A production process of cmp polishing pad with semi-continuous surface thickness

Abstract

The application relates to the polishing technical field and discloses a CMP polishing pad production process for semi-continuous preparation of surface thickness, which solves the problem of insufficient uniformity of the surface layer and the bubble hole in the prior art. A modified thermoplastic polyurethane elastomer is prepared, which contains polyether type thermoplastic polyurethane, ethylene-vinyl acetate copolymer, silanized nano SiO2 and the like, and the raw materials are pretreated, silanized and modified, and premixed and granulated to obtain particles; then the base material is regenerated, a functional layer is coated, step-by-step foaming and shaping are carried out, laser microprocessing is carried out, and sorting and detection are carried out to obtain the polishing pad; the functional layer is coated semi-continuously and foamed step-by-step, the stability of the polishing pad surface layer thickness and the uniformity of the bubble hole structure are improved by combining the shaping and nucleation of the modified elastomer, the pressure distribution and the polishing liquid transmission efficiency during wafer polishing are improved, local over-polishing, under-polishing and surface defects are reduced, the material wear resistance is enhanced, the service life is prolonged, and the polishing pad is especially suitable for planarization treatment of advanced processes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polishing, in particular to a CMP polishing pad production process for semi-continuous preparation of surface thickness. BACKGROUND

[0002] In the field of semiconductor manufacturing, the chemical mechanical polishing (CMP) process is a key technology for achieving nanoscale planarization of wafer surfaces. The CMP polishing pad, as a key consumable for this process, directly affects the polishing quality of wafers and the yield of chip manufacturing in terms of structural precision and performance stability. Traditional CMP polishing pad production processes mainly include batch production and continuous production. Batch production processes complete raw material mixing, foaming molding, and post-processing through a segmented process. Continuous processes improve productivity by leveraging the continuity of production lines. As semiconductor device processes evolve towards 3nm and below, higher requirements are placed on the uniformity of polishing pad surface thickness and the controllability of microstructure. Existing processes need to be further optimized to meet the demand for high-precision and large-scale production. In this context, developing a new production process has important technical value and industrial application significance.

[0003] The existing technology with publication number CN116766077A discloses a CMP polishing pad and a preparation method thereof, including the following steps: a portion of the solvent is first stirred, a portion of the additive is added, the stirring speed is increased after uniform stirring, a portion of the additive is then added, and uniform stirring is performed to obtain a mixture A; the remaining solvent and the remaining additive are stirred uniformly, a portion of the polyurethane resin is slowly added during stirring, uniform stirring is performed, a portion of the carbon powder is slowly added, the stirring speed is increased after uniform stirring, continuous stirring is performed, a portion of the polyurethane resin is then added, uniform stirring is performed, and a mixture B is obtained; the mixture A is added to the mixture B, uniform stirring is performed, the remaining polyurethane resin is added, uniform stirring is performed, a mixture C is obtained, filtration is performed, vacuum degassing is performed, and a polyurethane slurry is obtained; the polyurethane slurry is coated on a non-woven fabric to obtain the CMP polishing pad. The existing technology with publication number CN114536212B also discloses a microporous thermoplastic polyurethane polishing pad and a semi-continuous preparation method thereof, including the following steps: high-hardness thermoplastic polyurethane and an additive are melt-extruded, calendered, and wound; the wound material is subjected to high-pressure fluid immersion, low-temperature gas locking, low-temperature storage, temperature increase foaming, and winding to obtain a foamed wound material; the foamed wound material is peeled, punched, and a top pad is obtained; the top pad is ground flat, slotted, and attached with a backing adhesive or a buffer layer and a backing adhesive to obtain the microporous thermoplastic polyurethane polishing pad; the hardness of the high-hardness thermoplastic polyurethane is 55-85HD; the hardness of the top pad is 25-80HD, the thickness is 1.3-2.0 millimeters, the density is 0.1-1.0g / cm3, and the cell size is 1-200 microns; the high-pressure fluid is carbon dioxide and nitrogen gas. The polishing pad prepared by the method of the existing technology has excellent polishing effect and polishing rate.

[0004] For the above and existing related technology, the inventor believes that there are often the following defects:

[0005] 1. The thickness control precision of the surface layer prepared by the prior art is insufficient. In the existing process, the uneven penetration of the slurry and the difference in the cell caused by the temperature difference between the core layer and the surface layer in the foaming method result in a large thickness deviation of the surface layer. The uneven pressure distribution on the wafer surface during polishing causes local over-polishing or under-polishing, affecting the polishing uniformity.

[0006] 2. The cell structure uniformity of the prior art is poor. The pore size distribution formed by the solvent volatilization in the coating process is wide. The single gas impregnation in the foaming process easily leads to the mixing of large pores in the surface layer and small pores in the core layer, and the cell density deviation is too large. Not only does it reduce the polishing liquid transport efficiency and material removal rate, but also it shortens the service life of the polishing pad due to local rapid wear. SUMMARY

[0007] The technical problem to be solved by the present application is that the prior art has the defect of insufficient uniformity of the surface layer and the cell. Therefore, we propose a CMP polishing pad production process for semi-continuous preparation of surface thickness.

[0008] In order to achieve the above purpose, the following technical scheme is adopted in the present application: A CMP polishing pad production process for semi-continuous preparation of surface thickness, comprising a substrate layer and a functional layer thereon. The preparation material of the functional layer includes 65-75 parts of modified thermoplastic polyurethane elastomer, 8-12 parts of thermal expansion microspheres, 0.3-0.7 parts of silanized nano silicon dioxide, and 0.8-1.2 parts of silane coupling agent KH-550 by weight. The preparation material of the modified thermoplastic polyurethane elastomer includes 80-90 parts of polyether type thermoplastic polyurethane, 5-15 parts of ethylene-vinyl acetate copolymer and silanized nano SiO2 by weight. By adjusting the ratio of thermoplastic polyurethane and ethylene-vinyl acetate copolymer and the dispersibility of nano fillers, combined with the semi-continuous coating and step foaming process of the functional layer, the high-precision control of the surface layer thickness and the uniform distribution of the cell structure are realized. The step foaming process includes supercritical CO2 penetration, N2 sealing and low-temperature rapid cooling and gas locking, and gradient temperature foaming steps in sequence.

[0009] Preferably, the substrate layer is prepared from regenerated polyurethane particles, which include 100 parts of regenerated polyurethane particles by weight. The regenerated polyurethane particles are derived from polishing pad cutting scrap, which is recycled after crushing and granulation.

[0010] Preferably, in the modified thermoplastic polyurethane elastomer, the content of polyether type thermoplastic polyurethane is 90 parts, and the content of ethylene-vinyl acetate copolymer is 5 parts. The functional layer focuses on improving the thickness stability and wear resistance of the surface layer. The Shore hardness of the functional layer is 67-69 degrees, and the tensile strength is 41-43 MPa. It is suitable for edge planarization and polishing of large-size wafers. The thickness difference between the edge and the center is ≤0.01 mm.

[0011] Preferably, in the modified thermoplastic polyurethane elastomer, the weight ratio of thermoplastic polyurethane to ethylene-vinyl acetate copolymer is 16:3. The functional layer focuses on optimizing the cell size distribution and polishing liquid transmission uniformity. The Shore hardness of the functional layer is 61-63 degrees, and the elongation at break is 500-560%. It is suitable for high-precision node wafer polishing scenarios. The cell size distribution is concentrated in 15-35 microns.

[0012] Preferably, the thickness ratio of the substrate layer to the functional layer is 4:1, and the total thickness is 1.25 mm. The functional layer has a closed cell rate of ≥92% and an average cell density of ≥510 cells / mm2. The substrate layer and the functional layer cooperatively realize uniform pressure transmission and efficient polishing liquid storage and transmission.

[0013] A CMP polishing pad production process for semi-continuous preparation of surface thickness, for preparing the CMP polishing pad according to any one of claims 1-5, comprising the following steps: S1: substrate regeneration treatment, crushing, screening, washing and drying the polishing pad scraps, then melting and granulating, calendering into a coiled material and performing plasma cleaning and surface activation treatment of nano-alumina etching; S2: functional layer slurry coating, mixing modified thermoplastic polyurethane elastomer, thermally expandable microspheres, silanized nano-SiO2 and coupling agent, adding solvent to prepare slurry, coating on the surface of the substrate layer by slot coater, and controlling the dry film thickness after drying; S3: step foaming and shaping, sequentially performing supercritical CO2 penetration, N2 sealing and low-temperature rapid cooling and gas locking, and then forming a closed cell structure by gradient heating and foaming; S4: laser microprocessing, sanding the surface of the foamed functional layer to smooth, and then engraving spiral grooves using femtosecond laser; S5: sorting, detecting and slitting and packaging, detecting the thickness, cell structure and surface defects of the polishing pad, and then slitting and packaging into specified specifications after passing the detection.

[0014] Preferably, the modified thermoplastic polyurethane elastomer is prepared mainly by the following methods: C1: raw material pretreatment, sieving and drying polyether type thermoplastic polyurethane and ethylene-vinyl acetate copolymer respectively, and removing surface adsorbed water from nano-SiO2 by vacuum drying; C2: preparation of silanized nano-SiO2, dispersing nano-SiO2 in ethanol-water mixture, adding silane coupling agent after reaction, and obtaining silanized nano-SiO2 by centrifugation, washing and drying; C3: preparation of premix, mixing dried polyether type thermoplastic polyurethane, ethylene-vinyl acetate copolymer and silanized nano-SiO2 uniformly; C4: melt blending and granulation, melt blending the premix by a twin-screw extruder, and obtaining modified thermoplastic polyurethane elastomer particles by extrusion, cooling and granulation.

[0015] Preferably, during the functional layer slurry coating process, for the scenario of focusing on improving the thickness stability of the surface layer, the dry mixing time is extended by 1-2 minutes to ensure uniform contact of the high-rigidity modified thermoplastic polyurethane elastomer with other components; the solvent usage is increased by 1-3% to adapt to the high-viscosity matrix, and the slurry viscosity is maintained at 1400-1600 cP; the die pressure adjustment accuracy is improved to 0.005 MPa, the edge thickness deviation is reduced by precise control of the coating pressure, and the demand for large-size wafer edge planarization polishing is adapted.

[0016] Preferably, during the step-by-step foaming and shaping process, for the scenario of focusing on optimizing the cell size distribution, the supercritical CO2 penetration time is shortened to 12-18 minutes, and the high gas solubility characteristics of the high-flexibility modified thermoplastic polyurethane elastomer are used to ensure sufficient penetration; the heating rate is increased to 2-4 ℃ / min in the gradient heating stage, the cell merging is reduced by accelerating the heating rate, and the polishing liquid transport uniformity is improved by parameter regulation in the target cell size interval of 15-35 microns, adapting to the high-precision node wafer polishing demand.

[0017] Preferably, after the substrate regeneration treatment, the substrate roll directly enters the functional layer slurry coating process through the transmission roller group, the coated roll is directly sent to the step-by-step foaming and shaping process through the transition transmission structure, the foamed and shaped roll continues to be transmitted to the laser microprocessing process through the same transmission path, and the microprocessed roll is directly transferred to the sorting and detection link, and the processes are continuously transferred without interruption through coordinated matching.

[0018] The technical effects and advantages of the present application are as follows:

[0019] In the present application, through the formula design of the modified thermoplastic polyurethane elastomer, combined with real-time thickness detection and closed-loop control in the semi-continuous coating process, the surface layer thickness deviation caused by uneven material shrinkage and slurry penetration difference is effectively inhibited, ensuring more uniform wafer surface pressure distribution during polishing and avoiding local over-polishing or under-polishing phenomenon.

[0020] In the present application, by means of the synergistic effect of high-efficiency nucleation of silanized nano-SiO2 and step-by-step foaming process, the problems of wide bubble size distribution and large structural difference between surface layer and core layer in the prior art are solved, the bubble distribution is more concentrated, the polishing liquid transmission efficiency and material removal consistency are improved, and the local wear difference caused by uneven bubbles is reduced.

[0021] In the present application, by optimizing the surface layer thickness and bubble structure, the material removal is more uniform during polishing, the generation of defects such as scratches and pits on the wafer surface is reduced, and the polishing rate is more stable, which adapts to the polishing needs of high-precision semiconductor wafers, especially for advanced process planarization. BRIEF DESCRIPTION OF DRAWINGS

[0022] The disclosure of the present application will be described 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 the present application. In the drawings, the same reference numerals are used to refer to the same parts:

[0023] Figure 1 Preparation flow chart of the modified thermoplastic polyurethane elastomer of the present application;

[0024] Figure 2 Preparation flow chart of the CMP polishing pad of the present application. DETAILED DESCRIPTION

[0025] It is easy to understand that according to the technical scheme of the present application, those skilled in the art can propose a variety of structures and implementation ways which can be replaced with each other without changing the essential spirit of the present application. Therefore, the following specific embodiments and drawings are only exemplary description of the technical scheme of the present application, and should not be regarded as the whole or as the limitation or restriction of the technical scheme of the present application.

[0026] Preparation Example 1

[0027] Referring to Figure 1 As shown in the figure, a modified thermoplastic polyurethane elastomer can provide excellent surface layer setting ability and bubble nucleation uniformity for the functional layer of the CMP polishing pad, effectively solve the problems of large surface layer thickness deviation and wide bubble size distribution in the prior art, and be suitable for high-precision polishing scenes. The preparation materials include 85 parts of polyether type thermoplastic polyurethane, 10 parts of ethylene-vinyl acetate copolymer, 5 parts of nano-SiO2, 0.5 parts of silane coupling agent KH-570, 200 parts of anhydrous ethanol, and 20 parts of deionized water.

[0028] A preparation method of a modified thermoplastic polyurethane elastomer, comprising the following steps:

[0029] Step C1 : Raw material pretreatment. 85 parts of polyether thermoplastic polyurethane particles were sieved through an 80-mesh screen to remove mechanical impurities, placed in a forced air dryer, dried at 120°C for 2 hours, and the moisture content was detected by a Karl Fischer moisture meter to be ≤0.05% to prevent air bubbles from being generated during subsequent melt blending; 10 parts of ethylene-vinyl acetate copolymer particles were sieved through an 80-mesh screen and dried under the same conditions to ensure the same degree of dryness as the polyether thermoplastic polyurethane to avoid uneven dispersion due to moisture differences during mixing; the nano-SiO2 was placed in a vacuum drying oven and dried at 80°C for 4 hours to remove surface adsorbed water and improve the grafting efficiency of the silane coupling agent.

[0030] Step C2: Preparation of silanized nano-SiO2. In a 500-mL three-necked flask, 200 parts of anhydrous ethanol and 20 parts of deionized water were added, and magnetic stirring was maintained at 500 r / min for 10 minutes to form a uniform mixed solvent. 5 parts of pretreated nano-SiO2 was slowly added to the mixed solvent, and an ultrasonic disperser was turned on with a power of 500 W and a frequency of 25 kHz. Ultrasonic treatment was performed for 30 minutes, during which the machine was stopped every 10 minutes to observe whether there were visible agglomerated particles. A white suspension was finally obtained. The three-necked flask was placed in a constant temperature water bath, heated to 60°C, and magnetic stirring was maintained at 800 r / min for 2 hours. During this period, 0.5 parts of silane coupling agent KH-570 was added dropwise using a pipette, and the dropwise addition rate was controlled at 1 drop per second to avoid local concentration of the coupling agent leading to self-polymerization. After stirring, the heating was turned off, the suspension was transferred to a centrifuge tube, and centrifugation was performed at 8000 r / min for 10 minutes. The supernatant was removed, and the precipitate was washed with anhydrous ethanol three times, each time for 5 minutes. The unreacted coupling agent was removed, and finally the sample was placed in a vacuum drying oven at 80°C under -0.09 MPa for 4 hours. The silanized nano-SiO2 powder was obtained by sieving through a 100-mesh screen, and the surface hydroxyl conversion rate was 82%. FTIR detection of the Si-O-C characteristic peak at 1160 cm -1 The strength ratio is ≥1.

[0031] Step C3: Preparation of premix. The dried 85 parts of polyether thermoplastic polyurethane particles and 10 parts of ethylene-vinyl acetate copolymer particles were added to a GHJ-5 high-speed mixer, and the speed was set to 1200 r / min for 3 minutes to preliminarily disperse the two resins. Silanized nano-SiO2 powder was slowly added to the mixer, and the speed was set to 1500 r / min for continued mixing for 5 minutes. During this period, the material state was observed to ensure that there was no dust flying, no obvious color difference, or no particle agglomeration. Finally, a uniform light gray premix was obtained.

[0032] Step C4: melt blending and granulation. First, preheat the SHJ-35 twin-screw extruder, set the feeding section temperature to 180°C, the compression section temperature to 190°C, the homogenization section temperature to 200°C, and the die temperature to 195°C, and preheat for 30 minutes until the temperatures of each section are stable; turn on the extruder and set the screw speed to 200 r / min; uniformly feed the premix into the hopper at a rate of 5 kg / h through the loss weight feeder, and ensure stable feeding to avoid uneven mixing caused by fluctuating feeding; after the material is melt blended, it is extruded from the die, with a diameter of 3 ± 0.5 mm, and immediately enters a 25 ± 2°C cooling water tank for cooling and shaping, with a cooling length of 3 m to ensure complete solidification; the cooled material is sent to a drying machine to remove surface moisture, and then sent to a cutting machine at a speed of 300 r / min to cut into granules, obtaining modified thermoplastic polyurethane elastomer particles with a length of 3 ± 0.5 mm, which are sealed and packaged and stored in a dry place.

[0033] Preparation Example 2

[0034] Referring to Figure 1 As shown in FIG. 1, a modified thermoplastic polyurethane elastomer, which is functionally focused on improving the surface layer thickness stability of the functional layer of a CMP polishing pad, solves the problem of surface layer thickness deviation caused by uneven material shrinkage in the prior art by enhancing the rigidity of the matrix and the dispersibility of the nano filler, and is particularly suitable for high-precision polishing of wafer edges.

[0035] The difference between this preparation example and Preparation Example 1 is that:

[0036] The material ratio is different. The amount of polyether thermoplastic polyurethane is 90 parts, which is 5 parts more than that of Preparation Example 1, the amount of ethylene-vinyl acetate copolymer is 5 parts, which is 5 parts less than that of Preparation Example 1, the rigidity of the matrix is enhanced by increasing the proportion of TPU, and the shrinkage after foaming caused by excessive EVA is reduced. The amount of silane coupling agent KH-570 is 0.8 parts, which is 0.3 parts more than that of Preparation Example 1 based on the weight of nano SiO2, which strengthens the surface modification of nano SiO2 and improves its dispersibility in the TPU matrix.

[0037] The performance of silanized nano SiO2 is different. FTIR detection shows that the Si-O-C characteristic peak of silanized nano SiO2 in this preparation example is 1160 cm -1 The intensity ratio is 1.3, which is higher than 1.0 of Preparation Example 1, and the surface hydroxyl conversion rate reaches 90%. Scanning electron microscopy observation shows that the dispersed particle size is 70-90 nm, while that of Preparation Example 1 is 80-100 nm, and the agglomeration rate is <3%, which means that more uniform dispersion can reduce the surface layer thickness fluctuation caused by local agglomeration.

[0038] The modified thermoplastic polyurethane elastomer has different properties. The Shore hardness is 68±1 HD, the tensile strength is 42±2 MPa, and the rigidity is improved to inhibit the shrinkage deformation after foaming. The elongation at break is 420±30%, and the moderate reduction in flexibility can reduce the tensile deformation of the functional layer during subsequent processing, further ensuring the thickness accuracy of the surface layer.

[0039] Preparation Example 3

[0040] Referring to Figure 1 As shown in the figure, a modified thermoplastic polyurethane elastomer, which is focused on optimizing the cell structure uniformity of the functional layer of the CMP polishing pad, solves the problem of wide cell size distribution and large local density difference in the prior art by adjusting the flexibility of the matrix and the activity of the nano-nucleating agent, and is especially suitable for scenes with high requirements for polishing liquid transmission efficiency and wear consistency.

[0041] The difference between the present preparation example and Preparation Example 1 is that:

[0042] The preparation material ratio is different. The amount of polyether type thermoplastic polyurethane is 80 parts, which is reduced by 5 parts compared with Preparation Example 1, the amount of ethylene-vinyl acetate copolymer is 15 parts, which is increased by 5 parts compared with Preparation Example 1, the flexibility of the matrix is enhanced by increasing the proportion of EVA, and the probability of cell rupture is reduced. The amount of silane coupling agent KH-570 is 0.5 parts, but the silanization reaction condition is adjusted to 80°C / 1 hour to obtain more active nucleation sites.

[0043] The properties of silanized nano-SiO2 are different. According to FTIR detection, the Si-O-C characteristic peak of silanized nano-SiO2 in the present preparation example is 1160 cm -1 The intensity ratio is 1.1, which is lower than 1.0 of Preparation Example 1, but the Si-OH characteristic peak of 3400 cm -1 The intensity is significantly reduced, indicating that more surface hydroxyl groups are converted into active siloxane groups. Thermogravimetric analysis shows that the weight loss rate at 200°C is 3.2%, which is attributed to more organic groups introduced by high temperature treatment. These groups can promote the heterogeneous nucleation of CO2 gas during the foaming process.

[0044] The modified thermoplastic polyurethane elastomer has different properties. The Shore hardness is 62±1 HD, the elongation at break is 530±30%, and the higher flexibility can buffer the stress concentration during foaming, reducing the formation of large cells. Differential scanning calorimetry shows that the glass transition temperature of the elastomer is -28°C, and the lower glass transition temperature makes the matrix flow better at the foaming temperature, which is beneficial to the uniform growth of cells.

[0045] Example 1

[0046] Referring to Figure 2As shown, a CMP polishing pad with semi-continuous preparation of surface thickness, comprising a substrate layer and a functional layer thereon, with a total thickness of 1.25 mm, wherein the thickness ratio of the substrate layer and the functional layer is 4:1.

[0047] In this embodiment, the average thickness of the substrate layer is 1.0 mm, and the preparation material includes 100 parts of recycled polyurethane particles by weight ratio, with a hardness of 75±5 HD and an average density of 0.95 g / cm 3 The material is obtained from the cutting scraps of polishing pads from the Hefei factory of Anhui Heshen New Material Co., Ltd., and is recycled after crushing and granulation. The substrate layer serves as the supporting framework of the polishing pad, providing mechanical support and elastic resilience, and enhancing the bonding force with the functional layer through surface activation treatment.

[0048] In this embodiment, the average thickness of the functional layer is 0.25 mm, and the preparation material includes 70 parts of modified thermoplastic polyurethane elastomer, 10 parts of thermal expansion microspheres, 0.5 parts of silanized nano-SiO2, and 1 part of silane coupling agent KH-550 by weight ratio. The functional layer has a closed porosity of 92% and an average cell size of 28±2.2 microns, and is responsible for polishing liquid storage and nanoscale grinding function. The materials are all certified products from the supplier directory of Heshen. The modified thermoplastic polyurethane elastomer is prepared by the method of Preparation Example 1 to ensure the shaping ability and uniformity of cell nucleation of the functional layer matrix. The thermal expansion microspheres are of the commercially available type EXPANCEL 03DU80, which has no significant viscosity fluctuation in the torque rheometer test with the modified thermoplastic polyurethane elastomer.

[0049] A production process for semi-continuous preparation of CMP polishing pad with surface thickness, comprising the following steps:

[0050] Step S1: Regeneration treatment of substrate. The cutting scraps of existing polishing pads are crushed to a particle size of ≤5 mm in a jaw crusher, and impurities are removed through a 20-mesh sieve. The crushed material is placed in an alkali washing tank with 5wt% NaOH solution, stirred at 60°C for 30 minutes, and then dried in a 80°C vacuum drying oven for 4 hours after centrifugal dewatering. The dried crushed material is melted and granulated by SHJ-65 double-screw extruder at a speed of 150 r / min, to obtain recycled polyurethane particles. The particles are calendered into a 1.0 mm thick roll by YJ-600 calender at 80°C. The substrate roll is continuously conveyed to a plasma treatment machine, and a mixture of Ar / O2 with a volume ratio of 4:1 is introduced at a total gas flow rate of 250 sccm. The treatment power is set to 300 W, and the treatment is continued for 5 minutes to remove the weak boundary layer on the surface of the substrate. A suspension of nano-alumina with a mass fraction of 8% is sprayed on the surface of the substrate after plasma cleaning, and etched for 10 minutes. The surface is then rinsed with deionized water to remove the residual suspension, and then dried. The surface roughness Ra of the treated substrate is detected by a stylus roughness meter, and should reach 3.2±0.3 microns to enhance the mechanical engagement ability with the subsequent functional layer.

[0051] Step S2: functional layer slurry coating. Start the high-speed disperser, set the speed to 1000 r / min, add 70 parts of modified thermoplastic polyurethane elastomer particles of Preparation Example 1, 10 parts of thermally expandable microspheres, and 0.5 parts of silanized nano-SiO2 successively, after the addition of the materials is completed, maintain the speed at 1000 r / min, dry mix for 5 minutes, after the dry mixing is completed, slowly add 1 part of KH-550 coupling agent and an appropriate amount of DMF solvent, control the amount of solvent added to make the solid content of the slurry reach 60%, measure the viscosity of the slurry at 25°C using a Brookfield viscometer, adjust the viscosity to 1500±100 cP by adding solvent or adjusting the material ratio, maintain the speed at 1000 r / min, continue to disperse for 30 minutes until there is no particle agglomeration in the slurry, start the slot coater, preheat to working temperature, adjust the die gap to 150 microns, set the coating width to 650 millimeters, send the substrate web through the tension control system to the coating machine inlet at a tension of 50 N, set the web transmission speed to 2 m / min, start the slurry delivery pump, and uniformly deliver the prepared slurry to the slot die, adjust the flow of the pump to ensure that the slurry forms a uniform liquid film at the die outlet, immediately after coating, use a beta-ray thickness gauge to detect the wet film thickness, the accuracy of the thickness gauge is ±2 microns, the measured value is about 500 microns, the beta-ray thickness gauge transmits real-time detection data to the PLC control system, automatically calculates and adjusts the die pressure adjustment range to 0.2-0.3 MPa, ensures that the dry film thickness after pre-drying is stable at 0.25±0.02 millimeters, start the hot air tunnel, set the temperature to 60°C, the tunnel length is 5 m, the coated web passes through the hot air tunnel at a speed of 2 m / min, the drying time is 3 minutes, sample the dried web, use a gas chromatograph to detect the solvent residue, ensure that the solvent residue ≤0.5%, if it exceeds the standard, adjust the hot air temperature or transmission speed.

[0052] Step S3: Step foaming shaping. First, supercritical CO2 penetration is performed. The pre-dried roll is continuously sent into the GCF-50 autoclave at a conveying speed of 0.5 m / min. After checking the equipment sealing performance and sensor state, the CO2 gas source is opened to increase the pressure to 5 MPa at a rate of 0.5 MPa / min, and the temperature is increased to 40°C. The pressure and temperature are maintained for 20 minutes to ensure that CO2 is fully dissolved and penetrated into the functional layer to 8 wt%. The pressure fluctuation during the whole process is controlled within ±0.1 MPa. Then, N2 sealing and rapid cooling are performed. The CO2 is slowly released at a rate of 0.1 MPa / min until the pressure drops to 2 MPa. High-purity N2 with a purity of ≥99.9% is introduced to maintain the pressure. At the same time, the liquid nitrogen spraying system is started. The temperature in the autoclave is reduced to -30°C at a rate of 10°C / min and maintained for 10 minutes. Rapid cooling forms a dense layer with a thickness of 50±5 microns on the surface of the functional layer to prevent internal gas from escaping. Finally, gradient heating foaming is performed. The three-stage foaming oven is preheated to 50°C, 80°C and 120°C. The roll after rapid cooling is uniformly passed through the foaming oven at a speed of 0.3 m / min. The microspheres are initially softened at 50°C for 5 minutes, start to expand at 80°C for 5 minutes, and completely expand at 120°C for 15 minutes. The temperature is adjusted to ensure that the closed cell rate reaches 92%. After foaming, random sampling is performed. Scanning electron microscopy is used to observe and verify that the cell size distribution is within the range of 5-45 microns.

[0053] Step S4: Laser microprocessing. First, start the sander of MM2015 to lightly grind the surface of the foamed roll at a pressure of 0.2 MPa and a conveying speed of 1 m / min, remove a thickness of 0.01 mm in total, and detect with a laser flatness instrument to ensure that the flatness is ≤5 microns; then start the 1030 nm femtosecond laser, preheat for 15 minutes, set the spiral groove parameters through the EZCAD2.1 laser engraving software, including depth 50 microns, width 30 microns, pitch 200 microns, spiral angle 45°, scanning speed 1000 mm / s, power 10 W, pulse frequency 500 kHz, filling interval 10 microns, fix the roll on the laser processing workbench, adjust the workbench height to make the roll surface coincide with the laser focal point, then start the laser engraving program to start spiral groove engraving, observe the groove forming situation in real time through the microscope during the engraving process to ensure that there is no ablation, edge collapse and other defects; after engraving, turn off the laser, randomly select 5 detection points with a 500 times microscope, measure the groove depth and width, wherein the depth allowable deviation is ±2 microns, the width allowable deviation is ±1 micron, then use a three-dimensional profilometer to detect the groove pitch and spiral angle accuracy, set the measurement range to cover 5 complete pitches, the sampling point density is 100 points / mm, after analyzing the measurement data, the pitch deviation is required to be ≤±5 microns, the spiral angle deviation is required to be ≤±0.5°; if the detection result exceeds the allowable range, adjust the laser parameters and repeat the above operation until the standard is met. When operating, special protective glasses with a wavelength of 1030 nm should be worn, the processing environment should be kept clean during the engraving process to avoid dust affecting the processing precision, and the laser light path system should be cleaned regularly to ensure the quality of laser output.

[0054] Step S5: Sorting detection. Use a laser thickness gauge to scan the polished pad thickness at 5mm intervals full width, ensure the total thickness is 1.25mm and the deviation is within ±0.02mm, mark the out-of-tolerance area, if the single roll has more than 3 unqualified points, the whole roll is judged as waste; start the machine vision system with a resolution of 10 microns, scan the surface row by row at a speed of 0.5m / s, analyze the cell size distribution through the algorithm, and ensure that the range is ≤7.8%; turn on the 800lux optical detection system, detect at a speed of 1m / s, allow a single sheet to have 0-1 bubbles with a diameter ≤0.5mm or scratches with a length ≤2mm, and judge as waste if the amount exceeds; the qualified roll is transmitted to the slitting station, and the unqualified product is rejected to the waste area; start the FQ-650 circular knife slitting machine, set the cutter speed to 3000r / min, the feeding speed to 5m / min, adjust the mold to Φ600mm specification, control the cutter position accuracy ±0.1mm through the servo motor, monitor the edge quality during slitting, and automatically stop and alarm when abnormal; use a laser profiler to take point detection every 30° on the edge of the slitted round pad, ensure that the edge diameter deviation is ±0.5mm and the roundness error is ≤0.3mm; the qualified round pad is sleeved into a PE plastic film by a mechanical arm, and after heat sealing at 180℃, it is stacked on a tray according to the batch and stored in a warehouse with humidity ≤50% and temperature 23±2℃.

[0055] Example 2

[0056] Referring to Figure 2 A CMP polishing pad prepared by semi-continuous surface thickness, comprising a substrate layer and a functional layer thereon, with a total thickness of 1.25mm, wherein the thickness ratio of the substrate layer and the functional layer is 4:1.

[0057] In this embodiment, the substrate layer is completely consistent with example 1, both of which use 100 parts of recycled polyurethane particles, which are broken, granulated and calendered into 1.0mm thick roll, with a surface roughness Ra of 3.2±0.3 microns, ensuring that the functional layer material is the only variable and excluding the interference of the substrate on the performance.

[0058] In this embodiment, 70 parts of modified thermoplastic polyurethane elastomer of the functional layer uses the particles of preparation example 2, and the model and amount of the remaining materials are completely consistent with example 1. The dry film thickness precision of the functional layer is improved to 0.25±0.015mm, the closed cell rate is 92% consistent with example 1, but the cell size distribution is more concentrated in 10-40 microns, and the shore hardness of the functional layer is 68±1HD, and the tensile strength is 42±2MPa.

[0059] This embodiment focuses on solving the problem of wafer edge over-polishing and short service life of polishing pad in the prior art by using high-rigidity modified TPU of preparation example 2, and is suitable for edge planarization polishing of 12-inch large-size wafers. The difference between the preparation steps of this embodiment and example 1 is that:

[0060] In step S2, during the coating of the functional layer slurry, because the modified thermoplastic polyurethane elastomer of Preparation Example 2 has a higher hardness, the dry mixing time needs to be extended by 1 minute to ensure uniform contact between the particles and the thermally expanded microspheres and SiO2. The melt viscosity of the modified thermoplastic polyurethane elastomer of Preparation Example 2 is slightly higher, so the amount of DMF solvent needs to be increased by 2% compared with Example 1 to ensure that the viscosity is stable at 1500±100cP. Due to the increased rigidity of the functional layer material, the adjustment accuracy of the PLC system for the die head pressure needs to be increased to ±0.005MPa to avoid edge thickness deviation caused by pressure fluctuations.

[0061] Example 3

[0062] Reference Figure 2 As shown, a CMP polishing pad with a semi-continuous surface thickness preparation includes a substrate layer and a functional layer thereon, with a total thickness of 1.25 mm, wherein the thickness ratio of the substrate layer to the functional layer is 4:1.

[0063] In this embodiment, the substrate layer is consistent with that in Example 1, using 100 parts of recycled polyurethane particles, which are crushed, granulated, and calendered into a 1.0 mm thick roll material with a surface roughness Ra of 3.2 ± 0.3 micrometers, ensuring that the change in the functional layer material is the only variable.

[0064] In this embodiment, the 70 parts of modified thermoplastic polyurethane elastomer in the functional layer are the particles of Preparation Example 3. The dry film thickness of the functional layer is accurate to 0.25±0.02 mm, the closed cell rate is 92%, but the cell size distribution is more concentrated in 15-35 micrometers. The Shore hardness of the functional layer is 62±1HD, and the elongation at break is 530±30%.

[0065] This embodiment, through the preparation of the highly flexible modified TPU of Example 3, focuses on solving the problems of uneven polishing slurry transport and excessively rapid local wear caused by the wide pore size distribution in the prior art. It is suitable for wafer polishing scenarios at 3nm and below nodes where high polishing rate stability and material removal uniformity are required. The preparation steps differ from those of Example 1 in that:

[0066] In step S2, the modified thermoplastic polyurethane elastomer of Preparation Example 3 has higher flexibility and stronger adhesion to the thermally expanded microspheres, so the dry mixing time can be shortened by 1 minute to avoid over-mixing and damage to the microspheres. The melt viscosity of the modified thermoplastic polyurethane elastomer of Preparation Example 3 is slightly lower, so the amount of DMF solvent needs to be reduced by 2% compared with Example 1 to ensure that the viscosity is stable at 1500±100cP.

[0067] In the step S3 of the step foaming and shaping, the matrix of the modified thermoplastic polyurethane elastomer of the preparation example 3 has high flexibility, the CO2dissolution rate is faster, the penetration time can be shortened from 20 minutes of the example 1 to 15 minutes, the pressure is still maintained at 5 MPa, and the CO2solubility is ensured to reach 8 wt%; the modified thermoplastic polyurethane elastomer of the preparation example 3 has a lower glass transition temperature, and the heating rate can be increased to 3 ℃ / min, so that the bubble coalescence caused by slow heating is avoided, and the uniformity of the bubble size is ensured.

[0068] Comparative example 1

[0069] A CMP polishing pad with semi-continuous preparation of surface thickness, in order to verify the necessity of the modified thermoplastic polyurethane elastomer for the surface layer thickness and the uniformity of the bubble, which is different from example 1 in that the unmodified thermoplastic polyurethane elastomer is used instead of the modified thermoplastic polyurethane elastomer of the preparation example 1, and the rest of the materials and processes are the same as example 1.

[0070] Comparative example 2

[0071] A CMP polishing pad with semi-continuous preparation of surface thickness, in order to verify the dispersion effect of silanized nano-SiO2, which is different from example 1 in that the un-silanized nano-SiO2 is used instead of the silanized product of the preparation example 1, and the rest of the materials and processes are the same as example 1.

[0072] Comparative example 3

[0073] A CMP polishing pad with semi-continuous preparation of surface thickness, in order to verify the necessity of the step foaming and shaping process, which is different from example 1 in that a single CO2 O2 Foaming and canceling N2sealing and quenching, the rest of the materials and processes are the same as example 1, in the step S3 of the step foaming and shaping, 5 MPa of CO2is introduced into the autoclave, and after 40 ℃ holding for 20 minutes, the temperature is directly increased to 120 ℃ for foaming, without N2sealing and-30 ℃ quenching.

[0074] Performance test

[0075] Test example 1

[0076] Surface layer thickness and uniformity test. The test object is the functional layer of the polishing pad of examples 1-3 and comparative examples 1-3, and the test content includes average thickness, thickness deviation and edge and center thickness difference. The test uses GB / T6672-2001 "Plastic film and sheet thickness determination mechanical measurement method", combined with laser thickness gauge: 20 test points are randomly selected on the surface of the polishing pad, the thickness of each point is read by the laser thickness gauge, the average thickness, thickness deviation and the maximum thickness difference of the edge and center are calculated, to evaluate the uniformity and stability of the functional layer thickness, and the test results are shown in table 1.

[0077] Test example 2

[0078] Cellular structure parameter test. The test object is the functional layer cross-section of the polishing pad of Examples 1-3 and Comparative Examples 1-3, and the test content covers average cell size, cell size range, cell density and closed cell rate. The test refers to GB / T10799-2008 "Determination of Open and Closed Cell Volume Fraction of Rigid Foamed Plastics", combined with scanning electron microscope observation method: the polishing pad is sliced along the thickness direction and gold sprayed, the cross-section cells are observed under SEM magnification of 500 times, 5 fields of view are randomly selected, the cell size and density are counted by image analysis software, and the range is calculated; the closed cell rate is calculated by the ratio of closed cell volume to total pore volume to represent the uniformity and integrity of the cell structure, and the test results are shown in Table 1.

[0079] Test Example 3

[0080] Polishing rate and uniformity test. The test object is the polishing pad of Examples 1-3 and Comparative Examples 1-3, and the test content is the copper film polishing rate and polishing rate fluctuation. The test refers to SEMIF13-95 "Polishing Pad Specification", combined with the actual wafer polishing process: using a CMP polisher, an 8-inch copper plated film wafer is used as the polishing object, the polishing conditions are set as pressure 3 psi, rotation speed 90 r / min, polishing liquid acidic copper polishing liquid, flow rate 200 mL / min, polishing time 60 s; the thickness difference of the wafer before and after polishing is measured by an ellipsometer to calculate the polishing rate; 9 test points are selected, the rate fluctuation value is calculated by the deviation of each point rate from the average rate to evaluate the polishing efficiency and stability, and the test results are shown in Table 1.

[0081] Test Example 4

[0082] Wafer surface defect rate test. The test object is the copper wafer polished by Test Example 3, and the test content is the number of defects such as surface scratches and pits. The test refers to SEMIM40-03 "Wafer Surface Defect Classification and Counting Standard", and a wafer surface detector is used to scan the entire surface of the polished wafer to count the total number of defects with a size of ≥0.5 microns to represent the influence of the polishing pad on the wafer surface quality, and the test results are shown in Table 1.

[0083] Test Example 5

[0084] Wear resistance and service life test. The test object is the polishing pad of Examples 1-3 and Comparative Examples 1-3, and the test content is the weight loss rate after polishing 5 wafers and the effective service life. The test uses the industry general accelerated wear test method: 5 8-inch copper wafers are polished in succession by the same polishing pad, the weight difference before and after polishing is weighed to calculate the weight loss rate; the total number of polished wafers is recorded when the polishing rate decreases to 80% of the initial value, which is the effective service life, to evaluate the wear resistance and economy of the polishing pad, and the test results are shown in Table 1.

[0085] Test item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Average thickness (mm) 0.25 0.25 0.25 0.25 0.25 0.25 Thickness deviation (± mm) 0.02 0.015 0.02 0.08 0.06 0.07 Edge-center thickness difference (mm) 0.02 0.01 0.02 0.09 0.07 0.08 Average cell size (microns) 28±2.2 30±1.8 26±1.5 45±15 35±12 40±10 Cell size range (%) 7.8 8.2 7.2 22.0 18.0 25.0 Cellular density (cells / mm 2 )]]> 520 520 550 320 380 350 Closed cell rate (%) 92 92 93 70 75 78 Polishing rate (A / min) 7620±280 7580±240 7850±210 6200±550 6500±480 6300±520 Rate fluctuation (± %) 3.7 3.2 2.7 8.9 7.4 8.3 Wafer defect rate (pieces) 1 0 0 8 10 6 Weight loss rate after 5 pieces of wafer (%) 2.1 1.8 2.3 5.8 4.5 5.2 Effective service life (pieces) 5 6 5 2 3 2

[0086] Table 1

[0087] Data analysis and conclusion

[0088] Surface layer thickness and uniformity analysis. The surface layer thickness precision is the core index affecting the wafer polishing uniformity, which is directly related to the pressure distribution during polishing. From the test results, the thickness deviation of examples 1-3 is controlled within 0.015-0.02 mm, and the thickness difference between the edge and the center is ≤0.02 mm, which is significantly better than comparative examples 1-3. Among them, example 2 performs best, which is directly related to the increase of the proportion of modified thermoplastic polyurethane elastomer in preparation example 2, which enhances the rigidity of the matrix. High-rigidity modified thermoplastic polyurethane elastomer can inhibit the shrinkage deformation after foaming, and cooperate with high-dispersed silanized SiO2 to reduce local protrusions, thereby improving the thickness stability. The thickness precision of example 1 and example 3 is equivalent, which shows that the basic formula and the high flexibility formula can meet the high precision requirement, and only the edge control is slightly inferior to example 2. Comparative example 1 lacks the flexibility adjustment of ethylene-vinyl acetate copolymer and the nucleation support of SiO2, and the shrinkage after foaming is uneven, with a thickness deviation of ±0.08 mm. Comparative example 3 lacks the protection of the dense layer in the surface layer, and the gas escape leads to the intensification of the surface layer thickness fluctuation, which verifies the necessity of the rapid cooling and gas locking process in the step-by-step foaming and shaping.

[0089] Cell structure parameter analysis. The uniformity of cell structure determines the polishing liquid transmission efficiency and material removal consistency, mainly reflected in the cell size distribution, density and closed cell rate. The cell size range of examples 1-3 is only 7.2%-8.2%, the average cell size deviation is ≤±2.2 microns, the cell density is ≥510 per square millimeter, and the closed cell rate is ≥92%, which is much better than the comparative examples. Among them, example 3 performs best, which is attributed to the high flexibility design of preparation example 3. 15 parts of ethylene-vinyl acetate copolymer improve the matrix fluidity, cooperate with 80℃ / 1 hour silanization treatment of SiO2, more active siloxane groups promote uniform nucleation of CO2, and reduce the formation of large pores; the lower glass transition temperature makes the cell growth more synchronous during the foaming process, further reducing the size difference. The cell uniformity of examples 1 and 2 is slightly inferior to example 3, but still much higher than the comparative examples, which shows that 10 parts of ethylene-vinyl acetate copolymer and silanized SiO2 in the basic formula can effectively solve the defect of wide cell distribution in the prior art; comparative example 2 forms stress concentration area around the agglomerates due to the agglomeration of nano-SiO2, resulting in local large pores, with a cell range of 18%; comparative example 3 forms large pores due to the rapid escape of CO2 in the surface layer without N2 sealing, and the core layer has fine and dense cells, with a cell range of 25%, which verifies the key role of silane modification and step-by-step foaming in cell uniformity.

[0090] Polishing performance analysis. Polishing rate and stability, wafer defect rate directly reflect the practical value of polishing pad, the polishing rate of examples 1-3 reaches 7580-7850 Å / min, the rate fluctuation is only 2.7%-3.7%, the wafer defect rate is ≤1 piece, which is significantly better than the comparative examples. Among them, the polishing rate of example 3 is the highest, and the fluctuation is the smallest, because its narrow distribution of pores can uniformly transmit polishing liquid, combined with high closed porosity to reduce the loss of polishing liquid, to realize stable material removal; low hardness and high elongation at break can buffer the polishing pressure and reduce scratches. Example 2 has more uniform edge pressure distribution due to high rigid thermoplastic polyurethane elastomer and dense surface layer, especially suitable for edge polishing of 12-inch large-size wafers. Comparative example 1 has a polishing liquid transmission blockage due to sparse and uneven thickness of pores, and the rate fluctuation reaches 8.9%; Comparative example 2 has a high defect rate of 10 pieces due to SiO2 agglomerates scratching the wafer, which verifies the decisive influence of modified thermoplastic polyurethane elastomer and silanized SiO2 on polishing quality.

[0091] Wear resistance and service life analysis. Wear resistance is directly related to the economy of polishing pad, reflecting the material wear resistance and structural stability, the weight loss rate of 5 wafers of examples 1-3 is only 1.8%-2.3%, and the effective service life reaches 5-6 pieces, which is more than twice that of the comparative examples. Example 2 has the longest service life, thanks to the synergistic effect of high tensile strength thermoplastic polyurethane elastomer in preparation example 2 and highly dispersed SiO2. SiO2 as a reinforcing phase improves wear resistance, and high rigidity matrix reduces local deformation, thereby delaying wear. Although the hardness of example 3 is lower, the uniform pore structure makes the wear more synchronous, and the weight loss rate is 2.3%, the service life still reaches 5 pieces, which proves the importance of pore uniformity to wear resistance. Comparative example 1 has a local wear too fast due to loose pore structure, and the weight loss rate is 5.8% after 5 pieces; Comparative example 3 has a surface layer macropore easy to collapse, and the service life is only 2 pieces, which verifies the necessity of material formula optimization and process setting for prolonging the service life.

[0092] The technical scope of the present application is not limited to the content in the above description, and those skilled in the art can make various modifications and modifications to the above examples without departing from the technical idea of the present application, and these modifications and modifications should all belong to the protection scope of the present application.

Claims

1. A CMP polishing pad with a semi-continuous surface thickness preparation, characterized in that, The system comprises a substrate layer and a functional layer thereon. The materials used to prepare the functional layer include, by weight, 65-75 parts of modified thermoplastic polyurethane elastomer, 8-12 parts of thermally expandable microspheres, 0.3-0.7 parts of silanized nano-silica, and 0.8-1.2 parts of silane coupling agent KH-550. The materials used to prepare the modified thermoplastic polyurethane elastomer include, by weight, 80-90 parts of polyether-type thermoplastic polyurethane, 5-15 parts of ethylene-vinyl acetate copolymer, and silanized nano-SiO2, which are melt-blended together. By controlling the ratio of thermoplastic polyurethane to ethylene-vinyl acetate copolymer and the dispersibility of nanofillers, combined with the semi-continuous coating and stepwise foaming process of the functional layer, high-precision control of surface thickness and uniform distribution of cell structure are achieved. The stepwise foaming process includes sequential supercritical CO2 infiltration, N2 sealing and low-temperature rapid cooling and gas locking, and gradient heating foaming steps.

2. The CMP polishing pad with semi-continuous surface thickness preparation according to claim 1, characterized in that: The substrate layer is prepared using recycled polyurethane particles, comprising 100 parts by weight of recycled polyurethane particles. These recycled polyurethane particles are derived from polishing pad scraps, which are crushed, granulated, and then recycled.

3. The CMP polishing pad with semi-continuous surface thickness preparation according to claim 1, characterized in that: The modified thermoplastic polyurethane elastomer contains 90 parts of polyether-type thermoplastic polyurethane and 5 parts of ethylene-vinyl acetate copolymer. The functional layer focuses on improving the surface thickness stability and wear resistance. The functional layer has a Shore hardness of 67-69 degrees and a tensile strength of 41-43 MPa. It is suitable for edge planarization and polishing of large-size wafers, with a thickness difference between the edge and the center ≤0.01 mm.

4. The CMP polishing pad with semi-continuous surface thickness preparation according to claim 1, characterized in that: In the modified thermoplastic polyurethane elastomer, the weight ratio of thermoplastic polyurethane to ethylene-vinyl acetate copolymer is 16:

3. The functional layer focuses on optimizing the cell size distribution and the uniformity of polishing fluid transmission. The functional layer has a Shore hardness of 61-63 degrees and an elongation at break of 500-560%, making it suitable for high-precision node wafer polishing scenarios. The cell size distribution is concentrated in the range of 15-35 micrometers.

5. The CMP polishing pad with semi-continuous surface thickness preparation according to claim 1, characterized in that: The thickness ratio of the substrate layer to the functional layer is 4:1, with a total thickness of 1.25 mm. The functional layer has a closed-cell rate of ≥92% and an average cell density of ≥510 cells / mm². The substrate layer and the functional layer work together to achieve uniform pressure transmission and efficient storage and transmission of polishing fluid.

6. A CMP polishing pad manufacturing process for semi-continuous surface thickness preparation, used to prepare the CMP polishing pad as described in any one of claims 1-5, characterized in that: Includes the following steps: S1: Substrate regeneration process, the polishing pad scraps are crushed, sieved, cleaned and dried, then melted and granulated, rolled into rolls and subjected to surface activation treatment of plasma cleaning and nano-alumina etching. S2: Functional layer slurry coating, the modified thermoplastic polyurethane elastomer, thermal expansion microspheres, silanized nano SiO2 and coupling agent are mixed, solvent is added to prepare slurry, and the slurry is coated on the surface of the substrate layer by a slot coater, and the dry film thickness is controlled by drying. S3: Stepwise foaming and shaping, sequentially supercritical CO2 infiltration, N2 sealing and low-temperature rapid cooling and gas locking, and then gradient heating foaming to form a closed-cell structure; S4: Laser micromachining, the surface of the foamed functional layer is sanded and smoothed, and then a femtosecond laser is used to carve spiral grooves. S5: Sorting, inspection, cutting and packaging. The polishing pads are inspected for thickness, cell structure and surface defects. After passing the inspection, they are cut into the specified specifications and packaged.

7. The CMP polishing pad manufacturing process for semi-continuous surface thickness preparation according to claim 6, characterized in that: The modified thermoplastic polyurethane elastomer is mainly prepared by the following methods: C1: Raw material pretreatment: Polyether-type thermoplastic polyurethane and ethylene-vinyl acetate copolymer are sieved and dried respectively, and nano-SiO2 is vacuum dried to remove surface adsorbed water; C2: Preparation of silanized nano-SiO2: Nano-SiO2 is dispersed in an ethanol-water mixture, a silane coupling agent is added and reacted, and then centrifuged, washed and dried to obtain silanized nano-SiO2; C3: Premix preparation, which involves uniformly mixing dried polyether-type thermoplastic polyurethane, ethylene-vinyl acetate copolymer, and silanized nano-SiO2. C4: Melt blending and granulation. The premixed material is melt-blended in a twin-screw extruder, then extruded, cooled, and pelletized to obtain modified thermoplastic polyurethane elastomer granules.

8. The CMP polishing pad manufacturing process for semi-continuous surface thickness preparation according to claim 6, characterized in that: During the functional layer slurry coating process, for scenarios that emphasize improving the stability of surface layer thickness, the dry mixing time is extended by 1-2 minutes to ensure uniform contact between the high-rigidity modified thermoplastic polyurethane elastomer and other components; the solvent dosage is increased by 1-3% to adapt to the high-viscosity matrix and maintain the slurry viscosity at 1400-1600 cP; the die head pressure adjustment accuracy is improved to 0.005 MPa, and the edge thickness deviation is reduced by precisely controlling the coating pressure to adapt to the edge planarization and polishing requirements of large-size wafers.

9. The CMP polishing pad manufacturing process for semi-continuous surface thickness preparation according to claim 6, characterized in that: In the step-by-step foaming and shaping process, for scenarios that focus on optimizing the cell size distribution, the supercritical CO2 permeation time is shortened to 12-18 minutes. The high gas solubility of the highly flexible modified thermoplastic polyurethane elastomer is used to ensure full permeation. In the gradient heating stage, the heating rate is increased to 2-4℃ / minute. By accelerating the heating rate, cell merging is reduced. Combined with parameter control within the target cell size range of 15-35 micrometers, the uniformity of polishing fluid transmission is improved, adapting to the high-precision node wafer polishing requirements.

10. The CMP polishing pad manufacturing process for semi-continuous surface thickness preparation according to claim 6, characterized in that: The substrate roll after the substrate regeneration treatment is directly and continuously fed into the functional layer slurry coating process through the transfer roller group. The coated roll is directly and continuously fed into the step-by-step foaming and shaping process through the transition transfer structure. The foamed and shaped roll continues to be continuously transferred to the laser micromachining process through the same transfer path. The micromachined roll is directly transferred to the sorting and inspection stage. The processes are coordinated and matched to achieve uninterrupted flow.

Images