potassium citrate, tartaric acid, potassium tartarate, ammonium tartarate, succinic acid, potassium succinate, oxalic acid, potassium oxalate, and combinations thereof. The electrolyte composition may include between about 0.1% and about 15% by volume or weight of the one or more chelating agents.

[0037] Polymeric inhibitors that may be used include polyalkylaryl ether phosphate, ammonium nonylphenol ethoxylate sulfate, polyammonium nonylphenol ethoxylate sulfate, sulfates of nonylphenol ethoxylate, phosphates of nonylphenol ethoxylate, potassium derivatives of nonylphenol ethoxylate sulfate, phosphate derivatives of alkylphenol ethoxylate, sulfate derivatives of alkylphenol ethoxylate, phosphate derivatives of alkylether, sulfate derivatives of alkylether, phosphate derivatives of alkyl alkanol amide, sulfate derivatives of alkyl alkanol amide, polyalkoxylated amide, and combinations thereof. The electrolyte composition may include between about 0.002% and about 1.0% by volume or weight of the polymeric inhibitor.

[0038] The one or more pH adjusting agents contribute to the pH adjustment of the electrolyte composition. The preferred pH of the electrolyte composition is typically between about 3 and about 10. pH adjusting agents that can be used include acetic acid, citric acid, oxalic acid, phosphate-containing components, or combinations thereof. Phosphate-containing components that can be used include phosphoric acid, ammonium phosphates, potassium phosphates, or combinations thereof. The electrolyte composition may include between about 0.2% and about 25% by volume or weight of the one or more pH adjusting agents.

[0039] The one or more electrically resistive additives are additives that reduce the conductivity of the electrolyte composition. The electrically resistive additives can include polyacrylamide, polyacrylic acid polymers, polycarboxylate copolymers, coconut diethanolamide, oleic diethanolamide, ethanolamide derivatives, or combinations thereof. The electrolyte composition may include between about 0.005% and about 2% by volume or weight of the electrically resistive additives.

[0040] The balance or remainder of the electrolyte compositions described above typically is or includes deionized water.

[0041] The conductivity of the electrolyte compositions comprising one or more chelating agents, one or more corrosion inhibitors comprising one or more polymeric inhibitors, one or more pH adjusting agents, and one or more electrically resistive additives, may be less than about 30 milliSiemens, such as about 15 milliSiemens. The conductivity of other types of electrolyte compositions that do not include electrically resistive additives can be between about

[0042] 40 milliSiemens and about 100 milliSiemens.

[0043] An example of an electrolyte composition that includes one or more chelating agents, one or more corrosion inhibitors comprising one or more polymeric inhibitors, one or more pH adjusting agents, and one or more electrically resistive additives is an electrolyte composition that includes about 4% by volume ethylenediamine, about 0.2% by volume ammonium nonylphenol ethoxylate sulfate, about 5% by volume phosphoric acid, and about 0.3% by volume oleic diethanolamide. The pH of the electrolyte composition is about 6.0. The remainder of the electrolyte composition is deionized water.

[0044] Although the electrolyte compositions described herein are thought to be useful with ECMP, electropolishing, and chemical polishing systems, the electrolyte compositions may be used particularly to advantage in an ECMP process station. A typical ECMP process station is a modified cell on an Electra Cu Integrated ECP system, available from Applied Materials, Inc. of Santa Clara, Calif. A typical ECMP process station may also be a modified platen on a Reflexion/Mirra MESA Integrated CMP system, both available from Applied Materials, Inc. of Santa Clara, Calif.

[0045] FIG. 1 illustrates a partial section view of a polishing station 102. As shown, the polishing station 102 generally includes a basin 202, a first electrode 204, a second electrode 207, a cover 208, and a polishing head 130. The polishing head 130 provides support for a wafer/substrate 114 disposed thereon. Although the polishing station 102 depicts a wafer face down configuration, the electrolyte composition 220 may also be used to advantage within a processing chamber utilizing a wafer face up configuration. In this alternative configuration, the wafer would rest with its plating side up and the pad would be disposed on the plating surface of the wafer.

[0046] Referring to FIG. 1, the first electrode 204 is disposed within the basin 202 and is a conventional electrode having a reactive bias applied thereto to act as a cathode. The first electrode 204 may be made of the metal to be removed from the substrate 114, which may consist of aluminum, copper, gold, silver, or tungsten, for example. Accordingly, for copper removal, the first electrode 204 consists of copper containing materials.

[0047] The second electrode 207 is also disposed within the basin 202 and may take the form of a polishing media 205 supported on a lower surface by a perforated disc 206. The polishing media 205 is used to apply a uniform bias to the substrate surface without the use of a conventional bias application apparatus, such as an edge contact. The polishing media 205 can be a pad, web, or belt of material that includes a partially conductive surface for contact with the substrate surface during processing. The partially conductive surface of the polishing media 205 may include materials, such as conductive polymers, polymer composites with conductive materials, conductive metals, conductive fillers, conductive doping materials, or combinations thereof. The partially conductive surface of the polishing media 205 may also be a composite of a conductive polishing material disposed in a conventional polishing material, such as a polymer-noble metal hybrid material like a platinum-polymer hybrid material. The partially conductive surface of the polishing media 205 is described in more detail in the co-pending U.S. patent application Ser. No. 10/033,732, entitled Conductive Polishing Media For Electrochemical Mechanical Polishing, filed on Dec. 27, 2001, which is incorporated by reference herein.

[0048] The basin 202 can be a bowl shaped member made of a plastic such as fluoropolymers, TEFLON, PFA, PE, PES, or other materials that are compatible with electroplating and electropolishing chemistries. The basin 202 has a bottom 210 that includes an aperture 216 and a drain 214. The aperture 216 is generally disposed in the center of the bottom 210 and allows a shaft 212 to pass there-through. A seal 218 is disposed between the aperture 216 and the shaft 212 and allows the shaft 212 to rotate while preventing fluids disposed in the basin 202 from passing through the aperture 216.

[0049] The electrolyte composition 220 is introduced into the polishing station 102 through a supply line 244. The electrolyte composition 220 is disposed in the basin 202 and generally flows out of the polishing station 102 through the drain 214.

[0050] A substrate 114 is disposed on the substrate support 130 which may be a polishing head used in a chemical mechanical planarization process as shown. The substrate support 130 typically applies a pressure in the range of about 0.1 psi to about 1 psi to the substrate surface to be electrochemically and mechanically polished. On the substrate support 130, the substrate 114 is exposed to the electrolyte composition 220 and contacted with the second electrode 207. A bias from a power source 200 is then applied to both electrodes 204 and 207. The bias typically ranges from about 15 volts to about 15 volts. In one aspect, the positive bias ranges from about 0.1 volts to about 10 volts and the negative bias ranges from about 0.1 to about 10 volts. Alternatively, the bias may be a current density between about 0.01 and about 40 milliamps/cm² for a 200 mm substrate. The bias may be varied in power and application depending upon the user requirements in removing material from the substrate surface. The bias may also be applied by an electrical pulse modulation technique, which applies a constant current density or voltage for a first time period, then applies a constant reverse current density or voltage for a second time period, and repeats the first and second steps, as is described in co-pending U.S. patent application Ser. No. 09/450,937, entitled Method And Apparatus For Electrochemical Mechanical Planarization, filed on Nov. 29, 1999, which is incorporated by reference herein.

[0051] To facilitate control of the polishing process, a controller 140 comprising a central processing unit (CPU) 142, memory 144, and support circuits 146, is connected to the polishing station 102. The CPU 142 may be one of any form of computer processors that are used in industrial settings for controlling various drives and pressures. The memory 144 is connected to the CPU 142, and may be one or more of a readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. Software instructions and data can be coded and stored within the memory 144 for instructing the CPU 142. The support circuits 146 are also connected to the CPU 142 for supporting the processor 142 in a conventional manner. The support circuits 146 may include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like.

[0052] Other systems may be used with the electrolyte compositions described herein to planarize or polish substrates. For example, the polishing systems described in co-pending U.S. Provisional Patent Application serial No. 60/342,281, entitled Method And Apparatus For Face-Up Substrate Polishing, filed on Dec. 19, 2001 and incorporated by reference herein, and in co-pending U.S. patent application Ser. No. 09/770,559, entitled Electro-Chemical Plating With Reduced Thickness And Integration With Chemical Mechanical Polisher Into A Single Platform, filed on Jan. 26, 2001 and incorporated by reference herein may be used.

[0053] The following non-limiting examples are provided to further illustrate the embodiments of the invention. However, the examples are not intended to be all inclusive and are not intended to limit the scope of the invention described herein above.

[0054] A copper plated wafer was polished and planarized using the following electrolyte composition within a modified cell on an Electra Cu Integrated ECP system, available from Applied Materials, Inc. of Santa Clara, Calif.

[0055] about 2% by volume ethylenediamine;

[0056] about 2% by weight ammonium citrate;

[0057] about 0.2% by weight benzotriazole;

[0058] about 6% by volume phosphoric acid;

[0059] between about 2% and about 6% potassium hydroxide; and deionized water

[0060] The pH of the composition was about 6.0.

[0061] A copper plated wafer was polished and planarized using the following electrolyte composition within a modified cell on an Electra Cu Integrated ECP system, available from Applied Materials, Inc. of Santa Clara, Calif.

[0062] about 2% by volume ethylenediamine;

[0063] about 4% by weight ammonium citrate;

[0064] about 0.04% by weight benzotriazole;

[0065] about 6% by volume phosphoric acid;

[0066] about 0.3% by volume ammonium nonylphenol ethoxylate sulfate;

[0067] between about 2% and about 6% potassium hydroxide; and deionized water.

[0068] The pH of the composition was about 6.0.

[0069] A copper plated wafer was polished and planarized using the following electrolyte composition within a modified cell on an Electra Cu Integrated ECP system, available from Applied Materials, Inc. of Santa Clara, Calif.

[0070] about 4% by volume ethylenediamine;

[0071] about 0.2% by volume ammonium nonylphenol ethoxylate sulfate;

[0072] about 5% by volume phosphoric acid;

[0073] about 0.3% by volume oleic diethanolamide; and deionized water.

[0074] The pH of the composition was about 6.0.

[0075] 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.