Acidic chemical mechanical polishing solution

Abstract

The invention relates to an acidic chemical mechanical polishing solution. The polishing solution comprises grinding particles, a polymer containing sulfonate radicals, a water-based liquid medium and other auxiliaries. According to the polishing solution disclosed by the invention, under an acidic condition, a polymer containing sulfonate radicals can accelerate hydrolysis of the surface of silicon nitride in a polishing process, so that the removal rate of an abrasive to the silicon nitride is improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor material processing technology, and specifically relates to an acidic chemical mechanical polishing slurry. Background Technology

[0002] Semiconductor technology, as the foundation of modern electronics, has become a core component of various electronic products. Integrated circuits (ICs) are a representative achievement of semiconductor technology, integrating millions of transistors, capacitors, resistors, and other electronic components onto a single chip, thereby achieving miniaturization and high performance in electronic devices. In the IC manufacturing process, the silicon nitride layer serves multiple functions, including dielectric isolation, passivation protection, photolithography masking, and stress regulation. Therefore, to improve the quality and reliability of ICs, high-precision chemical mechanical polishing of silicon nitride is necessary.

[0003] Chemical mechanical polishing (CMP) planarization is an essential part of semiconductor manufacturing processes. Its function is to remove defects, contaminants, and residual layers from the surface of silicon nitride (SiN), making the surface smooth and uniform, thereby improving the quality and performance of SiN. In the development of semiconductor technology, SiN polishing slurries have been continuously upgraded and improved to adapt to new process requirements and material properties. With the miniaturization and increasing integration of semiconductor devices, the requirements for SiN surface quality are becoming increasingly stringent, making the research and development of polishing slurries increasingly important. Currently, research on SiN polishing slurries mainly focuses on improving polishing efficiency and stability, reducing costs, and minimizing environmental pollution. With the continuous advancement and development of SiN manufacturing processes, the research and development of silicon-based polishing slurries will continue to advance to meet the needs of the semiconductor industry.

[0004] Silicon nitride polishing slurries are playing an increasingly prominent role in semiconductor manufacturing processes. Silicon nitride undergoes hydrolysis in water, but this process is relatively weak, with a hydrolysis rate of only about 0.5%. Under acidic conditions, the hydrolysis reaction of silicon nitride is significantly enhanced. Under acidic conditions, the hydrolysis products of silicon nitride include silicon oxide-like substances, SiO₂. - Compared to silicon nitride, materials like SiOH have significantly lower hardness and are easier to remove during polishing. However, in most applications of silicon nitride polishing slurries, the polishing rate is already insufficient, making the development of silicon nitride polishing accelerators an urgent priority. Summary of the Invention

[0005] The purpose of this invention is to provide an acidic chemical mechanical polishing slurry to solve the problem of low polishing rate of silicon nitride polishing slurries in the prior art, especially the low polishing rate of silicon nitride polishing slurries under acidic conditions.

[0006] The present invention provides an acidic chemical mechanical polishing slurry comprising abrasive particles, a sulfonate-containing polymer, an aqueous liquid medium, and other additives.

[0007] Preferably, the pH range of the polishing solution is 1-6, more preferably 1.6-5.

[0008] Preferably, the abrasive particles comprise one or more of the following: silicon dioxide, alumina, aluminum-doped silicon dioxide, aluminum-coated silicon dioxide, cerium dioxide, titanium dioxide, and polymer abrasive particles.

[0009] More preferably, the abrasive particles are silicon dioxide, including fumed silicon dioxide, molten silicon dioxide, and colloidal silicon dioxide, wherein the silicon dioxide content is 80 wt% or more.

[0010] Preferably, the particle size of the grinding particles is 20~150 nm, more preferably 30~120 nm.

[0011] Preferably, the polishing fluid contains 0.1% to 45% abrasive particles by mass percentage.

[0012] Preferably, the general chemical formula of the sulfonate-containing polymer is: R2 is H or a positively charged ion, and R1 is an organic structure such as alkyl, alkenyl, alkynyl, aromatic or heterocyclic.

[0013] More preferably, the sulfonate-containing polymer is at least one of polyethylene sulfate, polyethylene sulfonic acid, polynaphthalene sulfonic acid, polyethylene glycol methyl ether toluene sulfonate, polyanisine sulfonic acid, polymethyl methacrylate sulfonic acid, polysulfonated ether ketone, polyethylene sulfonate, polyacrylamide sulfonic acid, poly4-vinylbenzene sulfonic acid, polysulfonated styrene divinylbenzene, polysulfonated biphenyl ether, polysulfonated benzimidazole, polysulfonated carbazole, polysulfonated polysulfone, sulfonated polyarylene ether phosphine, polynaphthalene sulfonic acid, polysulfonated thiophene, polysulfonated naphthylamine, sulfonated polyphenylquinoxaline, and / or at least one salt of the above compounds.

[0014] Preferably, the content of sulfonate-containing polymers in the polishing solution is 10-200,000 ppm, more preferably 50-6,000 ppm.

[0015] The sulfonate-containing polymer is polymerized with other polymer monomers to form a copolymer, which is then added to the polishing solution. The other polymer monomers are at least one of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, 4-acryloylmorpholine, dihydroxyethyl acrylate, butyl acrylate, tert-butylacrylamide, styrene, vinyl chloride, vinyl acetate, methyl methacrylate, acrylonitrile, 1,3-butadiene, N-vinylpyrrolidone, maleic acid, and / or at least one salt of the above compounds.

[0016] Preferably, the other additives include at least one of pH adjusters, viscosity adjusters, or chelating agents.

[0017] Preferably, the pH adjuster is an inorganic acid or a single organic acid; the inorganic acid includes one of nitric acid, hydrochloric acid, and sulfuric acid, or a combination of the above inorganic acids and their salts; the organic acid includes one of formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, oxalic acid, succinic acid, lactic acid, malic acid, tartaric acid, citric acid, benzoic acid, salicylic acid, ascorbic acid, quinic acid, palmitic acid, and stearic acid, and the content of organic acid in the polishing solution is preferably 50~20000 ppm, more preferably 100~1000 ppm.

[0018] Furthermore, the pH adjuster may also contain a pH buffer system, such as oxalate standard buffer solution, citrate standard buffer solution, tartrate buffer solution, phosphate buffer solution and acetate buffer solution, etc.; the content of the pH buffer system in the polishing solution is preferably 50~20000 ppm, more preferably 100~1000 ppm.

[0019] Preferably, the viscosity modifier comprises at least one of polyvinyl alcohol, polyacrylamide, polyethylene glycol, hydroxyethyl cellulose, methyl cellulose, hydroxymethyl cellulose, polyvinylpyrrolidone, polyamide, polyethylene glycol, polypropylene, and / or at least one salt of the above compounds; the viscosity modifier content in the polishing liquid is preferably 10-2000 ppm, more preferably 50-600 ppm.

[0020] Preferably, the chelating agent comprises at least one of ethylenediaminetetraacetic acid, diethyltriaminepentaacetic acid, N-(hydroxyethyl)ethylenediaminetriacetic acid, hypozinotriacetic acid, methylglycine diacetic acid and / or at least one salt of the above compounds; the content of the chelating agent in the polishing solution is preferably 0.01~5% by mass percentage, more preferably 0.5~3%.

[0021] Beneficial effects

[0022] The polishing solution of the present invention contains a polymer containing sulfonate. Under acidic conditions, the polymer containing sulfonate can accelerate the hydrolysis of silicon nitride surface during polishing, thereby increasing the removal rate of silicon nitride by the abrasive. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the mechanism of action of sulfonate ions in the polishing solution of the present invention. Detailed Implementation

[0024] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0025] This invention uses silica microspheres with a particle size of 50 nm as abrasive particles (15% by mass), adds different polymers containing sulfonates, mixes them evenly with water, and adjusts the pH value to a suitable level using organic or inorganic acids to prepare various polishing solutions. The specific components and contents are shown in Table 1.

[0026] Silicon nitride was polished using the aforementioned polishing slurry. The polishing process parameters were as follows: downward pressure 4 psi, polishing disc (8-inch diameter) rotation speed 87 rpm, polishing head rotation speed 93 rpm, polishing slurry flow rate 200 ml / min, polishing pad IC1010, and polishing machine AP-300. The polishing time was 1 minute. The polishing results are shown in Table 1. Compared with the polishing slurries of Comparative Examples 1-3, the polishing slurry of this invention, which contains a polymer containing sulfonate, significantly improved the removal rate of silicon nitride.

[0027] Table 1. Formulations of polishing slurries and their silicon nitride removal rates in Examples 1-18 and Comparative Examples 1-3.

[0028]

[0029] The polishing solution of this invention contains a polymer containing sulfonate, such as... Figure 1 As shown, under acidic conditions, the Si atoms on the surface of the SiN thin film exhibit partial positive charge (δ) due to their charge distribution. +The oxygen atom in the sulfonate group (containing the -O-SO2-R1 structure) launches a nucleophilic attack on the Si atom, forming a Si-OS bond—this step achieves the binding of the sulfonate group to the SiN surface and activates the surface reaction sites. Subsequently, with the participation of water, the Si-OS bond undergoes a hydrolysis reaction and breaks, generating a Si-OH group, while the sulfonate structure is regenerated. This cycle of "nucleophilic binding-hydrolysis breaking" accelerates the removal efficiency of materials from the SiN surface, thus speeding up the polishing process.

Claims

1. An acidic chemical mechanical polishing slurry, characterized in that, The polishing fluid contains abrasive particles, a polymer containing sulfonate, water, and other additives.

2. The acidic chemical mechanical polishing slurry according to claim 1, characterized in that, The abrasive particles include one or more of silicon dioxide, aluminum oxide, aluminum-doped silicon dioxide, aluminum-coated silicon dioxide, cerium dioxide, titanium dioxide, and polymer abrasive particles; the particle size of the abrasive particles is 20~150 nm.

3. The acidic chemical mechanical polishing slurry according to claim 1, characterized in that, The general chemical formula of the sulfonate-containing polymer is: R2 is H or a positively charged ion, and R1 is an alkyl, alkenyl, alkynyl, aromatic or heterocyclic organic structure.

4. The acidic chemical mechanical polishing slurry according to claim 3, characterized in that, The sulfonate-containing polymer is at least one of the following: polyethylene sulfate, polyethylene sulfonic acid, polynaphthalene sulfonic acid, polyethylene glycol methyl ether toluene sulfonate, polyanisine sulfonic acid, polymethyl methacrylate sulfonic acid, polysulfonated ether ketone, polyethylene sulfonate, polyacrylamide sulfonic acid, poly4-vinylbenzene sulfonic acid, polysulfonated styrene divinylbenzene, polysulfonated biphenyl ether, polysulfonated benzimidazole, polysulfonated carbazole, polysulfonated polysulfone, sulfonated polyarylene ether phosphine, polynaphthalene sulfonic acid, polysulfonated thiophene, polysulfonated naphthylamine, sulfonated polyphenylquinoxaline, and / or at least one salt of the above compounds.

5. The acidic chemical mechanical polishing slurry according to claim 1, characterized in that, The polishing slurry contains 0.1% to 45% abrasive particles by mass percentage; the polishing slurry contains 10 to 200,000 ppm of polymers containing sulfonate groups.

6. The acidic chemical mechanical polishing slurry according to claim 1, characterized in that, The sulfonate-containing polymer is polymerized with other polymer monomers to form a copolymer, which is then added to the polishing solution; wherein the other polymer monomers are at least one of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, 4-acryloylmorpholine, dihydroxyethyl acrylate, butyl acrylate, tert-butylacrylamide, styrene, vinyl chloride, vinyl acetate, methyl methacrylate, acrylonitrile, 1,3-butadiene, N-vinylpyrrolidone, maleic acid and / or at least one salt of the above compounds.

7. The acidic chemical mechanical polishing slurry according to claim 1, characterized in that, The other additives include at least one of pH adjusters, viscosity adjusters, or chelating agents; the pH range of the polishing solution is 1-6.

8. The acidic chemical mechanical polishing slurry according to claim 7, characterized in that, The pH adjuster is an inorganic acid or a single organic acid; wherein the inorganic acid includes one of nitric acid, hydrochloric acid, and sulfuric acid, or a combination of the above inorganic acids and their salts; the organic acid is one of formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, oxalic acid, succinic acid, lactic acid, malic acid, tartaric acid, citric acid, benzoic acid, salicylic acid, ascorbic acid, quinic acid, palmitic acid, and stearic acid.

9. The acidic chemical mechanical polishing slurry according to claim 7, characterized in that, The viscosity modifier in the polishing solution comprises at least one of polyvinyl alcohol, polyacrylamide, polyethylene glycol, hydroxyethyl cellulose, methyl cellulose, hydroxymethyl cellulose, polyvinylpyrrolidone, polyamide, polyethylene glycol, polypropylene, and / or at least one salt of the above compounds; the content of the viscosity modifier in the polishing solution is 10-2000 ppm.

10. The acidic chemical mechanical polishing slurry according to claim 7, characterized in that, The chelating agent comprises at least one of ethylenediaminetetraacetic acid, diethyltriaminepentaacetic acid, N-(hydroxyethyl)ethylenediaminetriacetic acid, hypozinotriacetic acid, methylglycine diacetic acid, and / or at least one salt of the above compounds; the content of the chelating agent in the polishing solution is 0.01~5% by mass percentage.

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