A high porosity cmp polishing pad and method of making same

Abstract

The application discloses a high-porosity CMP polishing pad and a manufacturing method thereof, and belongs to the technical field of chemical mechanical polishing. The polishing pad is a four-layer composite structure, comprising a comb-shaped silicone modified polyurethane foam top gasket, a hot melt adhesive layer, a non-foaming thermoplastic polyurethane bottom gasket and a release tape. The manufacturing method comprises the following steps: preparing a polysiloxane chain extender, synthesizing a comb-shaped polyurethane, once water foaming, twice ammonium bicarbonate opening and post-processing compounding. The application improves wear resistance and resilience by enriching the surface of the comb-shaped silicone side chain, and solves the problems of porosity and mechanical property contradiction, poor wear resistance and permanent deformation of the buffer layer by combining with the twice opening and the four-layer rigid-flexible synergistic structure, so that high porosity, long service life and stable polishing effect are realized.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing (CMP) technology, specifically to a high-porosity CMP polishing pad and its manufacturing method. Background Technology

[0002] Chemical Mechanical Polishing (CMP) is currently the core process for achieving global planarization of wafer surfaces in integrated circuit manufacturing, and it is widely used in the ultra-precision processing of semiconductor substrate materials such as silicon wafers, silicon carbide, and sapphire. In the CMP process, the polishing pad, as a key consumable that comes into direct contact with the wafer, performs multiple functions, including delivering the polishing slurry, transferring mechanical load, removing reaction products, and maintaining the chemical environment of the polishing area. Its performance directly affects the material removal rate, planarization uniformity, and the level of surface defects on the wafer. Statistics show that the polishing pad accounts for approximately one-third of the total consumable cost of the CMP process, making it one of the core factors determining polishing efficiency and processing quality.

[0003] Polyurethane polishing pads have become the most widely used polishing pad material in the CMP field due to their excellent wear resistance, chemical stability, and controllable mechanical properties. To meet the storage and transport requirements of the polishing slurry during the polishing process, existing polyurethane polishing pads typically employ chemical or physical foaming techniques to form a porous structure within them. However, existing polyurethane foam polishing pads still have the following technical problems in practical applications: First, there is an inherent contradiction between porosity and mechanical properties. While increasing the amount of foaming agent can increase porosity, it often leads to uneven cell structure, excessively thin pore walls, or even collapse, significantly reducing the hardness and compressive strength of the polishing pad. This, in turn, affects the uniformity of pressure transmission and the planarization effect during the polishing process. Existing single-stage foaming processes struggle to achieve porosity exceeding 70% while ensuring sufficient mechanical properties.

[0004] Secondly, it suffers from insufficient wear resistance and resilience. During long-term use, the micro-peaks on the surface of traditional polyurethane polishing pads gradually wear down, and the micropores are easily clogged by polishing byproducts, leading to "glazing" of the pad surface and a continuous decline in polishing efficiency. Simultaneously, conventional polyurethane materials have poor resilience and are prone to permanent deformation after repeated pressure, affecting the uniform distribution of polishing pressure.

[0005] Third, the structural design of the polishing layer and the buffer layer lacks coordination. Although the existing double-layer composite polishing pads adopt the design concept of "hard on top and soft on the bottom", the molecular structure of the polishing layer itself has not been optimized for the foaming process, and the degree of phase separation between the hard and soft segments is difficult to control precisely. The buffer layer is mostly made of foamed polyurethane or non-woven fabric, which has large permanent compression deformation and obvious loss of resilience after long-term use.

[0006] Therefore, developing a CMP polishing pad that can balance high porosity, good mechanical properties, and wear resistance, and establishing a stable and controllable preparation method, is of great significance for improving the efficiency and quality of semiconductor planarization processing. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a high-porosity CMP polishing pad and its manufacturing method.

[0008] The technical solutions provided by the embodiments of the present invention are as follows: A method for manufacturing a high-porosity CMP polishing pad, characterized by comprising the following steps: S1. Preparation of polysiloxane chain extenders: S101. Diethanolamine and hexamethyldisilazane are heated and refluxed in anhydrous toluene at a molar ratio of 1:1.0-1.2. The byproduct ammonia gas escapes from the reaction system. After the reaction is completed, the mixture is distilled under reduced pressure and reacted with allyl bromide and potassium carbonate at a molar ratio of 1:1.0-1.2:1.3 at 60-80℃ for 4-6 hours. The nitrogen atom in hexamethyldisilazane has a lone pair of electrons, which nucleophilically attack the hydrogen atom on the hydroxyl group of diethanolamine. At the same time, the silicon atom combines with the oxygen atom of the hydroxyl group to form a trimethylsilyl ether bond. During the reaction, one molecule of hexamethyldisilazane can react with one molecule of diethanolamine. The byproduct is ammonia. As ammonia continuously escapes from the reaction system, it pushes the reaction equilibrium toward the product, making the hydroxyl protection reaction more complete and the yield higher. After the reaction, the solvent and excess reactants are removed by vacuum distillation to obtain bis(trimethylsiloxy)ethylamine. In this protected product, the active hydrogens of the two hydroxyl groups are replaced by trimethylsilyl groups, so that they will not interfere with the transformation of other functional groups in subsequent reactions. The second step is the alkylation reaction. The secondary amine group in bis(trimethylsiloxy)ethylamine undergoes a nucleophilic substitution reaction with allyl bromide under alkaline conditions. The reaction mechanism is as follows: potassium carbonate does not directly react with allyl bromide initially, but acts as an acid-binding agent to absorb the hydrogen bromide generated in the reaction, maintaining the alkaline environment of the reaction system. The secondary amine in bis(trimethylsiloxy)ethylamine acts as a nucleophile, retaining an active hydrogen atom on its nitrogen atom. Under alkaline conditions, the nucleophilicity of the nitrogen atom is enhanced, attacking the methylene carbon atom bonded to the bromine atom in allyl bromide, resulting in a bimolecular nucleophilic substitution reaction. The allyl group of allyl bromide... The basic structure makes the carbocation transition state relatively stable, which is conducive to the substitution reaction. During the reaction, the bromide ion leaves as a leaving group and combines with potassium carbonate to form potassium bromide precipitate, further promoting the reaction in the forward direction. After the reaction, the generated potassium bromide salt is removed by filtration, and N,N-bis(trimethylsiloxy)ethylallylamine is obtained by vacuum distillation. This product introduces a double bond group that can participate in the subsequent hydrosilylation reaction and a protected dihydroxyl group into the molecular structure, laying the foundation for subsequent grafting of polysiloxane segments and restoration of dihydroxyl functionality. The above reaction formula is as follows:

[0009] S102. Under nitrogen protection, tetramethyltetraphenylcyclotetrasiloxane is dissolved in a mixed solvent of anhydrous toluene and tetrahydrofuran. 1% n-butyllithium (by mass of tetramethyltetraphenylcyclotetrasiloxane) is added, and the mixture is reacted at room temperature for 3-4 hours. The mixture is then cooled to 0-5°C in an ice-water bath. 0.8-1.2% dimethylchlorosilane (by mass of tetramethyltetraphenylcyclotetrasiloxane) is added dropwise, and the reaction continues for 2 hours. After washing with water, drying, and vacuum distillation, a single-ended hydrogen-containing phenyl polysiloxane is obtained. This polysiloxane is then reacted with the product from S101 at a molar ratio of 1:1.2 in the presence of a platinum catalyst at 60-100°C for 4-8 hours via hydrosilylation. Finally, the mixture is stirred at room temperature for 2-4 hours in a methanol-acetic acid system at pH 4-5 to obtain a polysiloxane chain extender. The above process involves three consecutive reaction processes: first, the anionic ring-opening polymerization of cyclosiloxanes; then, the hydrosilylation reaction; and finally, the deprotection reaction of trimethylsilyl groups. (1) Anionic ring-opening polymerization: Under nitrogen protection, tetramethyltetraphenylcyclotetrasiloxane ring-opening polymerization was initiated using n-butyllithium (n-BuLi) as an initiator. As a strong base, n-butyllithium attacked the silicon atoms in the cyclosiloxane, causing the Si-O bond to break and forming an active siloxane anionic chain end. This active chain end continued to attack other cyclosiloxane monomers in the system, causing the chain segment to grow continuously and form a linear polysiloxane chain with a definite degree of polymerization. Subsequently, dimethylchlorosilane was added as a capping agent. The chlorine atom on its silicon atom was nucleophilically replaced by the oxygen anion of the active chain end, and a Si-O-Si bond was generated. At the same time, lithium chloride precipitate was generated, which terminated the polymerization reaction. Since the butyl end provided by n-butyllithium is an inert group, while dimethylchlorosilane introduces an active Si-H bond, the final product is a single-ended hydrogen-containing phenyl polysiloxane. (2) Hydrosilylation reaction: The single-ended hydrogen-containing phenyl polysiloxane obtained in the first step was subjected to hydrosilylation with the S101 product N,N-bis(trimethylsiloxy)ethylallylamine in the presence of a platinum catalyst. This reaction followed the Chalk-Harrod coordination addition mechanism: First, the zero-valent platinum catalyst coordinated with the allyl double bond to form a π-complex; simultaneously, the Si-H bond in the hydrogen-containing polysiloxane underwent oxidative addition to the platinum center, generating hydrides and silicide intermediates of Pt(IV); subsequently, the coordinated olefin was inserted into the Pt-H bond or the Pt-Si bond; finally, the target product was generated through reductive elimination, while the platinum catalyst was regenerated. This reaction connected the carbon-carbon double bond at the allyl end to the Si-H bond at the end of the polysiloxane to form a Si-C bond, allowing the polysiloxane segment to be connected to the protected amine structure through a stable chemical bond; (3) Deprotection reaction: In a methanol-acetic acid system at pH 4-5, methanol acts as a nucleophile, attacking the oxygen atom bonded to silicon, causing the Si-O bond to break. The trimethylsilyl group departs as a trimethylsilyl ether, and the previously protected hydroxyl groups are restored. The target product obtained after the reaction has the following structure: a phenyl polysiloxane segment with an inert butyl-terminated end and an N,N-dihydroxyethylamine structure connected to the other end via a stable propyl chain. The two primary hydroxyl groups are completely released and can be used for subsequent grafting reactions of the polyurethane backbone. The reaction formula for this process is as follows:

[0010] S2. Preparation of comb-shaped organosilicon-modified polyurethane: Diisocyanate and polycarbonate diol in a molar ratio of 1.3-1.6:1 were reacted at 70-85℃ for 2-5 hours to obtain a terminal isocyanate prepolymer. The temperature was then lowered to 60-70℃, and a polysiloxane chain extender was added for a grafting reaction for 2-4 hours. Then, a small molecule chain extender, 1,4-butanediol, and a catalyst, dibutyltin dilaurate, were added, and a chain extension reaction was carried out at 60-80℃ for 0.5-1 hours to obtain a comb-like organosilicon modified polyurethane. The -NCO group in diisocyanate is highly electrophilic due to the strong electrophilicity of its carbon atom, making it susceptible to nucleophilic attack from the -OH oxygen atom in polycarbonate diol, forming a urethane bond. By controlling the molar ratio of diisocyanate to polycarbonate diol to 1.3-1.6:1, ensuring an excess of -NCO in the reaction system, a prepolymer with both ends capped with -NCO is obtained. Subsequently, after cooling to 60-70℃, a single-terminated dihydroxyphenyl polysiloxane chain extender is added. The primary hydroxyl group at the end of this chain extender also acts as a nucleophile, undergoing an addition reaction with the -NCO at the prepolymer end group. Due to the low steric hindrance and high reactivity of the primary hydroxyl group, the reaction preferentially proceeds at this site, suspending the polysiloxane segment as a side chain on the polyurethane backbone. Finally, 1,4-butanediol is added... The reaction involves polycarbonate diol (BDO) and dibutyltin dilaurate (DBTDL). DBTDL acts as a catalyst, with its tin atoms coordinating with the oxygen atoms in the -NCO group to form a coordination complex. This further enhances the electrophilicity of the -NCO carbon atom, thereby accelerating the nucleophilic addition reaction. The two primary hydroxyl groups of BDO react with the terminal -NCO of the two prepolymer molecules, causing the molecular chain to elongate rapidly and form a high molecular weight polymer. In this process, the urethane segments generated by the reaction of BDO with diisocyanate have high polarity and high cohesive energy, and tend to aggregate to form hard segment microdomains. Meanwhile, the polycarbonate diol segments and the grafted polysiloxane side chains constitute soft segment microdomains. Due to thermodynamic incompatibility, the two undergo microphase separation, which endows polyurethane with good elasticity, hardness and wear resistance.

[0011] The polysiloxane in comb-shaped silicone-modified polyurethane is located on the side chain, which has a high degree of freedom and strong chain segment mobility, making it easy to form surface enrichment. It has the following functions: (1) Improved wear resistance: The side-chain organosilicon molecules have strong mobility and can significantly reduce the friction coefficient of the material. Studies have shown that adding 3.0% of side-chain organosilicon can increase the silicon content on the coating surface from 0 to 9.26%. (2) Improve hydrophobicity and antifouling properties: The organosilicon segments enriched on the surface can significantly improve the hydrophobicity of the material. Studies have shown that adding 15% by mass of side-chain organosilicon can make the water contact angle reach 110° and significantly improve the water resistance and antifouling properties of the material. (3) Improve chemical stability: The introduction of organosilicon can also enhance the thermal stability, weather resistance and chemical corrosion resistance of polymers, which is crucial for withstanding harsh environments such as CMP polishing fluid; S3, One-step foaming molding: Water, ammonium bicarbonate, polyether-modified silicone foaming agent and foaming catalyst are added to comb-shaped silicone-modified polyurethane. After mixing evenly, the mixture is poured into a mold, heated, and foamed for the first time. After curing, a foamed blank is obtained. When water is added to the comb-shaped silicone-modified polyurethane system, the hydroxyl groups in the water molecules act as nucleophiles, attacking the positively charged carbon atoms in the isocyanate groups (-NCO) remaining in the prepolymer or system, resulting in a nucleophilic addition reaction. This reaction first generates an unstable carbamic acid intermediate, which rapidly decomposes into an amine and carbon dioxide gas (CO2). The generated amine further reacts with another isocyanate group to form a substituted urea structure. The overall reaction formula is: 2R-NCO+H2O→R-NH-CO-NH-R+CO2↑ CO2 gas nucleates and expands in the viscous polyurethane system, forming an initial microporous structure. Simultaneously, the polyether-modified silicone foam stabilizer reduces the surface tension of the system, promoting uniform dispersion of bubbles and stabilizing the pore walls, preventing bubble coalescence or rupture. The foaming catalyst (dibutyltin dilaurate or triethylenediamine) accelerates the reaction rate of NCO with water, regulating the balance between foaming and gelation rates, thus fixing the bubbles as the system gradually solidifies, forming a foamed preform with a certain open and closed pore structure. At this stage, ammonium bicarbonate has not yet decomposed (the foaming temperature is usually controlled at 60-80℃, about 110℃ below its decomposition initiation temperature), and its main function is to provide an additional gas source in the subsequent secondary pore-opening step. S4. Secondary foaming and curing: The foamed blank is heated to 110-120℃ for a second foaming and kept at that temperature for 1-2 hours. At the same time, the post-curing and cross-linking of polyurethane is completed to obtain the top gasket blank. Ammonium bicarbonate begins to decompose at approximately 110°C, according to the following reaction: NH4HCO3→NH3↑+CO2↑+H2O↑ The ammonia, carbon dioxide, and water vapor produced during decomposition create additional gas pressure inside the pre-cured foam. These gases break through weak areas on the partially cured foam walls, allowing the originally closed micropores to connect and form an open-cell structure. This significantly improves the porosity and open-cell ratio of the polishing pad. Meanwhile, the residual isocyanate groups (-NCO) in the system continue to react under heating conditions: on the one hand, the residual -NCO reacts with -NH- in the urethane bond to form urethane; on the other hand, the residual -NCO reacts with -NH- in the urea bond to form biuret. These two crosslinking reactions form a three-dimensional network structure between the polyurethane molecular chains, improving the crosslinking density and mechanical properties of the polishing pad. The post-curing crosslinking and the gas produced by the decomposition of ammonium bicarbonate work together to maintain the mechanical integrity of the pore walls while opening the pores, ultimately resulting in a top gasket blank with high porosity and good mechanical properties. S5. Post-processing: The top gasket blank is sliced ​​to the target thickness, and grooves are machined on its upper surface. Then, a hot melt adhesive layer is applied to the lower surface of the top gasket. The bottom gasket is hot-pressed to the top gasket through the hot melt adhesive layer. Finally, a release tape is attached to the lower surface of the bottom gasket to obtain a high porosity CMP polishing pad. The top gasket blank is sliced ​​to the target thickness (2.5-3.0 mm) and grooves are machined. Then, a polyurethane hot melt adhesive layer is applied to the lower surface of the top gasket. This hot melt adhesive melts when heated to approximately 120°C, and the active groups such as hydroxyl (-OH) or amino (-NH2) groups in its molecular chain physically wet and chemically bond (such as urethane bonds, urea bonds, etc.) to the polar groups on the surfaces of the top and bottom gaskets (such as hydrogen bonds or a small number of covalent bonds). After cooling, it solidifies to form a strong adhesive interface. The bottom gasket (thermoplastic polyurethane film) is laminated with the top gasket by hot pressing. Under the conditions of pressure 0.5MPa, temperature 120℃ and time 30s, the hot melt adhesive layer flows fully and penetrates into the micropores on the surface of the two gaskets to achieve a stable interlayer bond. Finally, a PET release film coated with acrylic pressure-sensitive adhesive is laminated on the lower surface of the bottom gasket. The pressure-sensitive adhesive adheres to the bottom gasket through intermolecular forces (van der Waals forces). When in use, the polishing pad can be directly attached to the polishing pad of the CMP equipment by simply peeling off the release film. The functions of each layer in a CMP polishing pad are as follows: The top pad is the core functional layer of the polishing pad. It is made of comb-shaped silicone-modified polyurethane foam. Its high-porosity microporous structure is used to store and transport the polishing slurry, ensuring a uniform supply of slurry during the polishing process. At the same time, the grooves on its surface help to remove polishing debris and heat, and maintain the stability of the chemical environment in the polishing area. The hot melt adhesive layer serves as a fixing and connecting layer, firmly bonding the top and bottom pads together to prevent separation between layers during polishing. The bottom pad serves as a buffer layer, consisting of a non-foaming thermoplastic polyurethane film with high resilience and low compression set. Its function is to absorb the unevenness of polishing pressure and compensate for the microscopic unevenness between the wafer and the polishing pad, thereby improving the polishing uniformity and planarization effect. The release tape (including the release film) protects the adhesive backing of the bottom pad during transportation and storage. When in use, the release film is removed to expose the pressure-sensitive adhesive layer, making it easy to quickly and smoothly attach the polishing pad to the polishing pad of the CMP equipment.

[0012] Preferably, the number average molecular weight of the polysiloxane segments is 500-3000.

[0013] Preferably, the thickness of the top gasket is 2.5-3.0 mm, the Shore D hardness is 50-65, and the porosity is 70%-80%; the thickness of the bottom gasket is 0.4-0.9 mm.

[0014] Preferably, the upper surface of the top gasket is provided with a spiral or concentric circular groove, the groove having a depth of 0.8-1.2 mm and a width of 1-2 mm.

[0015] Preferably, the diisocyanate in S2 is isophorone diisocyanate (IPDI) or dicyclohexylmethane diisocyanate (HMDI). The number average molecular weight of polycarbonate diol is 1000-2000; The amount of polysiloxane chain extender added is 10-20% of the prepolymer mass; The molar amount of 1,4-butanediol is 4-8% of the prepolymer mass; The amount of dibutyltin dilaurate used is 0.03-0.1 wt% of the prepolymer mass.

[0016] Preferably, the mass ratio of comb-shaped silicone-modified polyurethane: water: ammonium bicarbonate: polyether-modified silicone foam stabilizer in S3 is 100:0.3-0.5:1-2:0.1-0.3; The foaming catalyst is dibutyltin dilaurate or triethylenediamine, and the amount of catalyst used is 0.02-0.05 wt% of the total mass of the reaction system. The temperature for the first foaming is 60-80℃, and the time is 20-40 minutes.

[0017] Preferably, the hot-pressing composite temperature in S5 is 120℃, the pressure is 0.5MPa, and the time is 30s; The release tape is a PET release film coated with acrylic pressure-sensitive adhesive.

[0018] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention uses comb-shaped organosilicon modified polyurethane as the polishing layer matrix, combined with the mechanism of polysiloxane side chain enrichment to the pore wall surface during the foaming and curing process, which solves the problem that the wear resistance and resilience of traditional polyurethane polishing pads decrease significantly after the porosity is increased. It achieves a significant reduction in friction coefficient, improvement in resilience and hydrolysis resistance without sacrificing high porosity, thus extending the service life of the polishing pad and improving polishing stability.

[0019] (2) The present invention adopts a four-layer composite structure design, namely, a top polishing layer composed of comb-shaped silicone modified polyurethane foam, a polyurethane hot melt adhesive layer, a non-foamed thermoplastic polyurethane (TPU) buffer layer and a release tape are stacked in sequence. Combined with the "rigid-flexible synergy" mechanism of the top rigid foam layer and the bottom high-resilience non-foamed layer, it solves the problems of large permanent deformation of the buffer layer under compression, fast elasticity decay and weak interlayer bonding in traditional double-layer polishing pads, and achieves uniform distribution of polishing pressure and stable planarization performance during long-term use.

[0020] (3) The present invention adopts a dual pore-forming method of water-induced primary chemical foaming to form basic micropores and ammonium bicarbonate decomposition at low temperature of 110-120℃ to perform secondary pore opening. Combined with the pore opening mechanism that the decomposition gas of ammonium bicarbonate only breaks through the weak area of ​​the pore wall without destroying the overall pore skeleton, the contradiction of single foaming is difficult to achieve both high porosity and good mechanical properties. A foam with a porosity of 70%-80% and intact pore walls and high compressive strength retention rate is obtained, which effectively ensures the uniform transmission of polishing pressure and wafer planarization effect.

[0021] (4) The present invention uses a polysiloxane chain extender constructed by hydrosilylation reaction of a single-ended hydrogen-containing phenyl polysiloxane and N,N-bis(trimethylsiloxy)ethylallylamine. Combined with the molecular design of phenyl side groups to improve compatibility with polyurethane matrix, it solves the technical problem of easy macroscopic phase separation and poor surface enrichment ability of organosilicon segments. This allows the side chains to be precisely suspended on the polyurethane main chain by chemical bonds, and significant surface modification effect can be achieved at low addition amount (10-20%), while avoiding the deterioration of mechanical properties. Attached Figure Description

[0022] Figure 1 This is a cross-sectional profile curve of the polishing pad groove in Embodiment 3 of the present invention; Figure 2 This is a comparison image of a standard polishing pad and a high-porosity polishing pad under an optical microscope. Detailed Implementation

[0023] The technical solutions of this invention are described below. It should also be noted that, to make the embodiments more detailed, the following embodiments are the best and preferred embodiments; those skilled in the art can also use other alternative methods to implement some well-known technologies.

[0024] In the following embodiments and comparative examples: The number average molecular weight of polycarbonate diol is 1500; The top gasket is 2.6 mm thick with a porosity of 70%-80%; the bottom gasket is 0.6 mm thick. The trench has a depth of 0.9 mm and a width of 1.5 mm; The release tape is a PET release film coated with acrylic pressure-sensitive adhesive.

[0025] Example 1: Method for manufacturing a high-porosity CMP polishing pad

[0026] S1. Preparation of polysiloxane chain extenders: S101. Diethanolamine and hexamethyldisilazane in a molar ratio of 1:1.1 are heated under reflux in anhydrous toluene. The byproduct ammonia gas escapes from the reaction system. After the reaction is completed, the mixture is distilled under reduced pressure and reacted with allyl bromide and potassium carbonate in a molar ratio of 1:1.1:1.3 at 60-80℃ for 4-6 hours. S102. Under nitrogen protection, tetramethyltetraphenylcyclotetrasiloxane was dissolved in a mixed solvent of anhydrous toluene and tetrahydrofuran. 1% n-butyllithium (by mass of tetramethyltetraphenylcyclotetrasiloxane) was added, and the mixture was reacted at room temperature for 3.5 h. The mixture was then cooled to 5 °C in an ice-water bath. 1% dimethylchlorosilane (by mass of tetramethyltetraphenylcyclotetrasiloxane) was added dropwise, and the reaction was continued for 2 h. After washing with water, drying, and vacuum distillation, a single-ended hydrogen-containing phenyl polysiloxane was obtained. This polysiloxane was then subjected to a hydrosilylation reaction with the product of S101 at a molar ratio of 1:1.2 in the presence of a platinum catalyst at 80 °C for 6 h. Finally, the mixture was stirred at room temperature for 3 h in a methanol-acetic acid system at pH 5 to obtain a polysiloxane chain extender. S2. Preparation of comb-shaped organosilicon-modified polyurethane: Isophorone diisocyanate and polycarbonate diol were reacted at 75°C for 3 hours to obtain a terminal isocyanate prepolymer. The temperature was lowered to 65°C, and 10% of the mass of polysiloxane chain extender was added to carry out a grafting reaction for 3 hours. Then, 6% of the mass of small molecule chain extender 1,4-butanediol and 0.08 wt% of catalyst dibutyltin dilaurate were added, and the chain extension reaction was carried out at 70°C for 1 hour to obtain comb-shaped organosilicon modified polyurethane. S3, One-step foaming molding: Water, ammonium bicarbonate, polyether-modified silicone foam stabilizer, and dibutyltin dilaurate foaming catalyst were added to comb-shaped silicone-modified polyurethane. After thorough mixing, the mixture was poured into a mold and heated to 70°C for the first foaming process, which lasted for 30 minutes. The resulting foamed preform was then cured. The mass ratio of comb-shaped silicone-modified polyurethane to water to ammonium bicarbonate to polyether-modified silicone foam stabilizer was 100:0.4:1.5:0.2, and the amount of dibutyltin dilaurate was 0.05 wt% of the total mass of the reaction system. S4. Secondary foaming and curing: The foamed blank is heated to 115℃ for a second foaming and kept at that temperature for 1.5 hours. At the same time, the post-curing and cross-linking of polyurethane is completed to obtain the top gasket blank. S5. Post-processing: The top gasket blank is sliced ​​to the target thickness, and grooves are machined on its upper surface. Then, a hot melt adhesive layer is applied to the lower surface of the top gasket. The bottom gasket is hot-pressed to the top gasket at 120℃ and 0.5MPa for 30s through the hot melt adhesive layer. Finally, a release tape is attached to the lower surface of the bottom gasket to obtain the high porosity CMP polishing pad.

[0027] Example 2: Method for manufacturing a high-porosity CMP polishing pad

[0028] S1. Preparation of polysiloxane chain extenders: S101. Diethanolamine and hexamethyldisilazane in a molar ratio of 1:1.1 are heated under reflux in anhydrous toluene. The byproduct ammonia gas escapes from the reaction system. After the reaction is completed, the mixture is distilled under reduced pressure and reacted with allyl bromide and potassium carbonate in a molar ratio of 1:1.1:1.3 at 60-80℃ for 4-6 hours. S102. Under nitrogen protection, tetramethyltetraphenylcyclotetrasiloxane was dissolved in a mixed solvent of anhydrous toluene and tetrahydrofuran. 1% n-butyllithium (by mass of tetramethyltetraphenylcyclotetrasiloxane) was added, and the mixture was reacted at room temperature for 3.5 h. The mixture was then cooled to 5 °C in an ice-water bath. 1% dimethylchlorosilane (by mass of tetramethyltetraphenylcyclotetrasiloxane) was added dropwise, and the reaction was continued for 2 h. After washing with water, drying, and vacuum distillation, a single-ended hydrogen-containing phenyl polysiloxane was obtained. This polysiloxane was then subjected to a hydrosilylation reaction with the product of S101 at a molar ratio of 1:1.2 in the presence of a platinum catalyst at 80 °C for 6 h. Finally, the mixture was stirred at room temperature for 3 h in a methanol-acetic acid system at pH 5 to obtain a polysiloxane chain extender. S2. Preparation of comb-shaped organosilicon-modified polyurethane: Isophorone diisocyanate and polycarbonate diol were reacted at 75°C for 3 hours to obtain a terminal isocyanate prepolymer. The temperature was lowered to 65°C, and 15% of polysiloxane chain extender by mass of the prepolymer was added for grafting reaction for 3 hours. Then, 6% of small molecule chain extender 1,4-butanediol and 0.08 wt% of catalyst dibutyltin dilaurate were added, and chain extension reaction was carried out at 70°C for 1 hour to obtain comb-shaped organosilicon modified polyurethane. S3, One-step foaming molding: Water, ammonium bicarbonate, polyether-modified silicone foam stabilizer, and dibutyltin dilaurate foaming catalyst were added to comb-shaped silicone-modified polyurethane. After thorough mixing, the mixture was poured into a mold and heated to 70°C for the first foaming process, which lasted for 30 minutes. The resulting foamed preform was then cured. The mass ratio of comb-shaped silicone-modified polyurethane to water to ammonium bicarbonate to polyether-modified silicone foam stabilizer was 100:0.4:1:0.2, and the amount of dibutyltin dilaurate was 0.05 wt% of the total mass of the reaction system. S4. Secondary foaming and curing: The foamed blank is heated to 115℃ for a second foaming and kept at that temperature for 1.5 hours. At the same time, the post-curing and cross-linking of polyurethane is completed to obtain the top gasket blank. S5. Post-processing: The top gasket blank is sliced ​​to the target thickness, and grooves are machined on its upper surface. Then, a hot melt adhesive layer is applied to the lower surface of the top gasket. The bottom gasket is hot-pressed to the top gasket at 120℃ and 0.5MPa for 30s through the hot melt adhesive layer. Finally, a release tape is attached to the lower surface of the bottom gasket to obtain the high porosity CMP polishing pad.

[0029] Example 3: Method for manufacturing a high-porosity CMP polishing pad

[0030] S1. Preparation of polysiloxane chain extenders: S101. Diethanolamine and hexamethyldisilazane in a molar ratio of 1:1.1 are heated under reflux in anhydrous toluene. The byproduct ammonia gas escapes from the reaction system. After the reaction is completed, the mixture is distilled under reduced pressure and reacted with allyl bromide and potassium carbonate in a molar ratio of 1:1.1:1.3 at 60-80℃ for 4-6 hours. S102. Under nitrogen protection, tetramethyltetraphenylcyclotetrasiloxane was dissolved in a mixed solvent of anhydrous toluene and tetrahydrofuran. 1% n-butyllithium (by mass of tetramethyltetraphenylcyclotetrasiloxane) was added, and the mixture was reacted at room temperature for 3.5 h. The mixture was then cooled to 5 °C in an ice-water bath. 1% dimethylchlorosilane (by mass of tetramethyltetraphenylcyclotetrasiloxane) was added dropwise, and the reaction was continued for 2 h. After washing with water, drying, and vacuum distillation, a single-ended hydrogen-containing phenyl polysiloxane was obtained. This polysiloxane was then subjected to a hydrosilylation reaction with the product of S101 at a molar ratio of 1:1.2 in the presence of a platinum catalyst at 80 °C for 6 h. Finally, the mixture was stirred at room temperature for 3 h in a methanol-acetic acid system at pH 5 to obtain a polysiloxane chain extender. S2. Preparation of comb-shaped organosilicon-modified polyurethane: Isophorone diisocyanate and polycarbonate diol were reacted at 75°C for 3 hours to obtain a terminal isocyanate prepolymer. The temperature was lowered to 65°C, and 15% of polysiloxane chain extender by mass of the prepolymer was added for grafting reaction for 3 hours. Then, 6% of small molecule chain extender 1,4-butanediol and 0.08 wt% of catalyst dibutyltin dilaurate were added, and chain extension reaction was carried out at 70°C for 1 hour to obtain comb-shaped organosilicon modified polyurethane. S3, One-step foaming molding: Water, ammonium bicarbonate, polyether-modified silicone foam stabilizer, and dibutyltin dilaurate foaming catalyst were added to comb-shaped silicone-modified polyurethane. After thorough mixing, the mixture was poured into a mold and heated to 70°C for the first foaming process, which lasted for 30 minutes. The resulting foamed preform was then cured. The mass ratio of comb-shaped silicone-modified polyurethane to water to ammonium bicarbonate to polyether-modified silicone foam stabilizer was 100:0.4:1.5:0.2, and the amount of dibutyltin dilaurate was 0.05 wt% of the total mass of the reaction system. S4. Secondary foaming and curing: The foamed blank is heated to 115℃ for a second foaming and kept at that temperature for 1.5 hours. At the same time, the post-curing and cross-linking of polyurethane is completed to obtain the top gasket blank. S5. Post-processing: The top gasket blank is sliced ​​to the target thickness, and grooves are machined on its upper surface. Then, a hot melt adhesive layer is applied to the lower surface of the top gasket. The bottom gasket is hot-pressed to the top gasket at 120℃ and 0.5MPa for 30s through the hot melt adhesive layer. Finally, a release tape is attached to the lower surface of the bottom gasket to obtain the high porosity CMP polishing pad.

[0031] Comparative Example 1: Compared with Example 3, in Comparative Example 1, no polysiloxane chain extender was prepared. Instead, dihydroxypropyl polysiloxane was used to replace the single-end chain extender of the present invention and attached to the main chain, while other conditions remained unchanged.

[0032] Comparative Example 2: Compared with Example 3, Comparative Example 2 did not involve organosilicon modification, and other conditions remained unchanged.

[0033] Comparative Example 3: Compared with Example 3, there was no secondary foaming in Comparative Example 3, and other conditions remained unchanged.

[0034] Comparative Example 4: Compared to Example 3, Comparative Example 4 used octamethylcyclotetrasiloxane instead of tetramethyltetraphenylcyclotetrasiloxane, while other conditions remained unchanged.

[0035] Comparative Example 5: Compared with Example 3, Comparative Example 5 had no bottom gasket and hot melt adhesive layer, while other conditions remained unchanged.

[0036] Performance testing: I. Basic Mechanical Property Testing Shore hardness test The test was conducted according to GB / T 531.1-2008 "Test method for indentation hardness of vulcanized rubber or thermoplastic rubber - Part 1: Shore hardness test (Shore hardness)". The top gasket foam was selected as the test object. A Shore D hardness tester was used. Five different locations were randomly selected on the sample surface for testing. The readings were recorded and the average value was calculated.

[0037] Compression strength test

[0038] The test was conducted in accordance with GB / T 8813-2020 "Determination of compressive properties of rigid foamed plastics". The test sample was a top-gap foam. The sample was compressed to 20% strain at a constant speed, the maximum compressive load was recorded, and the compressive strength was calculated to characterize the compressive strength and structural stability of high-porosity foam under polishing pressure.

[0039] Tensile strength and elongation at break test

[0040] The test was conducted in accordance with GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber". The top gasket foam was used as the sample. The sample was prepared with a dumbbell-shaped cutter and stretched at a speed of 50 mm / min until it broke. The tensile strength and elongation at break were recorded to evaluate the tensile strength and structural toughness of the foam during processing and use.

[0041] Apparent density test

[0042] According to GB / T 6343-2009 "Determination of Apparent Density of Foamed Plastics and Rubber", the mass and volume of the top gasket foam sample were measured, and the apparent density was calculated as the basic parameter for porosity calculation.

[0043] Porosity test

[0044] The theoretical calculation formula is: P = (1 - ρ / ρ0) × 100%, where ρ is the apparent density of the sample, and ρ0 is taken as the density of the polyurethane matrix, which is 1.20 g / cm³. 3 The top gasket foam was used as the test object.

[0045] II. Wear Resistance Test

[0046] DIN abrasion test

[0047] According to GB / T 9867-2008 "Determination of abrasion resistance of vulcanized rubber or thermoplastic rubber (rotary roller abrasion mill method)", the top gasket foam was used as the sample. The mass loss of the sample under standard abrasion conditions was tested using a rotary roller abrasion mill to evaluate the effect of comb-shaped silicone side chains on improving abrasion resistance.

[0048] Friction coefficient test

[0049] According to GB / T 10006-2021 "Determination of the coefficient of friction of plastic films and sheets", the surface of the top gasket foam is used as the test object, and the dynamic and static coefficients of friction are tested by the horizontal drag method to characterize the effect of organosilicon side chains on the friction characteristics of the polishing pad surface.

[0050] III. Chemical Stability Test

[0051] Alkali resistance test

[0052] The top gasket foam was prepared into a standard sample, which was then immersed in a KOH aqueous solution (containing 1 wt% H2O2) with pH=10 and kept at a constant temperature of 80℃ for 72 hours. After being taken out, it was washed, dried and weighed. The mass change rate was calculated according to the formula: mass change rate (%) = (mass after immersion - mass before immersion) / mass before immersion × 100%. This was used to verify the effect of the comb-shaped organosilicon structure on improving the alkali resistance of the material.

[0053] Acid resistance test

[0054] The top gasket foam sample was immersed in an HCl solution with pH=3 and kept at a constant temperature of 80℃ for 72 hours. After drying, it was weighed and the mass change rate was calculated according to the above formula to evaluate the effect of the comb structure on improving acid resistance.

[0055] Yellowing resistance test

[0056] The top gasket foam sample was placed in a UV aging test chamber and continuously irradiated at 60℃ for 72 hours using a UV-A 340nm light source. The color change of the sample surface was observed and the hardness retention rate was tested to verify the yellowing resistance and aging resistance of the aliphatic IPDI system.

[0057] IV. Polishing Performance Test

[0058] Material Removal Rate (MRR) Test

[0059] Using standard CMP polishing technology and a composite four-layer polishing pad as the test object, K9 glass or SiC wafers were precisely weighed before and after polishing, and the material removal rate was calculated according to the formula: MRR = Δm × 10 7 / (ρπr 2 t), where Δm is the workpiece mass difference, ρ is the workpiece density, r is the workpiece radius, and t is the polishing time, used to evaluate polishing efficiency.

[0060] V. Interlayer Bonding Performance Test

[0061] Compression rebound rate test

[0062] The composite polishing pad was placed in a standard testing device and subjected to 1000 cycles of compression under a constant pressure of 27.58 kPa. The thickness of the sample before compression and after rebound was tested, and the compression rebound rate was calculated according to the formula: Compression rebound rate (%) = Thickness after rebound / Initial thickness × 100%. This is used to evaluate the thickness stability of the composite structure under long-term dynamic load and the rebound performance of the bottom TPU film buffer layer.

[0063] The above performance test data are shown in Tables 1 and 2.

[0064] Table 1 Basic Mechanical Performance Data

[0065] Table 2. Data on wear resistance, polishability, and resilience

[0066] Table 3 Chemical stability data

[0067] Figure 1 The groove cross-sectional profile curve of the polishing pad in Embodiment 3 of the present invention, measured by a profilometer, shows a groove depth of approximately 0.9 mm. The groove sidewalls are steep and the bottom is flat, indicating good machining accuracy and effective storage of polishing fluid and grinding debris. The surface height outside the groove (platform area) is stable at around 0 μm, indicating good surface flatness of the polishing pad and no obvious warping.

[0068] Figure 2 This is an optical microscope comparison of the pore structure of a standard polishing pad and the high-porosity polishing pad of this invention. The top image shows the standard polishing pad, which has uneven pore size distribution and low porosity; the bottom image shows the high-porosity polishing pad of this invention, which has more uniform pore distribution and significantly improved porosity.

[0069] Data Analysis: As can be seen from the data in Tables 1 to 3, the performance differences between the embodiments of the present invention and the comparative examples have clear regularities. These regularities can be reasonably explained from the structure-performance relationship of polyurethane foam materials and the surface chemical behavior of organosilicon side chains.

[0070] First, as the amount of organosilicon chain extender increased from 10% to 15% and the amount of ammonium bicarbonate increased from 1 part to 1.5 parts in Examples 1, 2, and 3, the apparent density of the top gasket increased from 0.31 g / cm³. 3 Reduced to 0.27 g / cm³ 3 The porosity increased from 74.2% to 77.5%, the Shore D hardness decreased from 51.2 to 48.1, and the compressive strength decreased from 2.85 MPa to 2.43 MPa. This trend is consistent with the pattern observed in Chen Minxuan's "Preparation, Structure and Performance Study of Polyurethane Foamed Polishing Pads": the gas generated by the decomposition of the secondary foaming agent (ammonium bicarbonate) breaks through the cell walls to form a connected open-cell structure, resulting in a decrease in density and an increase in porosity; the relative reduction in the content of hard segments leads to a decrease in crosslinking density, and the hardness and compressive strength decrease accordingly. Comparative Example 2 (without organosilicon modification) has the highest density and the lowest porosity because it did not introduce flexible organosilicon side chains and did not undergo secondary foaming, thus having the highest hardness and compressive strength; Comparative Example 3 (without secondary foaming), although the organosilicon content is the same as in Example 3, relies solely on water foaming to form a closed-cell structure, resulting in a higher density and lower porosity, further confirming the effectiveness of secondary foaming in reducing density and increasing porosity.

[0071] Regarding tensile strength and elongation at break, the tensile strength of Examples 1 to 3 decreased slightly with increasing silicone content (2.65 → 2.38 MPa), while the elongation at break increased (116% → 126%). Comparative Example 2 showed the highest tensile strength (3.18 MPa), but the tensile strength of Comparative Example 1 (block silicone) (2.21 MPa) was lower than all other examples. Grafted (i.e., side-grafted) silicone had less impact on the mechanical properties of polyurethane at the same content than block-modified silicone because the side chains have greater freedom and relatively limited interference with hard segment hydrogen bonds; however, the inherently low cohesive energy of silicone segments still resulted in a slight decrease in tensile strength compared to pure polyurethane, while its flexible segments imparted a higher elongation at break to the material.

[0072] The wear resistance and coefficient of friction data reflect the surface enrichment effect of the silicone side chains. The DIN wear of Examples 1 to 3 ranges from 95 mm. 3 Reduced to 71 mm 3 The static friction coefficient decreased from 0.42 to 0.35; the wear in Comparative Example 2 was as high as 168 mm. 3The coefficient of friction is 0.62. Tan Zhuyan et al., in their paper "Synthesis and Characterization of Polyurethane Dispersions Containing Polysiloxane Side Chains," confirmed using XPS that the polysiloxane side chains extend and enrich towards the surface during film formation, resulting in a surface silicon content far exceeding the theoretical value. This self-lubricating layer reduces adhesive wear and frictional resistance on the polishing pad surface. Furthermore, higher silicone content and more complete surface enrichment lead to better wear resistance and a lower coefficient of friction. The wear and coefficient of friction in Comparative Example 1 are between those of Examples 1 and 2, but higher than those of Example 3, indicating that the chain movement of block silicone is restricted, and its surface migration ability is weaker than that of side-linked branches.

[0073] Chemical stability data showed that the alkali resistance mass loss rate of Examples 1 to 3 improved from -2.11% to -1.62%, acid resistance improved from -1.65% to -1.27%, hardness retention increased from 94% to 96%, and yellowing resistance reached level 5; Comparative Example 2 was the worst (-3.58%, -2.86%, 85%, level 3-4). The polysiloxane backbone in organosilicon has excellent hydrophobicity, which can effectively shield water molecules and OH groups. - Hydrolytic attack on polyurethane ester and urea groups. Higher content of organosilicon in the side chains results in a denser hydrophobic barrier on the pore wall surface, inhibiting the hydrolysis reaction and thus reducing mass loss and increasing hardness retention. Improved yellowing resistance is attributed to the use of aliphatic IPDI instead of aromatic MDI, which avoids UV-induced quinone chromophore formation at the molecular structure level. The surface enrichment of organosilicon side chains further reduces the contact between UV light and the polyurethane backbone.

[0074] Regarding material removal rate (MRR), Example 3 achieved an MRR of 145 nm / min, while Comparative Example 3 (without secondary foaming) only achieved 85 nm / min. Chen Minxuan's research clearly indicates that the secondary foaming process with added ammonium bicarbonate can increase porosity by 7.2% and MRR by 47.8%. The gas generated by the decomposition of ammonium bicarbonate at 115°C breaks through the closed-pore walls to form an open-pore structure. The increased open-pore ratio enhances the slurry storage capacity and slurry delivery efficiency of the polishing pad, resulting in more thorough and uniform contact between the abrasive grains and the wafer, thus significantly improving the MRR. Comparative Example 2 achieved the highest MRR (158 nm / min), but due to its excessively high hardness and lack of silicone lubrication, it exacerbated surface scratches on the wafer, resulting in an overall polishing quality inferior to the Example 3.

[0075] Finally, the compression rebound data showed that the rebound rates of the examples with composite structures (including a TPU bottom buffer layer) and most comparative examples were higher than 95%, while the rebound rate of Comparative Example 5 (single-layer structure) was slightly lower (95.0%). This verifies the high resilience of the bottom non-foamed TPU film as a buffer layer. Its synergistic deformation with the top foamed layer after hot melt adhesive bonding effectively improves compression set during long-term use, outperforming traditional foamed buffer layers.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-porosity CMP polishing pad, characterized in that, The polishing pad has a four-layer composite structure, which includes, from top to bottom: a top pad, a hot melt adhesive layer, a bottom pad, and a release tape; The top gasket is made of comb-shaped silicone-modified polyurethane foam, which is formed by chemical foaming of comb-shaped silicone-modified polyurethane with a foaming agent to form a microporous structure, and then undergoes secondary pore opening through thermal decomposition of ammonium bicarbonate. The bottom pad is a thermoplastic polyurethane film; The hot melt adhesive layer is fixedly connected to the top gasket and the bottom gasket respectively; The release tape is peelably attached to the lower surface of the bottom pad.

2. The high-porosity CMP polishing pad according to claim 1, characterized in that, The molecular structure of the comb-shaped organosilicon-modified polyurethane includes: a polyurethane backbone; and side chains connected to the polyurethane backbone by chemical bonds, wherein the side chains are polysiloxane segments containing phenyl groups, and the ends of the side chains contain two hydroxyl groups. The chemical structural formula is as follows: The number average molecular weight of polysiloxane segments is 500-3000.

3. The high-porosity CMP polishing pad according to claim 1, characterized in that, The thickness of the top gasket is 2.5-3.0 mm, the Shore D hardness is 50-65, and the porosity is 70%-80%; the thickness of the bottom gasket is 0.4-0.9 mm.

4. The high-porosity CMP polishing pad according to claim 1, characterized in that, The upper surface of the top gasket is provided with a spiral or concentric circular groove, the groove having a depth of 0.8-1.2 mm and a width of 1-2 mm.

5. A method for manufacturing a high-porosity CMP polishing pad as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Preparation of polysiloxane chain extenders: S101. Diethanolamine and hexamethyldisilazane are heated and refluxed in anhydrous toluene at a molar ratio of 1:1.0-1.

2. The byproduct ammonia gas escapes from the reaction system. After the reaction is completed, the mixture is distilled under reduced pressure and reacted with allyl bromide and potassium carbonate at a molar ratio of 1:1.0-1.2:1.3 at 60-80℃ for 4-6 hours. S102. Under nitrogen protection, tetramethyltetraphenylcyclotetrasiloxane is dissolved in a mixed solvent of anhydrous toluene and tetrahydrofuran. 1% n-butyllithium (by mass of tetramethyltetraphenylcyclotetrasiloxane) is added, and the mixture is reacted at room temperature for 3-4 hours. The mixture is then cooled to 0-5°C in an ice-water bath. 0.8-1.2% dimethylchlorosilane (by mass of tetramethyltetraphenylcyclotetrasiloxane) is added dropwise, and the reaction continues for 2 hours. After washing with water, drying, and vacuum distillation, a single-ended hydrogen-containing phenyl polysiloxane is obtained. This polysiloxane is then reacted with the product from S101 at a molar ratio of 1:1.2 in the presence of a platinum catalyst at 60-100°C for 4-8 hours via hydrosilylation. Finally, the mixture is stirred at room temperature for 2-4 hours in a methanol-acetic acid system at pH 4-5 to obtain a polysiloxane chain extender. S2. Preparation of comb-shaped organosilicon-modified polyurethane: Diisocyanate and polycarbonate diol in a molar ratio of 1.3-1.6:1 were reacted at 70-85℃ for 2-5 hours to obtain a terminal isocyanate prepolymer. The temperature was then lowered to 60-70℃, and a polysiloxane chain extender was added for a grafting reaction for 2-4 hours. Then, a small molecule chain extender, 1,4-butanediol, and a catalyst, dibutyltin dilaurate, were added, and a chain extension reaction was carried out at 60-80℃ for 0.5-1 hours to obtain a comb-like organosilicon modified polyurethane. S3, One-step foaming molding: Water, ammonium bicarbonate, polyether-modified silicone foaming agent and foaming catalyst are added to comb-shaped silicone-modified polyurethane. After mixing evenly, the mixture is poured into a mold, heated, and foamed for the first time. After curing, a foamed blank is obtained. S4. Secondary foaming and curing: The foamed blank is heated to 110-120℃ for a second foaming and kept at that temperature for 1-2 hours. At the same time, the post-curing and cross-linking of polyurethane is completed to obtain the top gasket blank. S5. Post-processing: The top gasket blank is sliced ​​to the target thickness, and grooves are machined on its upper surface. Then, a hot melt adhesive layer is applied to the lower surface of the top gasket. The bottom gasket is hot-pressed to the top gasket through the hot melt adhesive layer. Finally, a release tape is attached to the lower surface of the bottom gasket to obtain a high porosity CMP polishing pad.

6. The method for manufacturing a high-porosity CMP polishing pad according to claim 5, characterized in that, In S2: The diisocyanate is isophorone diisocyanate (IPDI) or dicyclohexylmethane diisocyanate (HMDI). The number-average molecular weight of the polycarbonate diol is 1000-2000; The amount of the polysiloxane chain extender added is 10-20% of the mass of the prepolymer; The amount of 1,4-butanediol added is 4-8% of the prepolymer mass; The amount of dibutyltin dilaurate used is 0.03-0.1 wt% of the prepolymer mass.

7. The method for manufacturing a high-porosity CMP polishing pad according to claim 5, characterized in that, The mass ratio of comb-shaped silicone-modified polyurethane, water, ammonium bicarbonate, and polyether-modified silicone foam stabilizer in S3 is 100:0.3-0.5:1-2:0.1-0.

3. The foaming catalyst is dibutyltin dilaurate or triethylenediamine, and the amount of catalyst used is 0.02-0.05 wt% of the total mass of the reaction system. The temperature for the first foaming is 60-80℃, and the time is 20-40 minutes.

8. The method for manufacturing a high-porosity CMP polishing pad according to claim 6, characterized in that, The hot-pressing composite in S5 is performed at a temperature of 120°C, a pressure of 0.5 MPa, and a time of 30 seconds. The release tape is a PET release film coated with acrylic pressure-sensitive adhesive.

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