Polyurethane polishing pad and preparation method thereof

Abstract

The invention provides a polyurethane polishing pad and a preparation method thereof, the polyurethane polishing pad comprises a polyurethane mixture, the polyurethane mixture comprises a polyurethane prepolymer, a curing agent and a heat dissipation filler; in the polyurethane mixture, the mass percent of the polyurethane prepolymer is 50%-90%, the mass percent of the curing agent is 10%-30%, and the mass percent of the modified filler is 1%-10%; the water-soluble polymer compound system comprises polyvinylpyrrolidone, carboxymethyl cellulose and polyethylene glycol, the water-soluble polymer compound system is characterized in that the polyvinylpyrrolidone and the carboxymethyl cellulose are grafted to form a grafted copolymer, the grafted copolymer is compounded with the polyethylene glycol, and the mass ratio of the polyvinylpyrrolidone to the carboxymethyl cellulose in the grafted copolymer is 10: (1-2). The heat dissipation filler is added into the polyurethane, so that an effective heat dissipation effect can be achieved, the polishing uniformity is prevented from being affected by overheating of the polishing pad and the wafer, and the surface temperature of the polished wafer is moderate.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical mechanical polishing, in particular to a polyurethane polishing pad and a preparation method thereof. Background Art

[0002] Chemical mechanical polishing (CMP) is a core process for achieving global planarization of wafer surfaces in semiconductor manufacturing. It is a polishing technique that combines mechanical grinding with chemical polishing solutions. The CMP process involves securing the workpiece to a support. The surface to be polished is pressed downward against a polishing pad with a constant pressure. The workpiece and polishing pad are then rotated relative to each other. In the presence of a polishing solution, mechanical cutting by the abrasive and chemical etching by an oxidizing agent remove material from the workpiece surface, resulting in a smooth surface. Polyurethane polishing pads are currently the most widely used type of polishing pad in high-precision polishing. Traditional polyurethane polishing pads are mostly prepared by reacting a polyol with a polyisocyanate to form an isocyanate-terminated urethane prepolymer. Patent Publication No. CN107457716A discloses a polishing layer for a CMP pad. This polishing layer is produced by reacting a polyol, a polyamine, and a polyisocyanate. The polyol is a mixture of polytetramethylene ether polyol and polyester polyol. Hollow polymer microspheres are added to create a porous structure. However, these common polyurethane porous membranes are difficult to control the distribution of hollow polymer microspheres, resulting in uneven pore distribution and varying pore sizes in the final membrane, which in turn affects the polishing performance.

[0003] In the prior art, patent publication number CN115958526A discloses a chemical mechanical polishing pad with high polishing stability and its preparation method. The method comprises dissolving a water-soluble polymer in a solvent to prepare a solution, adding the solution to a resin solution, coating the solution on a plastic film substrate, and obtaining a porous resin film by a coagulation film formation method. The water-soluble polymer is then dissolved in a water washing process to form micropores, and finally, a polishing pad is prepared by post-processing. The water-soluble polymer is readily soluble in water. Therefore, during the coagulation film formation process of the resin solution, the water-soluble polymer regulates the resin slurry coagulation and solvent displacement process, and simultaneously forms tiny, interconnected micropores within the coagulated resin, allowing the polishing liquid to flow alternately within adjacent teardrop-shaped pores and be more evenly supplied to the polishing interface. However, the use of a single type of water-soluble polymer in this prior art makes it difficult to balance the solvent displacement rate and pore structure uniformity, resulting in poor micropore penetration, which in turn affects the pore structure uniformity. In the prior application, the applicant employed a composite system of multiple water-soluble polymers, leveraging their properties to enhance microporous structure uniformity and significantly reduce roughness. However, during use, it was discovered that for polishing layers with lower roughness, this reduced the heat dissipation efficiency of the polishing pad during polishing, affecting polishing uniformity. Summary of the Invention

[0004] In view of this, the present invention aims to propose a polyurethane polishing pad and a preparation method thereof to solve the problem in the prior art that the roughness and heat dissipation efficiency of polyurethane polishing pads containing water-soluble polymers cannot be taken into account at the same time, which affects the polishing uniformity.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A polyurethane polishing pad comprises the following raw material components:

[0007] A polyurethane mixture, comprising a polyurethane prepolymer, a curing agent, and a heat dissipating filler; wherein the polyurethane prepolymer is 50% to 90% by mass, the curing agent is 10% to 30% by mass, and the modified filler is 1% to 10% by mass;

[0008] The water-soluble polymer compound system includes polyvinyl pyrrolidone (PVP), carboxymethyl cellulose (CMC), and polyethylene glycol (PEG). The water-soluble polymer compound system is a graft copolymer formed by grafting polyvinyl pyrrolidone and carboxymethyl cellulose, and then compounded with polyethylene glycol. The mass ratio of polyvinyl pyrrolidone to carboxymethyl cellulose in the graft copolymer is 10:1~2.

[0009] Furthermore, the polyurethane mixture is a dispersion system formed by dissolving and / or dispersing a polyurethane prepolymer, a curing agent, and a modified filler in a solvent N,N-dimethylformamide (DMF).

[0010] Furthermore, the heat dissipation filler is graphene.

[0011] Furthermore, at least part of the polyethylene glycol is acid-modified polyethylene glycol.

[0012] Furthermore, the acid-modified polyethylene glycol is polyethylene glycol graft-modified with polyacrylic acid, and the mass ratio of polyethylene glycol to polyacrylic acid in the graft copolymer of the two is 10-20:1.

[0013] Furthermore, the weight ratio of polyethylene glycol, polyethylene glycol graft copolymer and polyvinyl pyrrolidone graft copolymer is 1:0.2-0.5:1-1.5.

[0014] A method for preparing a polyurethane polishing pad comprises the following steps:

[0015] (1) Preparation of polyurethane mixture: Heat the polyurethane prepolymer to about 80°C, evenly disperse the heat dissipation filler in the prepolymer, degas under vacuum conditions for about 60-80 minutes, add the curing agent, stir evenly, pour into the mold for curing, and form a thermoplastic polyurethane block structure;

[0016] (2) Dissolve the graft copolymer of polyvinylpyrrolidone carboxymethyl cellulose and PEG in DMF to form a homogeneous mixture; (2) Blend the mixture with molten polyurethane and coat it on a PET or non-woven fabric substrate; (3) Immerse in DMF solution for coagulation; (4) Circulate and squeeze with clean water to remove water-soluble polymer residues, dry and sand it to form a microporous membrane structure.

[0017] Furthermore, in step (1), the heat dissipation filler is graphene coated with boron nitride.

[0018] Furthermore, the polyvinyl pyrrolidone is added in a continuous manner.

[0019] Furthermore, the product is immersed in a 20-25% DMF solution for coagulation, the coagulation temperature is 10-50° C., the coagulation time is 5-15 minutes, and the coagulation liquid is a DMF aqueous solution.

[0020] Compared with the prior art, the polishing pad with uniform density described in the present invention has the following advantages:

[0021] Adding heat-dissipating fillers to polyurethane effectively dissipates heat, preventing overheating of the polishing pad and wafer, which can affect polishing uniformity. Furthermore, mixing amino-modified boron nitride with graphene enhances the dispersion of the thermally conductive filler in the polyurethane mixture, improving its uniformity and preventing precipitation during the coating process. Furthermore, the contact between the boron nitride flakes and the graphene granules forms an uninterrupted heat-conducting network, ensuring uniform heat dissipation across all locations on the polishing pad and maintaining a moderate surface temperature on the polished wafer.

[0022] By grafting polyvinyl pyrrolidone onto carboxymethyl cellulose and acidifying polyethylene glycol, it was found that the stability of the mixture could be significantly improved, preventing rapid phase separation. Furthermore, microporous membranes prepared by mixing the grafted polymer with molten polyurethane exhibited high porosity, and the resulting polishing pads exhibited high polishing removal rates.

[0023] When performing segmented coagulation, the polyurethane resin membrane can be first dissolved in a 22% DMF aqueous solution to quickly form a uniform microporous skeleton. After being removed and left for a period of time, a high-concentration DMF aqueous solution is then used for rapid coagulation in a short period of time. This allows the high-concentration DMF aqueous solution to quickly enter the micropores and dissolve the pore walls, facilitating rapid connection between the micropores. Furthermore, the immersion time in the high-concentration DMF aqueous solution should not be too long to prevent the pore diameter from becoming larger. Finally, a low-concentration DMF solution is used to slowly act to make the surface smooth. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below.

[0025] A polyurethane polishing pad comprises the following raw material components:

[0026] polyurethane blends;

[0027] The water-soluble polymer compound system includes polyvinyl pyrrolidone (PVP), carboxymethyl cellulose (CMC), and polyethylene glycol (PEG).

[0028] The polyurethane mixture includes a polyurethane prepolymer, a curing agent and a modified filler; in the polyurethane mixture, the mass percentage of the polyurethane prepolymer is 50% to 90%, the mass percentage of the curing agent is 10% to 30%, and the mass percentage of the modified filler is 1% to 10%.

[0029] The relative molecular weight of polyethylene glycol is 10,000 to 30,000, and the average relative molecular weight of polyvinyl pyrrolidone is 5,000 to 30,000. Preferably, the relative molecular weight of the polyethylene glycol used is 20,000.

[0030] As a preferred embodiment of the present invention, the water-soluble polymer compound system can be a graft copolymer formed by grafting polyvinyl pyrrolidone and carboxymethyl cellulose, and then compounded with polyethylene glycol. The mass ratio of polyvinyl pyrrolidone to carboxymethyl cellulose in the graft copolymer is 10:1-2.

[0031] At least part of the polyethylene glycol is acid-modified polyethylene glycol to improve the pH value of the compound system and reduce the possibility of polymer precipitation or gel formation in the compound system.

[0032] Furthermore, the acid-modified polyethylene glycol is polyethylene glycol graft-modified with polyacrylic acid, and the mass ratio of polyethylene glycol to polyacrylic acid in the graft copolymer of the two is 10-20:1.

[0033] The weight ratio of polyethylene glycol, graft-modified polyethylene glycol and polyvinyl pyrrolidone graft copolymer is 1:0.2-0.5:1-1.5.

[0034] The polyurethane mixture is a dispersion system formed by dissolving and / or dispersing a polyurethane prepolymer, a curing agent and a modified filler in a solvent N,N-dimethylformamide (DMF).

[0035] A method for preparing a polyurethane polishing pad comprises the following steps:

[0036] (1) Preparation of modified filler: Weigh an appropriate amount of boron nitride, calcine it at 800-1000°C for 2h, disperse the calcined boron nitride in deionized water, ultrasonically disperse the calcined boron nitride, prepare a boron nitride dispersion with a concentration of 5 mg / mL, ultrasonically disperse it for 1h, add glacial acetic acid to adjust the pH of the boron nitride dispersion to 4, add silane coupling agent (KH-550), and stir at a constant temperature of about 30°C to obtain amino-modified boron nitride. The mass ratio of the above-mentioned silane coupling agent (KH-550) to boron nitride is 0.5-1:100 by weight.

[0037] Graphene oxide is added to the mixed solution of the amino-modified boron nitride, stirred at a constant temperature of 30-50° C. for 2-4 hours, and then centrifugally dried to obtain a modified filler.

[0038] (2) Preparation of polyurethane mixture: Heat the polyurethane prepolymer to about 80°C, evenly disperse the modified filler in the prepolymer, degas under vacuum conditions for about 60 to 80 minutes, add the curing agent, stir evenly, pour into the mold for curing, and form a thermoplastic polyurethane block structure.

[0039] The polyurethane prepolymer is an isocyanate-terminated prepolymer (the mass percentage of unreacted NCO groups is 8.75-9.05%). The curing agent is 1,4-butanediol. The feed ratio of polyurethane prepolymer to curing agent and heat dissipation filler is 100:7-12:5-12 in parts by weight.

[0040] (3) Preparation of graft copolymer of polyvinylpyrrolidone and carboxymethyl cellulose: Take an appropriate amount of carboxymethyl cellulose and perform plasma treatment, then dissolve the plasma-treated carboxymethyl cellulose in deionized water, dissolve benzoyl peroxide in the solution, and add the mixed solution into a vacuum reactor, or introduce nitrogen to keep the reaction under anaerobic conditions.

[0041] The polyvinyl pyrrolidone solution is added to the above mixed solution by continuous feeding, and a viscous liquid is obtained after a certain reaction time. The product is placed in an environment of 60°C and vacuum dried to a constant weight to obtain a solid product, which is a graft copolymer of polyvinyl pyrrolidone and carboxymethyl cellulose.

[0042] The vacuum degree of the plasma treatment is set to 250-300 Pa, the power is set to 200-300 W, and the treatment time is set to 120-200 s. The temperature of the reactor for the grafting reaction is controlled at 60-80°C.

[0043] Calculated by weight, the amount of benzoyl peroxide used is 2% to 3% of the total amount of polyvinyl pyrrolidone and carboxymethyl cellulose.

[0044] (4) Preparation of acid-modified polyethylene glycol: Disperse polyacrylic acid in water, add aminopolyethylene glycol monomethyl ether to the polyacrylic acid aqueous solution at once, and react at 50-60°C for 10-12 hours to obtain an acid-modified polyethylene glycol graft copolymer aqueous solution. After the reaction is completed, filter, wash with deionized water, and dry to obtain the acid-modified polyethylene glycol.

[0045] The molecular weight of the polyacrylic acid is 8,000 to 30,000, and the molecular weight of the aminopolyethylene glycol monomethyl ether is 10,000 to 30,000. The ratio of polyethylene glycol to aminopolyethylene glycol monomethyl ether is 1 to 2:10, calculated by weight.

[0046] (5) dissolving the graft copolymer of polyvinylpyrrolidone carboxymethyl cellulose, acid-modified polyethylene glycol, and unmodified polyethylene glycol in DMF to form a homogeneous mixture, i.e., a water-soluble polymer solution, wherein the solid content of the solution is 20-40%; melting the block-shaped thermoplastic polyurethane obtained in step (2) to form a viscous fluid, uniformly mixing the molten polyurethane mixture with the above homogeneous mixture, coating it on a transparent film or non-woven fabric substrate, and cutting it to form a sheet structure;

[0047] Calculated by weight, the feed ratio of the graft copolymer of polyvinyl pyrrolidone carboxymethyl cellulose, the acid-modified polyethylene glycol, and the unmodified polyethylene glycol is 1-1.5:0.2-0.5:1.

[0048] When the molten polyurethane is mixed with the water-soluble polymer solution, the mixing temperature is controlled to be 60~100℃ to avoid polyurethane agglomeration during the mixing process.

[0049] Calculated by weight, the ratio of molten polyurethane to the above mixture solution is 25-50:5-20.

[0050] (6) Immersing the sheet structure obtained in step (5) in a condensation liquid for condensation to obtain a polishing pad with uniform density; the condensation temperature is 10-50°C, the condensation time is 5-15 minutes, and the condensation liquid is an aqueous solution of DMF.

[0051] (7) Use deionized water circulation to clean and squeeze to remove water-soluble polymer residues, dry and sand to form a microporous membrane structure.

[0052] As a preferred embodiment, the solution is sequentially immersed in a 20-25% DMF aqueous solution, a 25-30% DMF aqueous solution, and a 15-18% DMF aqueous solution for segmented coagulation;

[0053] Example 1

[0054] (1) Dissolve 1.5 g of carboxymethyl cellulose, 8 g of polyvinyl pyrrolidone, and 10 g of polyethylene glycol in 80 mL of DMF to form a homogeneous mixture. The average molecular weight of polyvinyl pyrrolidone is 8,000; the average molecular weight of polyethylene glycol is 20,000.

[0055] (2) 450 g of molten polyurethane resin was blended with the homogeneous mixture and evenly coated on the PET substrate;

[0056] (3) Immersing in a 22% DMF aqueous solution for condensation to obtain a porous resin membrane, soaking the resin membrane, cleaning and squeezing it, drying it, and sanding it to form a microporous membrane structure.

[0057] Example 2

[0058] (1) Preparation of polyvinylpyrrolidone-carboxymethyl cellulose graft copolymer: 100 g of carboxymethyl cellulose was layered in a plasma chamber. The vacuum degree of the plasma treatment was set to 250 Pa, the power was set to 200 W, and the treatment time was set to 150 s for plasma treatment. Then, 10 g of the plasma-treated carboxymethyl cellulose was dissolved in 100 mL of deionized water. At the same time, 2 g of benzoyl peroxide was dissolved in the solution. The mixed solution was added to a vacuum reactor, or nitrogen was introduced to keep the reaction under anaerobic conditions.

[0059] Dissolve 80g of polyvinylpyrrolidone in 1L of deionized water. Add the polyvinylpyrrolidone solution to the mixed solution over approximately two hours by continuous feeding. After reacting for 6 hours, a viscous liquid is obtained. The product is vacuum-dried at 60°C to a constant weight to obtain a solid product, which is a graft copolymer of polyvinylpyrrolidone and carboxymethylcellulose.

[0060] (2) Dissolve 10 g of polyvinylpyrrolidone carboxymethyl cellulose graft copolymer in 100 mL of DMF solvent, and add 10 g of polyethylene glycol to form a homogeneous mixture.

[0061] (3) Disperse 450 g of molten polyurethane resin in the above mixture and evenly coat it on the PET substrate;

[0062] (4) Immersing in a 22% DMF aqueous solution for condensation to obtain a porous resin membrane, soaking the resin membrane, cleaning and squeezing it, drying it, and sanding it to form a microporous membrane structure.

[0063] The relative molecular masses of polyvinyl pyrrolidone and polyethylene glycol in this embodiment are the same as those in Example 1.

[0064] Example 3

[0065] Step (1) is the same as in Example 2.

[0066] (2) Preparation of acid-modified polyethylene glycol: Disperse 1.5 g of polyacrylic acid in 100 mL of water, add 10 g of aminopolyethylene glycol monomethyl ether to the polyacrylic acid aqueous solution at once, and react at 50-60 °C for 10-12 hours to obtain an acid-modified polyethylene glycol graft copolymer aqueous solution. After the reaction is completed, filter, wash with deionized water, and dry to obtain the acid-modified polyethylene glycol.

[0067] The molecular weight of the polyacrylic acid is 2000-30000, and the molecular weight of the aminopolyethylene glycol monomethyl ether is 10000-30000.

[0068] (3) Dissolve 10 g of polyvinylpyrrolidone carboxymethyl cellulose graft copolymer and 2 g of acid-modified polyethylene glycol in 100 mL of DMF solvent, and add 8 g of polyethylene glycol to form a homogeneous mixture.

[0069] (4) Disperse 450 g of molten polyurethane resin in the above mixture and apply it on a transparent PET substrate;

[0070] (5) Immerse in a 22% DMF aqueous solution at a temperature of 40-50°C for 10 minutes to coagulate, and then obtain a porous resin membrane. Then, soak the resin membrane, wash it, squeeze it, dry it, and sand it to form a microporous membrane structure.

[0071] The relative molecular masses of polyvinyl pyrrolidone and polyethylene glycol in this embodiment are the same as those in Example 1.

[0072] Example 4

[0073] Steps (1) to (4) are the same as those in Example 3, except that:

[0074] (5) At a temperature of 40-50°C, immerse in a 22% DMF aqueous solution for 5 min and a 15% DMF aqueous solution for 5 min, respectively, to perform coagulation in two stages.

[0075] Example 5

[0076] Steps (1) to (4) are the same as those in Example 3, except that:

[0077] (5) At a temperature of 40-50°C, immerse in a 22% DMF aqueous solution for 5 min, a 30% DMF aqueous solution for 1 min, and a 15% DMF aqueous solution for 5 min, so as to perform coagulation in three stages.

[0078] Example 6

[0079] (1) Preparation of polyurethane mixture: 200 g of polyurethane prepolymer with a mass percentage of unreacted NCO groups of 9% was heated to about 80 °C, 10 g of graphene oxide was evenly dispersed in the prepolymer, and after degassing under vacuum conditions for about 60 min, a curing agent was added, stirred evenly, and poured into a mold for curing to form a thermoplastic polyurethane block structure.

[0080] (2) The steps of preparing the graft copolymer of polyvinylpyrrolidone carboxymethyl cellulose, preparing the acid-modified polyethylene glycol and forming a uniform mixture of the water-soluble polymer are the same as those in Example 5.

[0081] (3) 450 g of the molten polyurethane obtained in step (1) was blended with the above homogeneous mixture and evenly coated on a PET substrate;

[0082] The coagulation step is the same as in Example 5.

[0083] Example 7

[0084] (1) Preparation of modified filler: Weigh 10 g of boron nitride and calcine it at 800-1000 °C for 2 h. Disperse the calcined boron nitride in 2 L of deionized water. Ultrasonic disperse the calcined boron nitride for 1 h. Then, add glacial acetic acid to adjust the pH of the boron nitride dispersion to 4. Then, add 0.8 g of silane coupling agent KH-550 and stir at a constant temperature of about 30 °C to obtain amino-modified boron nitride.

[0085] 10 g of graphene oxide was added to the mixed solution of the amino-modified boron nitride, stirred at a constant temperature of 30-50° C. for 2-4 h, and then centrifuged and dried to obtain a modified filler.

[0086] (2) Preparation of a polyurethane mixture: replacing the graphene oxide therein with graphene modified with boron nitride, and the other steps are the same as those in Example 6.

[0087] Comparative Example 1

[0088] (1) Dissolve 10 g of carboxymethyl cellulose in 80 mL of DMF solvent to form a homogeneous mixture.

[0089] (2) 450 g of molten polyurethane resin was blended with the homogeneous mixture and coated on the PET substrate;

[0090] (3) Immersing in a 22% DMF aqueous solution for condensation to obtain a porous resin membrane, soaking the resin membrane, cleaning and squeezing it, drying it, and sanding it to form a microporous membrane structure.

[0091] Comparative Example 2

[0092] (1) Dissolve 10 g of polyvinyl pyrrolidone in 80 mL of DMF solvent to form a homogeneous mixture. The average relative molecular mass of polyvinyl pyrrolidone is 8000.

[0093] (2) 450 g of molten polyurethane resin was blended with the homogeneous mixture and coated on the PET substrate;

[0094] (3) Immersing in a 22% DMF aqueous solution for condensation to obtain a porous resin membrane, soaking the resin membrane, cleaning and squeezing it, drying it, and sanding it to form a microporous membrane structure.

[0095] Comparative Example 3

[0096] (1) Dissolve 10 g of polyethylene glycol pyrrolidone in 80 mL of DMF solvent to form a homogeneous mixture. The average molecular weight of polyethylene glycol is 20,000.

[0097] (2) 450 g of molten polyurethane resin was blended with the homogeneous mixture and coated on the PET substrate;

[0098] (3) Immersing in a 22% DMF aqueous solution for condensation to obtain a porous resin membrane, soaking the resin membrane, cleaning and squeezing it, drying it, and sanding it to form a microporous membrane structure.

[0099] The prepared polishing pad was subjected to a mercury intrusion test in accordance with GB / T 21650.1-2008 to measure the porosity of the microporous membrane obtained in each example.

[0100] Mixture stability test: In each example, after the molten polyurethane and the water-soluble polymer solution were mixed and blended and before coating to form a film, about 100 g of the blended mixture was taken out and allowed to stand. The standing condition of the mixed system was observed every 5 minutes.

[0101] Polishing performance test: A 30-inch polishing pad sample was attached to a CMP machine. The polishing slurry was Anji-D3000 at a flow rate of 300cc / min. The CMP machine was Universal-300B, with a pressure of 1.3psi, a grinding head speed of 85rpm, a grinding disc speed of 80rpm, and a polishing time of 90s / wafer. The wafer model was a 12-inch Teos wafer. The wafer polishing non-uniformity of the polishing pads used in each of the examples and comparative examples of this application was calculated using the method for calculating wafer removal non-uniformity described in background art document CN115958526A. The wafer surface temperature was also measured after polishing.

[0102] The polishing removal rate is the average value calculated by recording the removal rate during the polishing process using a four-probe film thickness meter (KLA Filmetrics R50).

[0103] The test results are shown in the following table:

[0104] Porosity Removal rate Non-uniformity Time for delamination to occur after standing still after blending with molten polyurethane / min Wafer surface temperature / ℃ Example 1 83.2% 1355 2.31 25 73 Example 2 84.5% 1279 2.45 30 79 Example 3 84.2% 1459 1.62 70 75 Example 4 87.3% 1523 1.16 60 80 Example 5 82.7% 1479 1.21 65 84 Example 6 88.3% 1604 1.02 50 68 Example 7 90.7% 1589 1.08 65 62 Comparative Example 1 84.9% 1106 5.61 60 82 Comparative Example 2 85.3% 1147 5.93 70 85 Comparative Example 3 84.4% 1051 5.37 55 81

[0105] By comparing Examples 1 to 3 with the comparative examples, it was found that when three water-soluble polymers were compounded to prepare a microporous membrane, the porosity of the prepared microporous membrane was higher than that of a single water-soluble polymer, because the added polyvinyl pyrrolidone could adjust the solvent replacement rate during the coagulation process, and polyethylene glycol could increase the permeability between the micropores. However, due to the interaction between different molecules, the mixture sometimes became turbid and stratified or phase separated during the coating process, affecting the film formation process. However, by grafting polyvinyl pyrrolidone with carboxymethyl cellulose and acid-modifying polyethylene glycol, it was found that the stability of the mixture could be greatly improved, avoiding the phase separation phenomenon too quickly. In addition, the microporous membrane prepared by mixing the grafted modified polymer with molten polyurethane had a higher porosity, and the polishing pad prepared had a higher polishing removal rate.

[0106] By comparing Examples 3 to 5, it is found that when a three-stage condensation process is adopted, the polishing performance of the polishing pad can be greatly improved, thereby improving the non-uniformity of the removal amount of the test wafer.

[0107] Comparisons of Examples 5-7 reveal that the addition of thermally conductive fillers during the preparation of polyurethane polishing pads effectively dissipates heat, preventing overheating of the polishing pad and wafer, which can affect polishing uniformity. Furthermore, mixing amino-modified boron nitride with graphene enhances the dispersion of the thermally conductive filler in the polyurethane mixture, improving its uniform dispersion and preventing precipitation during the coating process. Furthermore, the contact between the boron nitride flakes and the graphene granules forms an uninterrupted thermal network, ensuring uniform heat dissipation across all locations on the polishing pad and maintaining a moderate surface temperature on the polished wafer.

[0108] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A polyurethane polishing pad, characterized in that: The raw material components include: A polyurethane mixture, comprising a polyurethane prepolymer, a curing agent, and a heat dissipating filler; wherein the polyurethane prepolymer is 50% to 90% by mass, the curing agent is 10% to 30% by mass, and the modified filler is 1% to 10% by mass; The water-soluble polymer compound system includes polyvinyl pyrrolidone (PVP), carboxymethyl cellulose (CMC), and polyethylene glycol (PEG). The water-soluble polymer compound system is a graft copolymer formed by grafting polyvinyl pyrrolidone and carboxymethyl cellulose, and then compounded with polyethylene glycol. The mass ratio of polyvinyl pyrrolidone to carboxymethyl cellulose in the graft copolymer is 10:1~2.

2. The polishing pad according to claim 1, wherein The polyurethane mixture is a dispersion system formed by dissolving and / or dispersing a polyurethane prepolymer, a curing agent and a modified filler in a solvent N,N-dimethylformamide (DMF).

3. The polishing pad according to claim 1, wherein The heat dissipation filler is graphene.

4. The polishing pad according to claim 1, wherein At least part of the polyethylene glycol is acid-modified polyethylene glycol.

5. The polishing pad according to claim 1, wherein The acid-modified polyethylene glycol is polyethylene glycol graft-modified with polyacrylic acid, and the mass ratio of polyethylene glycol to polyacrylic acid in the graft copolymer is 10-20:

1.

6. The polishing pad according to claim 1, wherein The weight ratio of polyethylene glycol, graft-modified polyethylene glycol and polyvinyl pyrrolidone graft copolymer is 1:0.2-0.5:1-1.

5.

7. A method for preparing a polyurethane polishing pad, characterized in that: The following steps are involved: (1) Preparation of polyurethane mixture: Heat the polyurethane prepolymer to about 80°C, evenly disperse the heat dissipation filler in the prepolymer, degas under vacuum conditions for about 60-80 minutes, add the curing agent, stir evenly, pour into the mold for curing, and form a thermoplastic polyurethane block structure; (2) dissolving the graft copolymer of polyvinylpyrrolidone carboxymethyl cellulose and PEG in DMF to form a homogeneous mixture; (2) blending the mixture with molten polyurethane and coating it on a PET or non-woven fabric substrate; (3) Immersing in DMF solution for coagulation; (4) Cleaning and squeezing with clean water to remove water-soluble polymer residues, drying and sanding to form a microporous membrane structure.

8. The method for preparing a polishing pad according to claim 7, wherein: In step (1), the heat dissipation filler is graphene coated with boron nitride.

9. The method for preparing a polishing pad according to claim 7, wherein: The polyvinyl pyrrolidone is added in a continuous manner.

10. The method for preparing a polishing pad according to claim 7, wherein: Immerse in 20-25% DMF solution for coagulation, the coagulation temperature is 10-50°C, the coagulation time is 5-15 minutes, and the coagulation liquid is a DMF aqueous solution.