A white pad for rough polishing of wafer surface and a manufacturing method thereof

Abstract

The present application relates to the technical field of polishing pad, and discloses a white pad for rough polishing of wafer surface and a manufacturing method, which solves the problem of polishing precision decline caused by aging and wear in the prior art. A double-layer composite structure is adopted, the surface layer is a closed-cell foam structure, is used for storing polishing liquid and realizing flexible grinding, and the material comprises polyether polyurethane resin, micron-sized wear-resistant filler and anti-aging component; the bottom layer is an open-cell foam structure, is responsible for efficient chip removal and heat dissipation, and comprises polyether polyurethane resin, heat-conducting filler and structural reinforcing fiber. The manufacturing process successively passes through raw material pretreatment, layered extrusion sheet, three-roll calendering compounding, edge strengthening coating, plasma surface treatment and cutting processing. Through double-layer functional partition design and material system optimization, the present application significantly improves the wear resistance, aging resistance and heat conductivity of the white pad, can adapt to conventional and special rough polishing conditions, prolongs the service life and guarantees the polishing precision, and is suitable for industrial application.

Description

Technical Field

[0001] This invention relates to the field of polishing pad technology, and more particularly to a white pad for rough polishing of wafer surfaces and a method for manufacturing it. Background Technology

[0002] In the chemical mechanical polishing (CMP) process of semiconductor wafers, the rough polishing pad, as a core consumable, plays a crucial role in storing polishing slurry, transferring mechanical load, and removing reaction residues. Its performance directly affects polishing accuracy and production line efficiency. With the upgrading of semiconductor process nodes to 5nm and below, the requirements for wafer surface flatness are becoming increasingly stringent. The rough polishing process must simultaneously meet the dual objectives of high material removal rate and low surface damage. Currently, the industry generally uses polyurethane foam substrates, employing surface trenches and porous structures to achieve polishing slurry distribution and chip removal. However, under the high-load, highly corrosive, and wide-temperature-range rough polishing conditions, traditional materials face challenges in terms of wear resistance, aging resistance, and dynamic adaptability. To meet the dual demands of advanced processes for polishing accuracy and cost control, the industry urgently needs to develop a new generation of white pad products that combine high wear resistance, long lifespan, and intelligent response characteristics. Through material modification and structural innovation, dynamic control of the polishing slurry and adaptive operation can be achieved, driving the improvement of precision and the localization of semiconductor manufacturing processes.

[0003] The prior art, CN116460734A, discloses a polyurethane composite polishing pad and its preparation method. First, 10-20 parts by weight of polyurethane resin, 70-95 parts by weight of solvent, 3-5 parts by weight of abrasive, and 5-10 parts by weight of reinforcing components are added to a mixer and stirred for 0.5-1 hours to obtain an impregnation solution. At room temperature, the substrate is impregnated in the impregnation solution, and then placed in water for pre-coagulation for 10-30 minutes. After pre-coagulation, it is dried. Addressing the issues of poor thermal conductivity and wear resistance in composite polishing pads, the prior art provides a polyurethane composite polishing pad using non-woven or woven fabric as the substrate. By introducing reinforcing components into the polyurethane impregnation solution, the thermal conductivity and wear resistance of the polishing pad are improved without reducing its water permeability, thereby increasing the lifespan of the polishing pad. The prior art publication number CN117020933A also discloses a white pad for semiconductor polishing and its manufacturing process, including a nanofiber sandwich section, which is disposed in the middle of the interior of the white pad body, a circular connecting section is disposed on the upper outer side of the white pad body, a homogeneous main body layer is disposed on the lower end face of the nanofiber sandwich section, and a high flatness polishing section is disposed on the lower end of the homogeneous main body layer; the high flatness polishing section is characterized by comprising a polyurethane polishing base layer and a filling layer, wherein the polyurethane polishing base layer comprises 120-150 parts of modified polyurethane and 30-45 parts of polyurethane adhesive; the modified polyurethane preparation process includes the following steps: Step 1: Polytetrahydrofuran diol is placed in a reaction vessel, and toluene-2 ​​is added dropwise. Step 1: Add 4-diisocyanate and the accelerator dibutyltin dilaurate; add 8% N,N-dimethylformamide solution of 1,2,4-benzenetricarboxylic anhydride and react for 3 hours to obtain polyurethane oligomer; Step 2: Potassium tert-butoxide, methylsilanetriol, and methyl 3-dodecyl thiopropionate are heated to react and obtain intermediate 1; Step 3: Add the polyurethane oligomer to intermediate 1 and stir continuously at 100°C for 2 hours to obtain modified polyurethane oligomer; Step 4: Continue stirring and cooling the modified polyurethane oligomer to 35-45°C, add the active compound, cool to room temperature, add the polymerization inhibitor and free radical initiator, and continue stirring for 15-30 minutes to obtain modified polyurethane.

[0004] Regarding the above-mentioned and existing related technologies, the inventors believe that the following defects often exist:

[0005] 1. Existing technologies mostly employ polyurethane resin composites with non-woven or woven fabric substrates. Although reinforcing components are introduced to improve wear resistance, material wear is still relatively rapid under high-load conditions. The single-layer homogeneous structure causes the distribution of polishing fluid and chip removal function to rely on surface grooves. After long-term use, groove wear leads to a decrease in chip removal efficiency and an increased risk of surface damage. In addition, although the impregnation fluid mixing process is simple, the uniformity of functional filler dispersion is difficult to control, resulting in uneven local wear.

[0006] 2. Existing technologies do not add or use only a small amount of antioxidants, making the polyurethane molecular chains prone to breakage under strong oxidizing environments, leading to decreased hardness and tensile strength. The single-layer structure lacks an anti-aging functional layer, resulting in material embrittlement and reduced polishing consistency after long-term use. The impregnation solution mixing process has not optimized the dispersion of anti-aging components, leading to uneven aging in certain areas.

[0007] 3. Polyurethane resin itself has a low thermal conductivity, and existing technologies do not specifically introduce high thermal conductivity fillers, so heat dissipation relies on the heat conduction of the substrate itself. The single-layer structure lacks a pore gradient design, making it difficult for the frictional heat generated during polishing to be quickly transferred to the bottom layer for dissipation, leading to localized overheating and accelerating material aging.

[0008] 4. Existing technologies do not use corrosion-resistant fillers, and polyurethane is easily hydrolyzed in strongly alkaline polishing solutions, resulting in a high quality loss rate. The single-layer structure lacks a barrier layer, allowing corrosive media to easily penetrate into the substrate, leading to performance degradation. Furthermore, the surface treatment process has not been optimized for corrosion resistance, requiring additional protective coatings. Summary of the Invention

[0009] The technical problem to be solved by the present invention is that the existing technology has the disadvantage of reduced polishing accuracy due to aging and wear. To address this, we propose a white pad for rough polishing of wafer surfaces and a method for its fabrication.

[0010] To achieve the above objectives, this application adopts the following technical solution: a white pad for rough polishing of wafer surfaces and its manufacturing method, comprising a surface layer and a bottom layer. The surface layer focuses on polishing slurry storage and flexible grinding. The surface layer preparation materials, by weight ratio, include 55-60 parts of polyether-type polyurethane resin, 12-18 parts of micron-sized zirconium oxide, 15-18 parts of micron-sized silicon nitride, 4-8 parts of hexagonal boron nitride, 1-2 parts of graphene oxide, 4-6 parts of fluorosilane-modified silica, 7-10 parts of high molecular weight hindered amine 622, and 0-3 parts of... Thioester antioxidant, 0-5 parts silicon carbide particles, 1.0-1.2 parts azodicarbonamide, 0.3 parts dibutyltin dilaurate, bottom layer reinforcement for chip removal and structural support, the bottom layer preparation materials by weight include 60-68 parts polyether polyurethane resin, 5-10 parts hexagonal boron nitride, 6-8 parts high molecular weight hindered amine 622, 0-3 parts thioester antioxidant, 4-5 parts chopped aramid fiber, 0-6 parts chopped glass fiber, 0.9-1.0 parts azodicarbonamide, 0.2 parts dibutyltin dilaurate.

[0011] Preferably, the surface layer has a closed-cell foam structure with a closed-cell rate of 65%-75% and an average pore size of 8μm-15μm; the bottom layer has an open-cell foam structure with an open-cell rate of 70%-80% and an average pore size of 25μm-35μm; the total thickness of the white pad is 3.0mm, of which the surface layer thickness is 1.0mm-1.3mm and the bottom layer thickness is 1.7mm-2.0mm.

[0012] Preferably, the micron-sized zirconium oxide and micron-sized silicon nitride in the surface layer are modified with silane or fluorosilane coupling agents, and the chopped aramid fibers and chopped glass fibers in the bottom layer are modified with acrylate or silane coupling agents.

[0013] Preferably, the edge of the white pad is provided with a wear-resistant and corrosion-resistant coating with a thickness of 50μm-60μm, and the coating contains alumina particles or aluminum nitride particles.

[0014] A method for preparing a white pad for rough polishing of wafer surfaces includes the following steps: S1: Modifying wear-resistant fillers such as micron-sized zirconium oxide and silicon nitride with a silane / fluorosilane coupling agent, ultrasonically dispersing and then vacuum drying; soaking aramid fibers and glass fibers in an acrylate / silane coupling agent, drying and cutting; ultrasonically dispersing graphene into a stable liquid; S2: Mixing polyether polyurethane with modified wear-resistant fillers, thermally conductive fillers, and antioxidants, melt-blending via a twin-screw extruder, and cooling and shaping via a three-roll calender to obtain a closed-cell surface sheet; S3: Adding thermally conductive fillers, antioxidants, and coupling-treated fibers to the polyether polyurethane, adjusting the extruder die temperature and speed, and extruding and calendering. S4: The surface and bottom sheets are preheated at 60-70℃ for 15-20 minutes, stacked, and then fused together by a three-roll calender. After water cooling to below 40℃, they are rolled up to obtain a composite sheet with a total thickness of 3.0±0.1mm. S5: A polyurethane coating slurry containing wear-resistant / corrosion-resistant particles is prepared and applied gravurely to a 20mm edge area of ​​the composite sheet. It is then dried at 80-90℃ for 10-15 minutes to cure. S6: The composite sheet is treated with atmospheric pressure plasma equipment for 4-5 minutes to achieve a surface contact angle of 65°-120°. S7: A fully automatic circular cutter is used to cut the sheet at a pressure of 0.5-0.6MPa and a speed of 1.8-2m / min to obtain a circular white pad with a diameter of 280mm.

[0015] Preferably, when the short-cut aramid fibers and short-cut glass fibers in S1 are soaked in a coupling agent, the coupling agent solution is an ethanol solution of 10% acrylate coupling agent or 5% silane coupling agent, the soaking time is 1 hour to 1.5 hours, the drying temperature is 100℃ to 110℃, and the fiber length after drying is controlled at 0.3mm to 0.5mm.

[0016] Preferably, the extruder temperature for preparing the surface sheet is 175-205℃ and the screw speed is 120-130 rpm, and the extruder temperature for preparing the bottom sheet is 180-185℃ and the screw speed is 90-110 rpm.

[0017] Preferably, the preheating temperature of the surface and bottom sheets is 60-70℃, the preheating time is 15-20 minutes, the roll temperature of the three-roll calender is 150-170℃, the linear pressure is 4-5MPa, and the composite sheet is water-cooled to below 40℃ before being wound up.

[0018] Preferably, the slurry for the edge-reinforcing coating in S5 includes polyurethane resin or fluorinated polyurethane resin, wear-resistant and corrosion-resistant particles, and solvent. The coating thickness is 50μm-60μm, and after coating, it is cured by drying at 80-90℃ for 10-15 minutes.

[0019] Preferably, in step S6, the plasma surface treatment uses argon or a fluorine / argon mixture as the working gas, with a treatment power of 120-150W and a treatment time of 4-5 minutes, so that the contact angle of the white pad surface reaches 65°-120°.

[0020] The technical effects and advantages of this invention are as follows:

[0021] In this invention, a dual-layer functional zoning design and targeted material system optimization achieve a synergistic improvement in wear resistance, aging resistance, thermal conductivity, and polishing precision. The surface layer focuses on polishing fluid storage and flexible grinding, while the bottom layer strengthens chip removal and structural support. Combined with the compounding of specific functional fillers, the white pad can meet the stable requirements of conventional coarse polishing and also cope with the performance challenges under special working conditions such as high load and strong corrosion. This solves the problem that traditional single-structure or simple composite designs cannot meet the needs of multiple scenarios.

[0022] In this invention, by replacing some nanomaterials with micron-level fillers, the dispersion process is simplified while ensuring core performance, reducing reliance on specialized equipment and lowering raw material costs. Furthermore, by optimizing foaming parameters and the composite process, compatibility with existing production lines is achieved, allowing for production conversion without large-scale equipment modifications. This significantly improves the feasibility and economy of industrial production, solving the problem of high costs associated with the complex materials or processes of traditional high-performance polishing pads.

[0023] In this invention, high molecular weight antioxidants and corrosion-resistant fillers are selected. Through interface modification and system compounding, the performance degradation caused by thermo-oxidative aging and chemical corrosion is effectively inhibited, extending the service life of the white pad. Whether used in long-term high-temperature environments or in polishing solutions with alternating acids and alkalis, it maintains stable hardness, strength, and structural integrity, overcoming the shortcomings of traditional white pads that have short lifespans due to the easy migration of anti-aging components and insufficient corrosion resistance.

[0024] In this invention, by precisely controlling the pore structure of the surface and bottom layers, uniform storage and efficient chip removal of the polishing slurry are achieved, reducing temperature fluctuations and debris residue during the polishing process. This lowers the risk of damage to the wafer surface and improves the consistency of polishing precision. Simultaneously, edge strengthening treatment further reduces edge breakage and over-polishing, ensuring the overall quality stability of large-size wafer polishing. Attached Figure Description

[0025] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0026] Figure 1 This is a flowchart illustrating the preparation process of the white pad for rough polishing of wafer surfaces according to the present invention. Detailed Implementation

[0027] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0028] Example 1

[0029] A white pad for rough polishing of wafer surfaces employs a double-layer composite design with a total thickness of 3.0 mm. The top layer, 1.2 mm thick, is a closed-cell foam structure with a 65% closed-cell rate and a pore size of 15 μm, emphasizing polishing fluid storage and low-temperature adaptability. The bottom layer, 1.8 mm thick, is an open-cell foam structure with a 75% open-cell rate and a pore size of 30 μm, emphasizing chip removal, heat dissipation, and high-pressure support. The top layer is prepared by weight of 60 parts polyether polyurethane resin, 15 parts micron-sized zirconium oxide, 4 parts hexagonal boron nitride, 10 parts high molecular weight hindered amine 622, 5 parts silicon carbide particles, 1.2 parts azodicarbonamide, and 0.3 parts dibutyltin dilaurate. The bottom layer is prepared by weight of 68 parts polyether polyurethane resin, 6 parts hexagonal boron nitride, 8 parts high molecular weight hindered amine 622, 5 parts chopped aramid fiber, 1.0 part azodicarbonamide, and 0.2 parts dibutyltin dilaurate.

[0030] The polyether-type polyurethane resin used was BASF's 3455 product. The micron-sized zirconium oxide was purchased from Shandong Dongjia Group Co., Ltd. (5-10μm specification). The hexagonal boron nitride was a 2μm reagent-grade material with 99% purity provided by Shanghai Aladdin Biochemical Technology Co., Ltd. The high molecular weight hindered amine 622 was a commercially available product from Ciba Specialty Chemicals, Switzerland. The silicon carbide particles were 20μm particle size products from Henan Sicheng Superhard Materials Co., Ltd. The chopped aramid fibers were 0.5mm length products from DuPont. The azodicarbonamide foaming agent was purchased from Jiangsu Suopu Group Co., Ltd. The dibutyltin dilaurate was an analytical grade reagent from Guangzhou Chemical Reagent Factory. The silane coupling agent KH-560, acrylate coupling agent, and other additives were all from Nanjing Shuguang Chemical Group Co., Ltd.

[0031] A white pad for rough polishing of wafer surfaces and its manufacturing method, comprising the following steps:

[0032] Step S1: Raw material pretreatment. First, surface modification of micron-sized zirconia is performed: 15 portions of micron-sized zirconia particles (5-10 μm in diameter) are placed in a reaction vessel, and an ethanol solution containing 3% silane coupling agent KH-560 is added. The particles are dispersed in an ultrasonic processor at 400W power and 40kHz frequency for 30 minutes. Then, they are transferred to a vacuum drying oven and dried at 80℃ for 2 hours until the moisture content is ≤0.5%. After drying, the particles are passed through a 100-mesh sieve to remove agglomerated particles for later use. Next, chopped aramid fibers are treated: 5 portions of chopped aramid fibers (0.5 mm in length) are weighed and immersed in an ethanol solution containing 10% acrylate coupling agent at room temperature for 1 hour. After immersion, they are dried in a 100℃ forced-air drying oven for 1 hour. After drying, they are cut into lengths of 0.3-0.5 mm for later use.

[0033] Step S2: Preparation of the surface sheet. The surface sheet was prepared using a twin-screw extruder with a length-to-diameter ratio of 32:1 and a four-zone temperature control system: 60 parts of polyether polyurethane resin were fed into the main feed port, and modified micron-sized zirconium oxide, 4 parts of hexagonal boron nitride with a particle size of 2 μm, 10 parts of high molecular weight hindered amine 622 and 5 parts of silicon carbide particles with a particle size of 20 μm were simultaneously added into the side feed port. At the same time, 1.2 parts of azodicarbonamide foaming agent and 0.3 parts of dibutyltin dilaurate catalyst were injected through a liquid metering pump. The extruder was set to have zone 1 temperatures of 175℃, zone 2 temperatures of 185℃, zone 3 temperatures of 195℃, and zone 4 temperatures of 200℃, a die temperature of 190℃, and a screw speed of 120 rpm. After the material was melted and blended, it was extruded from the die and cooled and shaped by a three-roll calender at a roller temperature of 30℃. A closed-cell surface sheet with a thickness of 1.2 mm, a density of 0.65 g / cm³, and a closed-cell rate of 65% was obtained at a traction speed of 5 m / min.

[0034] Step S3: Preparation of the bottom layer sheet. During the preparation of the bottom layer sheet, adjust the extruder die temperature to 185℃ and the screw speed to 100 rpm. Add 68 parts of polyether-type polyurethane resin to the main feed port, and add 6 parts of hexagonal boron nitride, 8 parts of high molecular weight hindered amine 622, and 5 parts of coupling-treated aramid fiber to the side feed port. Inject 1.0 part of azodicarbonamide and 0.2 parts of dibutyltin dilaurate using a liquid metering pump. The remaining processes are the same as for the surface layer sheet preparation. A 1.8 mm thick open-cell bottom layer sheet with a density of 0.75 g / cm³ and an open-cell rate of 75% is obtained at a traction speed of 4.5 m / min.

[0035] Step S4: Three-roll calendering composite forming. The prepared surface and bottom layer sheets are placed in a hot air circulating oven and preheated at 60°C for 15 minutes to enhance surface activity. Then, the closed-cell surface layer is stacked on top and the open-cell bottom layer is stacked on the bottom. The sheets are fed into a three-roll calender with the upper roll temperature at 160°C, the middle roll at 150°C, and the lower roll at 40°C. The roll linear pressure is controlled at 4MPa, and the sheets are passed through the roll gap at a composite speed of 5m / min to fuse the two layers together. After cooling to below 40°C by a water-cooled roll, the sheets are wound up to obtain a composite sheet with a total thickness of 3.0±0.1mm.

[0036] Step S5: Edge Reinforcement Coating. First, prepare the coating slurry: Add 80 parts of 50% solids polyurethane resin, 40 parts of 20μm alumina particles, and 20 parts of ethanol to a high-speed mixer. Stir at 1000 rpm for 30 minutes, then increase to 3000 rpm and continue stirring for 10 minutes. Filter impurities through a 400-mesh screen, controlling the slurry viscosity to 2000-3000 mPa·s. Apply the coating using a gravure printing press with an anilox roller at a depth of 50μm and a line count of 100 lines / inch. Fix the composite sheet on a conveyor belt and apply the slurry evenly to the 20mm edge area at a speed of 3m / min. After coating, dry in an 80℃ oven for 10 minutes to form an alumina-reinforced coating with a thickness of 50±5μm.

[0037] Step S6: Plasma surface treatment. The coated composite sheet is fed into an atmospheric pressure plasma treatment device. Argon gas with a purity ≥99.99% is used as the working gas with a flow rate of 500 sccm. The treatment power is set to 120W, and the distance between the spray gun and the material surface is controlled at 10mm. The sheet passes through the treatment area at a speed of 2m / min for 4 minutes, reducing the surface contact angle to 68°±3° and improving the surface hydrophilicity.

[0038] Step S7: Cutting. The composite sheet is processed using a fully automatic circular cutter. The cutting pressure is set to 0.5MPa, and the sheet is cut into circular white pads with a diameter of 280mm at a speed of 2m / min. The edge perpendicularity is controlled to be ≤0.1mm to complete the preparation.

[0039] Example 2

[0040] This embodiment provides a double-layer composite coarse polishing pad with a total thickness of 3.0 mm, emphasizing thermal conductivity. By optimizing the thermally conductive filler ratio and pore structure, it improves heat dissipation efficiency to adapt to high-load polishing scenarios. The surface layer is 1.0 mm thick, with a closed-cell foam structure, a closed-cell rate of 70%, and an average pore diameter of 10 μm, focusing on polishing fluid storage and low-resistance heat conduction; the bottom layer is 2.0 mm thick, with an open-cell foam structure, an open-cell rate of 80%, and an average pore diameter of 35 μm, focusing on rapid chip removal and efficient heat dissipation. The surface layer is prepared by weight of 58 parts polyether polyurethane resin, 12 parts micron-sized zirconium oxide, 8 parts hexagonal boron nitride, 2 parts graphene oxide, 10 parts high molecular weight hindered amine 622, 1.0 part azodicarbonamide, and 0.3 parts dibutyltin dilaurate; the bottom layer is prepared by weight of 65 parts polyether polyurethane resin, 10 parts hexagonal boron nitride, 8 parts high molecular weight hindered amine 622, 1.2 parts azodicarbonamide, 0.2 parts dibutyltin dilaurate, and 4 parts chopped aramid fiber.

[0041] It is important to note that the core requirement of this embodiment is to improve heat dissipation efficiency to cope with the frictional heat generated by high-load polishing. Hexagonal boron nitride is a layered material with high thermal conductivity and chemical stability. In this embodiment, the surface layer is increased to 8 parts and the bottom layer to 10 parts to construct a macroscopic thermally conductive network. Two parts of graphene oxide are added to fill the gaps between hexagonal boron nitride using their nanoscale effect, forming a synergistic thermal conductive path and increasing the overall thermal conductivity to 1.5 W / (m·K). Micron-sized zirconium oxide is the core wear-resistant component, but heat accumulation under high load is the main problem. Excessive pursuit of wear resistance will increase the rigidity of the material, which is not conducive to heat conduction. In this embodiment, while ensuring basic wear resistance, the material density is reduced to reduce thermal resistance, while making room for more thermally conductive fillers. In this embodiment, the surface layer thickness is reduced to decrease the heat conduction path length; the closed-cell ratio is increased to 70% and the pore size is reduced to 10μm, reducing the thermal resistance caused by polishing slurry retention and accelerating heat transfer to the underlying layer; the underlying layer is thickened, with an open-cell ratio increased to 80% and a pore size expanded to 35μm, enhancing air convection heat dissipation and silicon chip removal efficiency through larger pore spaces, avoiding localized overheating caused by debris accumulation. In this embodiment, the amount of polyurethane resin is reduced to make way for thermally conductive fillers, ensuring a moderate overall density of the composite material; the chopped aramid fiber is reduced to 4 parts, as the structural support is enhanced after the underlying layer is thickened, and this is moderately reduced to lower material costs, while also avoiding excessive fiber accumulation that hinders heat transfer.

[0042] This embodiment provides a method for manufacturing a double-layer composite coarse-polished white pad that emphasizes thermal conductivity, including the following steps:

[0043] Step S1: Raw material pretreatment. Take 12 parts of micron-sized zirconium oxide, add an ethanol solution containing 3% silane coupling agent KH-560, disperse in an ultrasonic processor at 400W power and 40kHz frequency for 30 minutes, then transfer to a vacuum drying oven and dry at 80℃ for 2 hours until the moisture content is ≤0.5%. After drying, pass through a 100-mesh sieve for later use. Take 2 parts of graphene oxide, add an N-methylpyrrolidone solution, and ultrasonically treat at 500W for 1 hour to form a uniform dispersion for later use. Take 4 parts of chopped aramid fibers, immerse in a 10% acrylate coupling agent solution for 1 hour, dry at 100℃ for 1 hour, and cut into 0.3-0.5mm pieces for later use.

[0044] Step S2: Preparation of the surface sheet. A twin-screw extruder with a length-to-diameter ratio of 32:1 and a four-zone temperature control system was used. 58 parts of polyether-type polyurethane resin were fed into the main feed port, while modified micronized zirconium oxide, 8 parts of hexagonal boron nitride, 10 parts of antioxidant 622, and graphene oxide dispersion were simultaneously added into the side feed port. 1.0 part of azodicarbonamide and 0.3 parts of catalyst were injected by a liquid metering pump. The extruder was set to 175℃ in zone 1, 185℃ in zone 2, 200℃ in zone 3, and 205℃ in zone 4, with a die temperature of 195℃ and a screw speed of 130 rpm. After melt blending, the material was extruded and cooled and shaped by a three-roll calender at a roller temperature of 35℃. A closed-cell surface sheet with a thickness of 1.0 mm and a density of 0.68 g / cm³ was obtained at a traction speed of 5 m / min.

[0045] Step S3: Preparation of the bottom layer sheet. Adjust the extruder die temperature to 185℃ and the screw speed to 110rpm. Add 65 parts of polyether-type polyurethane resin to the main feed port, and add 10 parts of hexagonal boron nitride, 8 parts of antioxidant 622, and 4 parts of coupling-treated aramid fiber to the side feed port. Inject 1.2 parts of azodicarbonamide and 0.2 parts of catalyst using a liquid metering pump. The remaining processes are the same as for the surface layer. Obtain an open-cell bottom layer sheet with a thickness of 2.0mm and a density of 0.72g / cm³ at a traction speed of 4.5m / min.

[0046] Step S4: Three-roll calendering composite forming. Preheat the surface and bottom layers in a 65℃ oven for 15 minutes, stack them with the surface layer on top and the bottom layer on the bottom, and feed them into a three-roll calender with the upper roll at 165℃, the middle roll at 170℃, and the lower roll at 40℃. Control the roller linear pressure at 4.5MPa and the composite speed at 5m / min. After cooling to below 40℃ by water-cooled rollers, the composite sheet is wound up to obtain a total thickness of 3.0±0.1mm.

[0047] Step S5: Edge Reinforcement Coating. Prepare the coating slurry: 80 parts polyurethane resin (50% solids content) + 40 parts alumina particles (20μm) + 20 parts ethanol. Stir at 3000 rpm for 10 minutes, filter, and control the viscosity to 2500±500 mPa·s. Apply the slurry to a 20mm edge area using an anilox roller on a gravure printing press, with a depth of 50μm. Dry in an 80℃ oven at 3m / min for 10 minutes to form a 50±5μm coating.

[0048] Step S6: Plasma surface treatment. The composite sheet is fed into an atmospheric pressure plasma device with an argon flow rate of 500 sccm, a power of 120W, a spray gun distance of 10mm, and a treatment speed of 2m / min for 4 minutes. The surface contact angle is controlled at 65°±3°.

[0049] Step S7: Cutting process. Use a fully automatic circular cutter, set the pressure to 0.5MPa and the speed to 2m / min, to cut into circular white pads with a diameter of 280mm and an edge perpendicularity of ≤0.1mm.

[0050] Example 3

[0051] This embodiment provides a double-layer composite coarse polishing pad with a total thickness of 3.0 mm, emphasizing chemical corrosion resistance. Through optimized corrosion-resistant fillers and interface modification, it is suitable for polishing slurries containing highly corrosive components. The surface layer is 1.3 mm thick, with a closed-cell foam structure, a closed-cell rate of 75%, and an average pore size of 8 μm, focusing on preventing corrosive media penetration and ensuring uniform distribution of the polishing slurry. The bottom layer is 1.7 mm thick, with an open-cell foam structure, an open-cell rate of 70%, and an average pore size of 25 μm, focusing on structural support and low-residue chip removal. The surface layer is prepared by weight of 55 parts polyether polyurethane resin, 18 parts micron-sized silicon nitride, 5 parts hexagonal boron nitride, 5 parts fluorosilane-modified silica (newly added), 8 parts high molecular weight hindered amine 622, 3 parts thioester antioxidant (newly added), 1.1 parts azodicarbonamide, and 0.3 parts dibutyltin dilaurate; the bottom layer is prepared by weight of 60 parts polyether polyurethane resin, 5 parts hexagonal boron nitride, 7 parts high molecular weight hindered amine 622, 3 parts thioester antioxidant (newly added), 0.9 parts azodicarbonamide, 0.2 parts dibutyltin dilaurate, and 6 parts chopped glass fiber.

[0052] It is important to note that this embodiment is designed for highly corrosive environments, with a core optimization focus on enhancing chemical resistance. Micron-sized silicon nitride combined with fluorosilane-modified silica forms a dual protection of physical barrier and chemical inertness, improving the surface's resistance to permeation. A newly added thioester antioxidant synergistically enhances free radical capture efficiency in highly oxidizing environments, preventing polyurethane molecular chain breakage. The surface closed-porosity is increased to 75% with a pore size of 8μm, reducing polishing fluid retention and penetration; the bottom open-porosity is reduced to 70% with a pore size of 25μm, lowering the risk of corrosive media residue.

[0053] This embodiment provides a method for manufacturing a double-layer composite coarse polished white pad with an emphasis on chemical corrosion resistance, including the following steps:

[0054] Step S1: Raw material pretreatment. Take 18 parts of micron-sized silicon nitride, add an ethanol solution containing 5% fluorosilane coupling agent, disperse in an ultrasonic processor at 500W power and 40kHz frequency for 40 minutes, vacuum dry at 90℃ for 2.5 hours until the moisture content is ≤0.3%, and pass through a 120-mesh sieve for later use. Take 5 parts of silicon dioxide, immerse in a 2% fluorosilane solution and stir for 30 minutes, dry at 80℃ for 1.5 hours to form a hydrophobic surface with a contact angle >110°, improving liquid penetration resistance. Take 6 parts of chopped glass fiber, immerse in a 5% silane coupling agent KH-570 solution for 1.5 hours, dry at 110℃ for 1 hour, and cut into 0.3-0.5mm pieces for later use.

[0055] Step S2: Preparation of the surface sheet. A twin-screw extruder with a length-to-diameter ratio of 32:1 and a four-zone temperature control system was used. 55 parts of polyether-type polyurethane resin were fed into the main feed port, while modified micronized silicon nitride, 5 parts of hexagonal boron nitride, 8 parts of antioxidant 622, 3 parts of DLTP, and fluorosilane-modified silica were simultaneously added into the side feed port. A liquid metering pump injected 1.1 parts of azodicarbonamide and 0.3 parts of catalyst. The extruder was set to 180℃ in zone 1, 190℃ in zone 2, 200℃ in zone 3, and 205℃ in zone 4, with a die temperature of 195℃ and a screw speed of 110 rpm. After melt blending, the material was extruded and cooled and shaped using a three-roll calender at a roller temperature of 30℃. A closed-cell surface sheet with a thickness of 1.3 mm and a density of 0.70 g / cm³ was obtained at a traction speed of 4.5 m / min.

[0056] Step S3: Preparation of the bottom layer sheet. Adjust the extruder die temperature to 180℃ and the screw speed to 90rpm. Add 60 parts of polyether polyurethane resin to the main feed port, and add 5 parts of hexagonal boron nitride, 7 parts of antioxidant 622, 3 parts of DLTP and 6 parts of coupling-treated glass fiber to the side feed port. Inject 0.9 parts of azodicarbonamide and 0.2 parts of catalyst into the liquid metering pump. The remaining processes are the same as the surface layer. Obtain an open-cell bottom layer sheet with a thickness of 1.7mm and a density of 0.73g / cm³ at a traction speed of 4m / min.

[0057] Step S4: Three-roll calendering composite forming. Preheat the surface and bottom layers in a 70℃ oven for 20 minutes, stack them with the surface layer on top and the bottom layer on the bottom, and feed them into a three-roll calender with the upper roll at 170℃, the middle roll at 160℃, and the lower roll at 40℃. Control the roller linear pressure at 5MPa and the composite speed at 4.5m / min. After cooling to below 35℃ by water-cooled rollers, the composite sheet is wound up to obtain a total thickness of 3.0±0.1mm.

[0058] Step S5: Edge Reinforcement Coating. Prepare the corrosion-resistant coating slurry: 70 parts fluorine-modified polyurethane resin (50% solids content) + 30 parts aluminum nitride particles (10μm) + 25 parts ethanol. Stir at 3000 rpm for 15 minutes, filter, and control the viscosity to 3000±500 mPa·s. Apply the slurry to a 20mm edge area using a gravure printing press anilox roller to a depth of 60μm. Dry in a 90℃ oven at 2.5m / min for 15 minutes, forming a 60±5μm coating with a weight loss of <3% after 72 hours of acid and alkali immersion.

[0059] Step S6: Plasma surface treatment. The composite sheet is fed into an atmospheric pressure plasma device with a working gas flow rate of 500 sccm, a power of 150W, and a spray gun distance of 8mm, using a fluorine / argon mixed gas volume ratio of 1:9 and a spray gun distance of 8mm. The treatment is carried out at a speed of 1.5m / min for 5 minutes to form a fluorocarbon layer with a contact angle >120°, which enhances the resistance to liquid wetting.

[0060] Step S7: Cutting process. Use a fully automatic circular cutter with a pressure of 0.6MPa and a speed of 1.8m / min to cut into circular white pads with a diameter of 280mm and an edge perpendicularity of ≤0.1mm.

[0061] Comparative Example 1

[0062] The same double-layer structure as in Example 1 is used, but without any wear-resistant, thermally conductive, or anti-aging functional fillers. The surface layer consists of 98.5 parts by weight of polyether polyurethane resin, 1.2 parts by weight of azodicarbonamide, and 0.3 parts by weight of dibutyltin dilaurate; the bottom layer consists of 98.8 parts by weight of polyether polyurethane resin, 1.0 part by weight of azodicarbonamide, and 0.2 parts by weight of dibutyltin dilaurate. Except for the absence of functional fillers such as micron-sized zirconium oxide, hexagonal boron nitride, and antioxidant 622, the preparation steps are completely identical to those in Example 1.

[0063] Comparative Example 2

[0064] The material adopts a single-layer homogeneous structure, and its composition is completely consistent with the surface layer of Example 1, but without the underlying support structure. In terms of preparation method, the surface material of Example 1 is extruded into sheets separately, and the edges are directly coated and surface treated, without the underlying composite step.

[0065] Performance testing

[0066] To verify the technical effect of the present invention, the white pads prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to the following performance tests, and the test results are shown in Table 1:

[0067] Abrasion resistance test: According to ASTM D4060 standard, the Taber abrasion tester was used with a CS-10 grinding wheel. A load of 1000g was applied and the wear was measured after 1000 revolutions.

[0068] Thermal conductivity was tested according to ISO 22007-2 using a HotDisk TPS2500S thermal constant analyzer at 25°C.

[0069] Aging resistance test: Place the sample in an environment of 85℃ / 85%RH for 500 hours, then measure the hardness decay rate according to GB / T531.1 and the tensile strength retention rate according to GB / T1040.3.

[0070] Chemical corrosion resistance test: Immerse in alkaline polishing solution at pH=12 at 60°C for 72 hours, calculate the mass loss rate and detect the hardness change.

[0071] Polishing performance was tested: 300mm silicon wafers were polished on a SMIC CP-4 CMP machine with process parameters of 4psi pressure, 120 / 114rpm rotation speed, and 300ml / min polishing fluid flow rate. The removal rate was measured by the four-point probe method, the surface roughness Ra was detected by a white light interferometer, and the edge collapse was measured by a laser displacement sensor.

[0072] Test service life: Polish continuously until the removal rate decreases by more than 20%, or the number of surface defects is more than 50 per piece, and record the number of polished pieces.

[0073] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Wear amount (mg) 42 28 38 125 58 Thermal conductivity (W / m·K) 0.95 1.52 0.92 0.25 0.88 Aging hardness reduction (%) 8.5 9.2 5.3 43.6 32.7 Tensile strength retention rate (%) 92 98 95 51 70 Mass loss due to alkaline corrosion (%) 1.8 2.1 0.5 12.5 8.7 Polishing removal rate (nm / min) 820 950 780 320 610 Surface roughness Ra (nm) 3.2 3.8 2.5 8.5 5.2 Edge collapse amount (μm) 0.15 0.18 0.12 1.05 0.65 Service life (sheet / pad) 800 1200 1000 120 350

[0074] Table 1

[0075] The wear rate of Examples 1-3 was significantly lower than that of the comparative examples, with Example 2 showing the best performance due to its high filler content. The hexagonal boron nitride and graphene oxide synergistic thermal conductive network of Example 2 resulted in a thermal conductivity of 1.52 W / m·K, which is 508% higher than that of Comparative Example 1. Due to the antioxidant 622 and thioester system, the hardness of Example 3 decreased by only 5.3% after aging, and the tensile strength retention rate was 95%. The fluorosilane modification and aluminum nitride coating of Example 3 achieved ultra-low mass loss, which is far superior to that of the comparative examples. The roughness and edge collapse of all examples met the requirements of advanced processes, with Example 3 showing outstanding performance in low-damage polishing. Example 2 achieved a design life of 1200 pieces due to enhanced thermal conductivity, which is 900% higher than that of Comparative Example 1.

[0076] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A white pad for rough polishing of a wafer surface, characterized by, The white pad comprises a surface layer and a bottom layer, the surface layer is mainly used for polishing liquid storage and flexible polishing, the preparation material of the surface layer comprises, by weight ratio, 55-60 parts of polyether type polyurethane resin, 12-18 parts of micron zirconium oxide, 15-18 parts of micron silicon nitride, 4-8 parts of hexagonal boron nitride, 1-2 parts of graphene oxide, 4-6 parts of fluorosilane modified silicon dioxide, 7-10 parts of high molecular weight hindered amine 622, 0-3 parts of thioester antioxidant, 0-5 parts of silicon carbide particles, 1.0-1.2 parts of azodicarbonamide, and 0.3 parts of dibutyltin dilaurate, the bottom layer is mainly used for chip removal and structural support, the preparation material of the bottom layer comprises, by weight ratio, 60-68 parts of polyether type polyurethane resin, 5-10 parts of hexagonal boron nitride, 6-8 parts of high molecular weight hindered amine 622, 0-3 parts of thioester antioxidant, 4-5 parts of short aramid fiber, 0-6 parts of short glass fiber, 0.9-1.0 parts of azodicarbonamide, and 0.2 parts of dibutyltin dilaurate.

2. A white pad for rough polishing of wafer surface according to claim 1, wherein: The surface layer is a closed-cell foam structure, the closed-cell rate is 65%-75%, and the average pore size is 8-15 μm; the bottom layer is an open-cell foam structure, the open-cell rate is 70%-80%, and the average pore size is 25-35 μm; the total thickness of the white pad is 3.0 mm, wherein the thickness of the surface layer is 1.0-1.3 mm, and the thickness of the bottom layer is 1.7-2.0 mm.

3. A white pad for rough polishing of wafer surface according to claim 1, wherein: The micron zirconium oxide and the micron silicon nitride in the surface layer are modified by silane or fluorosilane coupling agent, and the short aramid fiber and the short glass fiber in the bottom layer are modified by acrylate or silane coupling agent.

4. A white pad for rough polishing of wafer surface according to claim 1, wherein: The edge of the white pad is provided with a wear-resistant and corrosion-resistant coating, the thickness of the coating is 50-60 μm, and the coating contains aluminum oxide particles or aluminum nitride particles.

5. A method for making a polishing pad for rough polishing of a wafer surface, for producing a polishing pad for rough polishing of a wafer surface according to any one of claims 1 to 4, characterized in that The method comprises the following steps: S1: modifying the micron zirconium oxide and the micron silicon nitride wear-resistant filler with silane / fluorosilane coupling agent, ultrasonic dispersion, vacuum drying, soaking aramid fiber and glass fiber in acrylate / silane coupling agent, drying and cutting, and ultrasonic dispersion of graphene oxide to obtain a stable liquid; S2: mixing polyether type polyurethane with modified wear-resistant filler, heat-conducting filler and antioxidant, melt blending by a double screw extruder, cooling and shaping by a three-roll calender to obtain a closed-cell surface layer sheet; S3: adding polyether type polyurethane, heat-conducting filler, antioxidant and coupling treated fiber, adjusting the temperature and rotating speed of the extruder die, and extruding, calendering and shaping to obtain an open-cell bottom layer sheet; S4: preheating the surface layer sheet and the bottom layer sheet at 60-70 °C for 15-20 minutes, stacking and melt blending by a three-roll calender, water cooling to below 40 °C and winding to obtain a composite sheet with a total thickness of 3.0±0.1 mm; S5: preparing a polyurethane coating slurry containing wear-resistant / corrosion-resistant particles, gravure coating the slurry on the edge of the composite sheet in a 20 mm area, drying at 80-90 °C for 10-15 minutes to solidify; S6: treating the composite sheet by a normal pressure plasma device for 4-5 minutes to make the surface contact angle reach 65-120°; S7: cutting the composite sheet by a full-automatic circular knife cutting machine at a pressure of 0.5-0.6 MPa and a speed of 1.8-2 m / min to obtain a circular white pad with a diameter of 280 mm.

6. The method of claim 5, wherein the method further comprises: The S1 short aramid fiber and short glass fiber are soaked by coupling agent, the coupling agent solution is 10% acrylate coupling agent or 5% silane coupling agent ethanol solution, the soaking time is 1-1.5 hours, the drying temperature is 100-110℃, and the fiber length after drying is controlled at 0.3-0.5mm.

7. The method of claim 5, wherein the method further comprises the steps of: providing a plurality of abrasive particles; and mixing the plurality of abrasive particles with the polymer to form the polishing pad. The temperature of the extruder for preparing the surface layer sheet is 175-205℃, and the screw rotation speed is 120-130rpm, the temperature of the extruder for preparing the bottom layer sheet is 180-185℃, and the screw rotation speed is 90-110rpm.

8. The method for manufacturing a white pad for rough polishing of a wafer surface according to claim 5, characterized in that: The preheating temperature of the surface layer and bottom layer sheet is 60-70℃, the preheating time is 15-20 minutes, the roller temperature of the three-roll calender is 150-170℃, the linear pressure is 4-5MPa, and the composite sheet is cooled by water to below 40℃ and then wound.

9. The method for manufacturing a white pad for rough polishing of a wafer surface according to claim 5, characterized in that: The slurry of the S5 edge strengthening coating includes polyurethane resin or fluorine modified polyurethane resin, wear-resistant and corrosion-resistant particles and solvent, the coating thickness is 50-60μm, and the coating is dried at 80-90℃ for 10-15 minutes for solidification.

10. A method for fabricating a white pad for rough polishing of a wafer surface according to claim 5, characterized in that: The plasma surface treatment in S6 uses argon or fluorine / argon mixed gas as working gas, the treatment power is 120-150W, and the treatment time is 4-5 minutes, so that the white pad surface contact angle reaches 65-120°.

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