Highly hydrophilic wear-resistant cmp polishing pad and its preparation method and application

Abstract

This invention relates to the field of chemical mechanical polishing (CMP) pad technology, specifically to a highly hydrophilic and wear-resistant CMP polishing pad, its preparation method, and its application. The invention uses cyanosiloxane monomers as raw materials, preparing highly active carboxylate silsesquioxane powder through one-step alkaline hydrolysis, and achieving nanoscale uniform dispersion of this powder in polyurethane. After pre-treating the base fabric with an acid-base oscillating impregnation agent, the nanoscale uniformly dispersed slurry is coated onto the base fabric, and then solidified to obtain the target product. This invention solves the technical problems of difficulty in balancing hydrophilicity and wear resistance, and poor polishing uniformity in existing hydrophilic modification polishing pads. The polishing pad produced is used for wafer polishing, exhibiting less than 3% intra-wafer non-uniformity, fewer surface defects, and extended service life. The process of this invention is fully compatible with existing wet production lines for polyurethane polishing pads, requiring no additional equipment. The process is simplified, batch stability is strong, and industrial mass production is possible, adapting to the high-precision, low-defect polishing requirements of advanced semiconductor processes below 14nm.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing pad technology, specifically to a highly hydrophilic and wear-resistant CMP polishing pad, its preparation method, and its application. Background Technology

[0002] Chemical mechanical polishing (CMP) is a core process for achieving global planarization in semiconductor wafer manufacturing, and currently the only technology capable of achieving wafer-level nanometer-precision global planarization. As a critical consumable, the surface wettability, pore structure, compression resilience, and wear and corrosion resistance of CMP polishing pads directly determine the wafer's polishing uniformity, material removal rate (MRR) stability, surface defect rate, product yield, and manufacturing cost. With the evolution of semiconductor processes towards advanced nodes of 14nm, 7nm, and below, the requirements for wafer planarization precision have significantly increased, posing more stringent challenges to the hydrophilicity, polishing uniformity, and low-defect control capabilities of CMP polishing pads.

[0003] Currently, most commercial CMP polishing pads use polyurethane matrix and are prepared by DMF (dimethylformamide) wet phase transformation process. This material has inherent hydrophobic defects, and the contact angle of pure water is generally greater than 75°, which leads to the following problems: (1) Insufficient hydrophilicity and poor polishing fluid management: The strong hydrophobicity makes the polishing fluid spread unevenly on the pad surface, which easily forms local dry spots, leading to increased non-uniformity within / between MRR wafers and wafer edge effect, making it difficult to meet the precision requirements of advanced processes; at the same time, the weak liquid storage capacity leads to slow polishing fluid renewal and continuous decline in polishing efficiency; (2) Weak surface defect control: The hydrophobic interface easily adsorbs SiO2 / Al2O3 abrasive particles and debris in the polishing fluid, causing pore blockage and surface scaling, which forces the frequent use of diamond dressers, which increases costs and increases wafer surface particle defects due to increased residues, increasing cleaning difficulty and scrap risk. The existing hydrophilic modification schemes have the following fundamental defects: (1) Chemical grafting method: The process is complicated and damages the water resistance, mechanical strength and chemical resistance of polyurethane; (2) Surface coating method: The coating has weak bonding force with the substrate and quickly falls off and fails under mechanical trimming and high pressure washing; (3) Physical blending method: Hydrophilic nanofillers agglomerate due to van der Waals forces, resulting in poor dispersion and uneven modification. Hard agglomerates scratch the wafer surface, and the filler is easily lost during the process. Summary of the Invention

[0004] To overcome the technical problems of poor hydrophilicity, difficulty in balancing hydrophilicity and wear resistance, easy agglomeration of nanofillers, and incompatibility of modification processes with existing wet production lines in existing polyurethane CMP polishing pads, this invention provides a highly hydrophilic and wear-resistant CMP polishing pad, its preparation method, and its application. This invention prepares highly active carboxylate silsesquioxanes via a one-step alkaline hydrolysis method, and achieves nanoscale uniform dispersion of these carboxylate silsesquioxanes in a polyurethane matrix through a stepwise dispersion process. The cell structure during the wet phase transformation process is precisely controlled by acid-base oscillation impregnation, ultimately yielding a CMP polishing pad that combines long-lasting high hydrophilicity, high wear resistance, high polishing uniformity, and low defect rate. Furthermore, the preparation process is fully compatible with existing industrial production lines, meeting the high-precision CMP polishing requirements of semiconductor wafers.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] The first aspect of this invention provides a method for preparing a highly hydrophilic and wear-resistant CMP polishing pad, comprising the following steps:

[0007] The base fabric is soaked in an acid-base oscillating impregnating solution, squeezed, and left to stand. Then it is coated with a carboxylate silsesquioxane hybrid slurry, left to stand again, and then immersed in a coagulation bath to solidify and form a wet blank of the polishing pad.

[0008] The highly hydrophilic and wear-resistant CMP polishing pad is prepared by sequentially washing, drying and polishing the wet blank of the polishing pad;

[0009] The carboxylate silsesquioxane hybrid slurry includes polyurethane and carboxylate silsesquioxane powder.

[0010] The amount of the carboxylate silsesquioxane powder used is 0.5%-3% of the weight of the polyurethane;

[0011] The agglomeration size of the carboxylate silsesquioxane powder in the carboxylate silsesquioxane hybrid slurry is less than 100 micrometers;

[0012] The carboxylate silsesquioxane powder is obtained by hydrolyzing a cyanosiloxane monomer.

[0013] Furthermore, the cyanosiloxane monomer is selected from one or more of (2-cyanoethyl)triethoxysilane, (2-cyanoethyl)trimethoxysilane, (3-cyanopropyl)triethoxysilane, (3-cyanoisobutyl)triethoxysilane, (3-cyanopropyl)trimethoxysilane, and bis(3-cyanopropyl)dimethoxysilane.

[0014] Furthermore, the method for obtaining the carboxylate silsesquioxane powder includes the following steps: The cyanosiloxane monomer is continuously stirred in water, alkali is added, and the mixture is hydrolyzed at a constant temperature of 20-40°C for 10-15 hours to ensure complete hydrolysis of the cyano group into sodium carboxylate groups, with no unreacted cyano residue. Afterwards, the mixture is evaporated to dryness at below 70°C, ground, and sieved to obtain white carboxylate silsesquioxane powder. The hydrolysis reaction is mild and controllable, the product has a uniform carboxylate content, no side reactions, and good compatibility with polyurethane systems.

[0015] The molar ratio of the cyanosiloxane monomer, the alkali, and the water is 1:3-6:80-100.

[0016] Furthermore, the carboxylate silsesquioxane hybrid slurry also includes organic solvents and black paste;

[0017] The organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, methyl ethyl ketone, tetrahydrofuran, cyclohexanone, dioxane, and dimethyl sulfoxide;

[0018] The amount of organic solvent used is 35%-65% of the weight of the polyurethane; preferably 50%.

[0019] The amount of the black paste used is 6%-12% of the weight of the polyurethane; preferably 10%.

[0020] Preferably, the carboxylate silsesquioxane hybrid slurry comprises the following components in parts by weight:

[0021] 100 parts polyurethane, 0.5-3 parts carboxylate silsesquioxane powder, 50 parts organic solvent, 10 parts black paste.

[0022] Furthermore, the carboxylate silsesquioxane hybrid slurry is obtained using a stepwise dispersion method. Specifically, the organic solvent, the polyurethane, and the carboxylate silsesquioxane powder are pre-dispersed at a stirring rate greater than 500 rpm for 10-30 minutes to break up macroscopic agglomerations of the powder and achieve a primary uniform distribution of the filler in the polyurethane system. Then, ultrasonic dispersion at 200-800W for 10-30 minutes is performed to complete nano-deagglomeration. The cavitation effect of ultrasound generates high-frequency shear force to break up the microscopic nanoscale soft agglomerates of the carboxylate silsesquioxane solid powder, breaking them down from micron-level agglomerates to a nanoscale monodisperse state. Finally, post-dispersion at a stirring rate greater than 500 rpm for 10-30 minutes is performed to complete homogenization and degassing. This further homogenizes the nano-siloxanes after ultrasonic deagglomeration, ensuring a completely uniform distribution throughout the slurry system. It also eliminates a large number of microbubbles generated during the ultrasonic process, preventing pinholes and closed-cell defects during subsequent wet solidification.

[0023] Furthermore, the coating temperature of the carboxylate silsesquioxane hybrid slurry is 19-25℃, and the coating thickness is 0.8-2mm.

[0024] Furthermore, the acid-base oscillating immersion material is divided into acidic immersion material and alkaline immersion material. The acidic immersion material or the alkaline immersion material can be formed by stirring citric acid or ammonia water with N,N-dimethylformamide evenly, wherein the mass ratio of citric acid or ammonia water to N,N-dimethylformamide is 1-3:100.

[0025] The base fabric is a polyester nonwoven fabric with a basis weight of 100-150 g / m². 3 The thickness is 0.4-0.6 mm; the extrusion pressure after soaking the base fabric is 3-5 kg, and the standing time is 1-3 min. Through acid-base swing impregnation pretreatment, the protonation or deprotonation state of polyurethane molecules during the solidification process can be controlled, and the dual diffusion rate and phase transformation process of DMF and water can be precisely controlled, so that the cell distribution is more uniform, forming a three-dimensional pore structure with high open rate and good connectivity, avoiding closed pores, pinholes, and macropore defects.

[0026] Furthermore, the coagulation bath is a mixture of N,N-dimethylformamide and water, wherein the mass percentage of DMF is 20%-25%; the temperature of the coagulation bath is 19-25℃, and the coagulation time is 15-30 minutes. By controlling the coating and coagulation temperatures, the pore size, length, and open area ratio of the bubbles can be precisely controlled, forming a uniform and interconnected three-dimensional pore structure, which is suitable for the liquid storage and chip removal requirements of CMP polishing pads.

[0027] Furthermore, the water washing involves washing with room temperature clean water followed by pressing with 2-5 kg ​​pressure, repeated 40-80 times to thoroughly remove residual small molecule impurities such as DMF and sodium hydroxide; the drying temperature is 120-140℃ and the drying time is 10-30 min; the surface polishing involves polishing with 180-320 grit diamond sandpaper to a thickness of 0.1-0.2 mm, controlling the final product thickness tolerance to ≤±0.05 mm and the surface roughness Ra=5-15 μm, to meet the requirements of CMP polishing process.

[0028] A second aspect of the present invention provides a highly hydrophilic and wear-resistant CMP polishing pad prepared by the above-described method, which satisfies condition A below, and at least one of condition B below:

[0029] A condition:

[0030] Water contact angle less than 35°;

[0031] After friction with the H-22 grinding wheel at 1000 or 5000 revolutions under a 1kg load, the wear rate is less than 0.1%.

[0032] Condition B:

[0033] 24-hour water absorption rate is 18%-30%;

[0034] The open area ratio is at least 75%;

[0035] The mass loss rate after soaking in 10wt% NaOH solution for 24 hours is less than 0.9%;

[0036] The mass loss rate after soaking in 5wt% HCl solution for 24 hours is less than 0.8%.

[0037] The third aspect of this invention provides the application of the highly hydrophilic and wear-resistant CMP polishing pad prepared by the above-described method in chemical mechanical polishing, specifically for rough or fine polishing of 8-inch or 12-inch semiconductor wafers, wherein the semiconductor wafers are made of materials including silicon oxide, silicon nitride, copper, and tungsten, and can achieve high-precision, low-defect polishing requirements of 14nm and below.

[0038] Beneficial technical effects:

[0039] This invention prepares a silsesquioxane solid powder with a surface rich in highly active sodium carboxylate groups through one-step alkaline hydrolysis of cyanosiloxane monomers. The strongly hydrophilic carboxylate groups are anchored through a Si-O-Si inorganic framework and, combined with a stepwise dispersion process, achieve nanoscale uniform distribution in polyurethane. This fundamentally solves the problems of easy loss of hydrophilic modified groups and rapid decline in hydrophilicity in traditional methods. The polishing pad prepared by this invention has a pure water contact angle that is reduced from 75°-90° in pure polyurethane to less than 35°, and the water absorption rate is increased to more than 18.5% after 24 hours. This facilitates the rapid spread of polishing slurry on the polishing pad, completely solves the problem of dry spots at the polishing interface, significantly improves the storage, transport, and renewal capacity of the polishing slurry, and increases the stability of material removal rate by more than 50%, exhibiting long-lasting and stable high hydrophilicity.

[0040] Nanoscale uniform dispersion significantly reduces wafer surface defect rate: This invention disperses carboxylate silsesquioxane powder in polyurethane in steps. The step-dispersion process of pre-dispersion-ultrasonic dispersion-post-dispersion can completely break nanoscale agglomerates, achieving monodispersion of hydrophilic filler in polyurethane matrix, without the generation of micron-sized hard agglomerates, avoiding the risk of agglomerates scratching the wafer during polishing; at the same time, the uniformly distributed hydrophilic filler makes the hydrophilicity and hardness of the polishing pad completely uniform, and the pressure transmission is uniform during polishing, reducing the defect rate of wafer surface scratches, micro-pits and other defects, perfectly adapting to the low-defect polishing requirements of advanced processes.

[0041] The inorganic Si-O-Si framework of carboxylate silsesquioxane forms a strong interfacial bond with the polyurethane matrix, significantly improving hydrophilicity while effectively reducing the wear of the polishing pad. It also significantly enhances resistance to strong acids and alkalis, showing no surface cracking or performance degradation after immersion in 10wt% NaOH and 5wt% HCl solutions for 24 hours, perfectly adapting to the acid and alkali environments of CMP processes. Simultaneously, the Si-O-Si framework effectively improves the material's thermal conductivity, increases frictional heat dissipation efficiency, reduces the peak temperature at the polishing interface, minimizes wafer thermal deformation, extends the polishing pad's lifespan, and significantly reduces consumable costs in semiconductor manufacturing. This invention's polishing pad achieves synergistic optimization of hydrophilicity, wear resistance, and acid and alkali resistance, resulting in a significantly extended lifespan.

[0042] This invention achieves precise control over the dual diffusion rate and phase transformation process of DMF and water through coordinated regulation of process parameters, including acid-base oscillating impregnation pretreatment, coating with carboxylate-silsesquioxane hybrid slurry, and final wet solidification. Combined with the uniform nucleation effect brought about by the stepwise dispersion process of pre-dispersion-ultrasonic dispersion-post-dispersion, a three-dimensional pore structure with an open area ratio of ≥75%, concentrated pore size distribution, and excellent connectivity is formed. This effectively reduces the edge effect during polishing, and the non-uniformity of material removal rate within the wafer is <3%, fully adapting to the high-precision and stable polishing requirements of advanced semiconductor processes below 14nm. The polishing pad formation process of this invention provides precise control over the pore structure, significantly improving polishing accuracy and stability.

[0043] The preparation method of this invention is 100% compatible with existing wet production lines for polyurethane CMP polishing pads. No changes are required to the core production equipment and process routes. Performance improvement can be achieved simply through slurry blending modification and stepwise dispersion processes. The preparation process of carboxylate silsesquioxane powder is simple, the raw materials are readily available, and the cost is controllable. The stepwise dispersion process can be directly adapted to industrial reactor production. The product has strong batch stability, no additional production cost increase, strong process compatibility, and can quickly and directly achieve large-scale mass production. Detailed Implementation

[0044] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Unless otherwise specifically stated, the numerical values ​​set forth in these embodiments do not limit the scope of the invention. Techniques and methods known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques and methods should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that values ​​expressed, for example, as "within the range of ab" or "between the range of ab," do not include the endpoint values ​​a and b; values ​​expressed as "for ab," "is ab," or "ab" include the endpoint values ​​a and b.

[0046] Experimental methods not specified in the following examples are generally performed according to national standards; if there is no corresponding national standard, they are performed according to general standard requirements or general methods.

[0047] Pure water contact angle: The pure water contact angle on the surface of the polishing pad at 25℃ was measured using a contact angle measuring instrument. The average value of 5 test points was taken. The test standard refers to GB / T30693-2014.

[0048] Water absorption rate: Dry the polishing pad sample to constant weight, immerse it in deionized water at 25℃ for 24 hours, weigh the mass after water absorption, and calculate the water absorption rate. The test standard refers to GB / T1034-2008.

[0049] Abrasion resistance: The mass loss was tested after 1000 or 5000 revolutions using a Taber abrasion tester, H22 grinding wheel, and 1kg load.

[0050] Acid and alkali resistance: The samples were immersed in 10% NaOH aqueous solution and 5% HCl aqueous solution for 24 hours respectively. The mass loss rate before and after immersion was tested, and the surface morphology changes were observed. The mass loss rate was calculated as: (dry weight before immersion - dry weight after immersion) / dry weight before immersion × 100%.

[0051] Pore ​​structure: The cross-sectional morphology of the polishing pad was observed using a scanning electron microscope (SEM), and the porosity and pore size distribution were tested.

[0052] Filler dispersibility: The filler distribution in the cross-section of the polishing pad was observed using SEM, and the size and quantity of agglomerates were counted.

[0053] CMP polishing performance: Polishing tests were conducted using 8-inch silicon oxide wafers with a polishing pressure of 1.5 psi, a polishing disk rotation speed of 60 rpm, and a SiO2 abrasive alkaline polishing slurry. The tests included material removal rate (MRR), in-wafer non-uniformity (WIWNU), and surface defect rate (number of defects with a particle size ≥ 0.2 μm).

[0054] The polyurethane grades used below are as follows: XCW-P80R100g, a polyurethane resin for wet-process synthetic leather, with a solid content of 30wt%, supplied by Asahikawa Chemical (Suzhou) Co., Ltd. The black paste grade used below, 827-2, was purchased from Zhejiang Luoxing Chemical Co., Ltd.

[0055] (2-Cyanoethyl)triethoxysilane: Industrial grade, purity ≥98%, Jiangxi Chenguang New Materials Co., Ltd.; (2-Cyanoethyl)trimethoxysilane, 3-cyanopropyltriethoxysilane: Industrial grade, purity ≥98%, Hubei Xinlantian New Materials Co., Ltd.; Sodium hydroxide, citric acid, ammonia, DMF: All AR grade, Sinopharm Chemical Reagent Co., Ltd.

[0056] Example 1

[0057] A method for preparing a highly hydrophilic and wear-resistant CMP polishing pad, the specific steps of which are as follows:

[0058] Preparation of S1 carboxylate silsesquioxane powder:

[0059] 0.625 g of (2-cyanoethyl)triethoxysilane was added to 4.5 mL of 2 mol / L NaOH aqueous solution, wherein the molar ratio of (2-cyanoethyl)triethoxysilane, sodium hydroxide, and deionized water was 1:3:83. The mixture was stirred continuously in a constant temperature water bath at 40 °C for 15 h to ensure complete hydrolysis of the cyano group. The reaction solution was then transferred to an oven at 50 °C and heated to dryness. After grinding and passing through a 200-mesh sieve, a white powdery carboxylate silsesquioxane solid powder was obtained for later use.

[0060] Preparation of S2 carboxylate silsesquioxane hybrid slurry:

[0061] By weight, take 50 parts DMF, 100 parts polyurethane, 2 parts carboxylate silsesquioxane solid powder prepared in step S1, and 10 parts black paste. First, stir at 1000 rpm for 20 min to complete pre-dispersion, then ultrasonically disperse in a 500W water bath for 20 min to complete nano-de-agglomeration, and finally disperse and stir at 1000 rpm for 20 min to complete homogenization and degassing, to obtain a uniform and stable carboxylate silsesquioxane hybrid slurry for later use.

[0062] S3 base fabric pretreatment:

[0063] Add 2g of solid citric acid to 98g of DMF and stir until completely dissolved to obtain an acidic impregnating agent; immerse the polyester nonwoven fabric base in the acidic impregnating agent for 5 minutes, remove it and squeeze it under 4kg pressure, let it stand for 1 minute to complete the base fabric pretreatment.

[0064] S4 coating and wet solidification molding:

[0065] The carboxylate silsesquioxane hybrid slurry prepared in step S2 was kept at 23°C and uniformly coated onto the pretreated base fabric with a scraper. The coating thickness was 1.2 mm. After standing for 1 min, it was immediately immersed in a coagulation bath of 23°C and 22% by mass DMF aqueous solution. After coagulation for 20 min, the phase transformation molding was completed, and a wet blank of the polishing pad was obtained.

[0066] S5 Post-Processing:

[0067] The wet polishing pad blank was washed with room temperature water and then squeezed with 4 kg for 60 times to completely remove residual DMF. After that, it was placed in a 130℃ hot air circulating oven to dry for 20 minutes. Finally, the surface was polished with 240-grit diamond sandpaper to a thickness of 0.15 mm, and the final thickness was controlled to 1.0 mm to obtain a highly hydrophilic and wear-resistant CMP polishing pad.

[0068] Example 2

[0069] The preparation method of a highly hydrophilic and wear-resistant CMP polishing pad is the same as in Example 1, except that:

[0070] In S1, the cyanosiloxane monomer is (2-cyanoethyl)trimethoxysilane, the molar ratio of (2-cyanoethyl)trimethoxysilane, sodium hydroxide, and deionized water is 1:6:100, the hydrolysis temperature is 20℃, the stirring time is 12h, and the drying temperature is 60℃.

[0071] In S2, the amount of carboxylate silsesquioxane solid powder prepared in S1 is 3 parts;

[0072] In S3, the acid-base oscillating immersion material is an alkaline immersion material: 3g of ammonia water (5% by mass) is added to 97g of DMF and stirred until completely dissolved to obtain the alkaline immersion material; the extrusion pressure is 5kg;

[0073] In S4, the coating temperature (i.e., the isothermal temperature of the carboxylate silsesquioxane hybrid slurry) and the setting temperature are 25°C, the coating thickness of the carboxylate silsesquioxane hybrid slurry is 2.0 mm, the mass percentage of the DMF aqueous solution coagulation bath is 25%, and the setting time is 30 min.

[0074] In S5, the washing process is repeated 80 times, the drying temperature is 140℃, the drying time is 10 minutes, and the surface is polished to a thickness of 0.2mm with 320-grit diamond sandpaper, resulting in a final thickness of 1.5mm.

[0075] Example 3

[0076] The preparation method of a highly hydrophilic and wear-resistant CMP polishing pad is the same as in Example 1, except that:

[0077] In S1, the cyanosiloxane monomer selected is (3-cyanopropyl)triethoxysilane, and the molar ratio of (3-cyanopropyl)triethoxysilane, sodium hydroxide, and deionized water is 1:4:90. The hydrolysis temperature is 30℃ and the stirring time is 13h.

[0078] In S2, the amount of carboxylate silsesquioxane solid powder prepared in S1 added is 0.5 parts;

[0079] In S3, the mass ratio of citric acid to DMF in the acidic impregnation material is 1:100, and the extrusion pressure is 3 kg.

[0080] In S4, the coating temperature (i.e., the isothermal temperature of the carboxylate silsesquioxane hybrid slurry) and the setting temperature are 19℃, the coating thickness of the carboxylate silsesquioxane hybrid slurry is 0.8mm, the mass percentage of the DMF aqueous solution coagulation bath is 20%, and the setting time is 15min.

[0081] In S5, the washing process is repeated 40 times, the drying temperature is 120℃, the drying time is 30 minutes, and the surface is polished to a thickness of 0.1mm with 180-grit diamond sandpaper, resulting in a final thickness of 0.6mm.

[0082] Comparative Example 1

[0083] This comparative example is an unmodified pure polyurethane CMP polishing pad. The preparation steps are the same as in Example 1, except that S1 is not performed and S2 does not contain carboxylate silsesquioxane solid powder. All other process parameters are exactly the same.

[0084] Comparative Example 2

[0085] This comparative example is a polishing pad modified with a high addition amount. The preparation steps are the same as in Example 1, except that the amount of carboxylate silsesquioxane solid powder added in S2 is 6 parts, and the other process parameters are exactly the same.

[0086] Comparative Example 3

[0087] This comparative example is a modified polishing pad that did not use a stepwise dispersion process. The preparation steps are the same as in Example 1, except that in S2, only 1000 rpm pre-dispersion stirring for 60 min is used, and ultrasonic dispersion and post-dispersion secondary stirring are not performed. All other process parameters are exactly the same.

[0088] Comparative Example 4

[0089] This comparative example is a modified polishing pad prepared by only one step of ultrasonic dispersion. The preparation steps are the same as those in Example 1, except that in S2, only a 500W water bath is used for ultrasonic dispersion for 60 minutes. No pre-dispersion stirring or post-dispersion secondary stirring is performed. All other process parameters are exactly the same.

[0090] Comparative Example 5

[0091] This comparative example is a polishing pad without acid impregnation pretreatment. The preparation steps are the same as in Example 1, except that in S3, the base fabric is only soaked in pure DMF without adding citric acid, and the other process parameters are exactly the same.

[0092] Test case

[0093] The performance results of the polishing pads for each case are shown in Table 1.

[0094] Table 1. Performance of polishing pads in examples and comparative cases.

[0095]

[0096] The polishing pads from each case study were used for global planar polishing of all mainstream wafer materials (silicon dioxide and silicon nitride) in semiconductor manufacturing. The polishing parameters were as follows: polishing pressure 1.5 psi, polishing pad speed 60 rpm, wafer speed 55 rpm, and polishing slurry flow rate 150 mL / min. The polishing slurry was an alkaline SiO2 abrasive slurry (pH=10-12) with abrasive particle size of 30-100 nm. The results are shown in Table 2.

[0097] Table 2 Results of wafer CMP polishing performance

[0098]

[0099] The test results in Tables 1 and 2 show that:

[0100] The polishing pads prepared in Examples 1-3 of this invention have a pure water contact angle of less than 35° and a water absorption rate of over 18% after 24 hours. Compared with the pure polyurethane polishing pad of Comparative Example 1, the hydrophilicity of the polishing pads of this invention is improved by more than 200%. At the same time, the wear is reduced by more than 70%, and the mass loss rate after soaking in 10% NaOH and 5% HCl for 24 hours is less than 0.9%. There are no cracks or powdering on the surface, achieving synergistic optimization of hydrophilicity, wear resistance and acid and alkali corrosion resistance.

[0101] Comparative Example 3 did not employ a stepwise dispersion process, relying solely on mechanical stirring. This resulted in a large number of micron-sized agglomerates in the powder filler, significantly reducing its hydrophilicity and acid / alkali resistance. Surface cracking occurred after immersion in strong alkalis and acids, and the number of defects on the wafer surface increased significantly. Comparative Example 4 used only a one-step ultrasonic dispersion, which could deagglomerate the filler, but excessive air bubbles in the slurry led to an increase in the closed-cell rate and a decrease in the open-cell rate of the polishing pad, resulting in poor polishing uniformity and a certain degree of reduction in acid / alkali resistance. This fully verifies the necessity and irreplaceability of the stepwise dispersion process of this invention; all three steps are indispensable.

[0102] In Comparative Example 2, the amount of carboxylate silsesquioxane powder added was too high, resulting in severe agglomeration, which led to a decrease in the porosity of the polishing pad, a significant increase in wear, and a deterioration in polishing uniformity. At the same time, the acid and alkali resistance also showed a slight decrease.

[0103] Comparative Example 5 did not employ acid-base oscillating impregnation pretreatment, resulting in uneven pore structure and decreased porosity of the polishing pad, leading to poor polishing uniformity. This indicates that the base fabric pretreatment process plays a crucial role in accurately controlling the pore structure and improving polishing performance.

[0104] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a highly hydrophilic and wear-resistant CMP polishing pad, characterized in that, Includes the following steps: The base fabric is soaked in an acid-base oscillating impregnation solution, squeezed, and left to stand. Then it is coated with a carboxylate silsesquioxane hybrid slurry, left to stand again, and then immersed in a coagulation bath to solidify and form a wet blank of the polishing pad. The highly hydrophilic and wear-resistant CMP polishing pad is prepared by sequentially washing, drying and polishing the wet blank of the polishing pad; The carboxylate silsesquioxane hybrid slurry includes polyurethane and carboxylate silsesquioxane powder. The amount of the carboxylate silsesquioxane powder used is 0.5%-3% of the weight of the polyurethane; The agglomeration size of the carboxylate silsesquioxane powder in the carboxylate silsesquioxane hybrid slurry is less than 100 micrometers; The carboxylate silsesquioxane powder is obtained by hydrolyzing cyanosiloxane monomers.

2. The method for preparing a highly hydrophilic and wear-resistant CMP polishing pad according to claim 1, characterized in that, The cyanosiloxane monomer is selected from one or more of (2-cyanoethyl)triethoxysilane, (2-cyanoethyl)trimethoxysilane, (3-cyanopropyl)triethoxysilane, (3-acryloisobutyl)triethoxysilane, (3-cyanopropyl)trimethoxysilane, and bis(3-cyanopropyl)dimethoxysilane.

3. The method for preparing a highly hydrophilic and wear-resistant CMP polishing pad according to claim 2, characterized in that, The method for obtaining the carboxylate silsesquioxane powder includes the following steps: The cyanosiloxane monomer is continuously stirred in water, alkali is added, and it is hydrolyzed at a constant temperature of 20-40°C for 10-15 hours. After being evaporated to dryness at a temperature below 70°C, it is ground and sieved to obtain carboxylate silsesquioxane powder. The molar ratio of the cyanosiloxane monomer, the alkali, and the water is 1:3-6:80-100.

4. The method for preparing a highly hydrophilic and wear-resistant CMP polishing pad according to claim 1, characterized in that, The carboxylate silsesquioxane hybrid slurry also includes organic solvents and black paste; The organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, methyl ethyl ketone, tetrahydrofuran, cyclohexanone, dioxane, and dimethyl sulfoxide; The amount of the organic solvent used is 35%-65% of the weight of the polyurethane; The amount of the black paste used is 6%-12% of the weight of the polyurethane.

5. The method for preparing a highly hydrophilic and wear-resistant CMP polishing pad according to claim 4, characterized in that, The carboxylate silsesquioxane hybrid slurry is obtained by a stepwise dispersion method, specifically: the organic solvent, the polyurethane, and the carboxylate silsesquioxane powder are pre-dispersed at a stirring rate greater than 500 rpm for 10-30 min; then ultrasonically dispersed at 200-800 W for 10-30 min; and finally post-dispersed at a stirring rate greater than 500 rpm for 10-30 min. The coating temperature of the carboxylate silsesquioxane hybrid slurry is 19-25℃, and the coating thickness is 0.8-2mm.

6. A method for preparing a highly hydrophilic and wear-resistant CMP polishing pad according to any one of claims 1-5, characterized in that, The acid-base oscillating immersion material is divided into acidic immersion material and alkaline immersion material. The acidic immersion material or the alkaline immersion material can be formed by stirring citric acid or ammonia water with N,N-dimethylformamide evenly. The mass ratio of citric acid or ammonia water to N,N-dimethylformamide is 1-3:

100. The base fabric is a polyester nonwoven fabric with a weight of 100-150 g / m² and a thickness of 0.4-0.6 mm; the compression pressure of the base fabric after soaking is 3-5 kg, and the standing time is 1-3 min.

7. A method for preparing a highly hydrophilic and wear-resistant CMP polishing pad according to any one of claims 1-5, characterized in that, The coagulation bath is a mixture of N,N-dimethylformamide and water, wherein the mass percentage of DMF is 20%-25%; the temperature of the coagulation bath is 19-25℃ and the coagulation time is 15-30 min.

8. A method for preparing a highly hydrophilic and wear-resistant CMP polishing pad according to any one of claims 1-5, characterized in that, The washing process involves rinsing with room temperature clean water followed by pressing with 2-5 kg ​​of pressure, repeated 40-80 times to thoroughly remove residual small molecule impurities such as DMF and sodium hydroxide. The surface polishing is performed by polishing with 180-320 grit diamond sandpaper to a thickness of 0.1-0.2 mm, controlling the final product thickness tolerance to be ≤ ±0.05 mm, and the surface roughness Ra = 5-15 μm.

9. A highly hydrophilic and wear-resistant CMP polishing pad, characterized in that, The polishing pad prepared by the method according to any one of claims 1-8 satisfies condition A below, and also satisfies at least one of condition B below: A condition: The water contact angle is less than 35°; After friction with the H-22 grinding wheel at 1000 or 5000 revolutions under a 1kg load, the wear rate is less than 0.1%. Condition B: 24-hour water absorption rate is 18%-30%; The open area ratio is at least 75%; The mass loss rate after soaking in 10wt% NaOH solution for 24 hours is less than 0.9%; The mass loss rate after soaking in 5wt% HCl solution for 24 hours is less than 0.8%.

10. The application of a highly hydrophilic and wear-resistant CMP polishing pad in chemical mechanical polishing, characterized in that, The polishing pad is prepared by any one of the preparation methods described in claims 1-8, and is specifically applied to the rough polishing or fine polishing of 8-inch or 12-inch semiconductor wafers. The semiconductor wafers are made of materials including silicon oxide, silicon nitride, copper, and tungsten, and can achieve high-precision, low-defect polishing requirements of 14nm and below.

Images