A reverse etch open hole polishing pad, its preparation method and use

Abstract

The application provides a reverse-dissolution opening polishing pad, a preparation method and use thereof, and the preparation method comprises the following steps: soaking a non-woven fabric base cloth in an impregnation solution containing polyurethane resin to obtain a base cloth containing polyurethane resin; immersing the base cloth containing polyurethane resin into a first solution for coagulation treatment; cleaning the coagulated base cloth with a second solution; and sequentially performing pre-drying, gradient drying and polishing on the cleaned base cloth to obtain a polishing pad; the first solution and the second solution are aqueous solutions containing DMF, the concentration of DMF in the liquid squeezed from the cleaned base cloth is 3-15 wt%, the temperature of the pre-drying is 80-100 DEG C, and the temperature of the gradient drying is 130-180 DEG C. The polishing pad prepared by the method has a loose and porous structure, high air permeability and high water retention, has a good polishing rate in the polishing process, and the surface quality of the silicon wafer after polishing is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of polishing pad preparation technology, and in particular to an anti-dissolved open-pore polishing pad, its preparation method, and its uses. Background Technology

[0002] Polishing pads are a core consumable in chemical mechanical planarization (CMP) processes, and their performance directly affects the overall planarization effect, defect control level, and process stability of the wafer surface. Polishing pads are typically manufactured from porous polymer materials (such as polyurethane) using specific processes. Their core functions are to store and uniformly deliver polishing fluid, provide appropriate mechanical friction, promptly remove reaction byproducts and wear debris, and maintain a stable polishing interface environment. Therefore, the microstructure design of the polishing pad, especially its pore characteristics (such as porosity, pore size distribution, and pore connectivity), has a decisive influence on polishing performance.

[0003] Among the performance parameters of polishing pads, air permeability and retention capacity are two key and interrelated indicators. Air permeability mainly reflects the connectivity of the pores inside the polishing pad and the gas passage capacity. High air permeability facilitates the rapid discharge of heat, gas, and fine debris generated during the polishing process, thereby reducing defects such as scratches and residues on the wafer surface and improving process stability and wafer surface quality. Retention capacity refers to the polishing pad's ability to store and retain polishing fluid. High retention capacity ensures a continuous and stable supply of fresh polishing fluid to the polishing interface during high-speed polishing, maintaining the uniformity and efficiency of the chemical reaction. This is crucial for obtaining uniform material removal rates, reducing corrosion, and achieving excellent planarization results.

[0004] Currently, polishing pads widely used in industry (such as bonded porous polyurethane pads) mainly introduce pores through foaming processes, filler-based pore formation, or machining. However, under existing technological conditions, the air permeability and oxygen retention capacity of polishing pads often exhibit a significant negative correlation or an inherent contradiction that is difficult to optimize simultaneously. This has become a technical bottleneck restricting further performance improvements in high-end CMP processes (especially for polishing wafers at advanced process nodes).

[0005] Therefore, how to overcome the limitations of existing polishing pad materials and structures and develop an innovative preparation method that can synergistically optimize and simultaneously obtain polishing pads with high air permeability and high nutrient content, so that during the polishing process, it can ensure a sufficient and stable supply of polishing fluid to achieve uniform material removal, and also ensure good heat dissipation and chip removal capabilities to obtain a defect-free, high-quality wafer surface, has become a key technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an anti-dissolving open-pore polishing pad, its preparation method and uses, to solve the problem that polishing pads in the prior art cannot simultaneously achieve high air permeability and high nutrient content.

[0007] To achieve the above and other related objectives, the present invention provides an anti-dissolving open-pore polishing pad, its preparation method, and its uses.

[0008] The first aspect of this invention provides a method for preparing an anti-dissolving open-pore polishing pad, the method comprising: immersing a nonwoven fabric base in an impregnation solution containing polyurethane resin to obtain a polyurethane resin-containing base fabric; immersing the polyurethane resin-containing base fabric in a first solution for coagulation treatment; cleaning the coagulated base fabric with a second solution; and sequentially pre-drying, gradient drying, and polishing the cleaned base fabric to obtain a polishing pad; wherein the first and second solutions are aqueous solutions containing DMF, the concentration of DMF in the liquid extruded from the cleaned base fabric is 3-15 wt%, the pre-drying temperature is 80-100°C, and the gradient drying temperature is 130-180°C.

[0009] Preferably, the solid content of polyurethane resin in the impregnation solution is 10~30wt%; for example, it can be 10wt%, 15wt%, 20wt%, 25wt%, or 30wt%.

[0010] Preferably, the solvent of the impregnation solution is DMF.

[0011] More preferably, the polyurethane resin is a liquid polyurethane resin, wherein the liquid is mainly a low-viscosity, uncured or partially reacted liquid polyurethane prepolymer or reactive component. The solid content in the impregnation liquid of the present invention refers to the percentage of solid polyurethane in the total weight of liquid polyurethane resin and solvent.

[0012] Preferably, the polyurethane resin is a thermoplastic polyurethane resin.

[0013] Preferably, the molecular weight of the polyurethane resin is 10,000 to 70,000 Da; for example, it can be 10,000 Da, 20,000 Da, 30,000 Da, 4,000 Da, 50,000 Da, 60,000 Da, or 70,000 Da.

[0014] Preferably, the modulus of the polyurethane resin is 8~30 MPa; for example, it can be 8 MPa, 10 MPa, 15 MPa, 20 MPa, 25 MPa, or 30 MPa. Polyurethane resins within this modulus range are elastomers, soft and easily deformable, and suitable for making polishing pads.

[0015] Preferably, the polyurethane resin molecular chain is composed of hard segments and soft segments, wherein the hard segments are formed by reacting diisocyanate and chain extender, and the soft segments are composed of polyols; the diisocyanate is selected from any one or more of diphenylmethane diisocyanate, toluene diisocyanate, terephthalic diisocyanate, and naphthalene-1,5-diisocyanate; the chain extender is selected from any one or more of 1,4-butanediol, ethylene glycol, hydroquinone-bis(2-hydroxyethyl) ether, and hydroquinone dihydroxyethyl ether; and the polyol is selected from any one or more of polybutanediol, polypropylene oxide, polyethylene oxide, polyadipate polyol, polycaprolactone, and polycarbonate polyol.

[0016] Preferably, the nonwoven fabric is a polyester fiber nonwoven fabric made by needle punching or hydroentangling processes.

[0017] Preferably, the fiber fineness of the nonwoven fabric is 2~10 dtex; for example, it can be 2dtex, 3dtex, 4dtex, 5dtex, 6dtex, 7dtex, 8dtex, 9dtex, or 10dtex.

[0018] More preferably, the nonwoven fabric has a fiber fineness of 2 to 5 dtex. Nonwoven fabrics within this fineness range can balance a certain degree of softness, strength, and functionality.

[0019] Preferably, the fiber length of the nonwoven fabric is 30-80mm; for example, it can be 30mm, 40mm, 50mm, 60mm, 70mm, or 80mm.

[0020] More preferably, the fiber length of the nonwoven fabric is 40-60 mm. Nonwoven fabrics with this fiber length have excellent web uniformity, moderate strength and softness, and a smooth surface appearance.

[0021] Preferably, the thickness of the nonwoven fabric is 1.8~2.2mm; for example, it can be 1.8mm, 1.9mm, 2.0mm, 2.1mm, or 2.2mm.

[0022] Preferably, the nonwoven fabric has a basis weight of 250~330 g / m². 2 For example, it can be 250 g / m³ 2 260 g / m 2 270g / m 2 280 g / m 2 290 g / m 2 300 g / m 2 310 g / m 2 320 g / m 2 330 g / m 2 .

[0023] More preferably, the basis weight of the nonwoven fabric is 300~330 g / m². 2 .

[0024] Preferably, the preparation method further includes squeezing the base fabric after soaking to remove excess impregnation liquid.

[0025] More preferably, the extrusion is performed by sequentially using pressure rollers and a rolling mill.

[0026] More preferably, the pressure roller extrusion is performed by using a pressure roller with a gap of 70-120% of the thickness of the nonwoven fabric to extrude / scrape off excess floating material on the surface. The pressure roller extrusion adopts a three-dip-three-roll process to ensure that the impregnation liquid is fully immersed in the nonwoven fabric.

[0027] Most preferably, in the three-dip-three-roll process, the time for a single immersion is 20 to 40 minutes; for example, it can be 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes.

[0028] More preferably, the temperature during the extrusion process in the rolling mill is 20~30℃.

[0029] More preferably, the pressure during the extrusion of the rolling mill is 1.5 to 2.5 bar.

[0030] More preferably, the rolling mill speed during extrusion is 1~2℃m / min.

[0031] Preferably, the mass ratio of polyurethane resin solids to nonwoven fabric base fabric in the impregnation solution is 1 to 3:1; for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, or 3:1.

[0032] Preferably, the mass ratio of the impregnation solution to the nonwoven base fabric is 1.5~2.5:1.

[0033] Preferably, the first solution is an aqueous solution containing 10-30 wt% DMF; for example, the concentration of DMF in the solution can be 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt%.

[0034] More preferably, the first solution is an aqueous solution containing 15-25 wt% DMF.

[0035] Preferably, the solidification treatment time is 10 to 40 minutes; for example, it can be 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes.

[0036] More preferably, the solidification treatment time is 20-30 minutes.

[0037] Preferably, the second solution is an aqueous solution containing 3 to 15 wt% DMF; for example, the concentration of DMF in the solution can be 3 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, or 15 wt%.

[0038] Preferably, the pre-drying time is 10-30 minutes; for example, it can be 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes.

[0039] Preferably, the water content in the pre-dried base fabric is 0~10wt%; for example, it can be 0wt%, 2wt%, 4wt%, 6wt%, 8wt%, or 10wt%.

[0040] The purpose of pre-drying is to remove most of the water from the base fabric while retaining the DMF in the base fabric.

[0041] Preferably, the gradient drying time is 20-60 min; for example, it can be 20 min, 30 min, 40 min, 50 min, or 60 min.

[0042] More preferably, the gradient drying includes: maintaining at 130~140℃ for 5~15 min, maintaining at 141~150℃ for 5~15 min, and maintaining at 151~160℃ for 10~20 min.

[0043] Gradient drying allows the DMF in the base fabric to evaporate slowly, resulting in a loose and porous internal structure.

[0044] Preferably, the DMF content in the base fabric after gradient drying is 0%.

[0045] A second aspect of the present invention provides an anti-dissolution pore-opening polishing pad, which is obtained by the above-described preparation method.

[0046] Preferably, the mass ratio of nonwoven fabric to polyurethane in the polishing pad is 1~2:3~4; for example, it can be 1:3, 1:4, 2:3, or 2:4.

[0047] Preferably, the air permeability of the polishing pad is 200~700 L / M. 2 / S; for example, it can be 200 L / M 2 / S、300 L / M 2 / S、400 L / M 2 / S、500 L / M 2 / S、600 L / M 2 / S、700 L / M 2 / S.

[0048] More preferably, the air permeability of the polishing pad is 200~300 L / M 2 / S.

[0049] Air permeability refers to the amount of air that can pass through a polishing pad per second or per square meter.

[0050] Preferably, the moisture content of the polishing pad is 100-500 mg / cm³. 3 For example, it could be 100 mg / cm³. 3 200 mg / cm 3 300 mg / cm 3 400 mg / cm 3 500 mg / cm 3 .

[0051] More preferably, the moisture content of the polishing pad is 100-300 mg / cm³. 3 .

[0052] Cultivation capacity refers to the mass of polishing fluid that a polishing pad can absorb and store per cubic centimeter.

[0053] A third aspect of the present invention provides the use of an anti-dissolution aperture polishing pad obtained by the above-described preparation method in the polishing of silicon substrates.

[0054] The fourth aspect of the present invention provides the use of the above-described anti-dissolved aperture polishing pad in the polishing of silicon substrates.

[0055] As described above, the anti-dissolution open-pore polishing pad, its preparation method, and its uses according to the present invention have the following beneficial effects:

[0056] 1. Compared with the traditional non-woven polishing pad manufacturing process, the present invention uses a non-complete water washing process, which allows the polishing pad to retain a certain amount of organic solvent DMF during the drying stage. During the evaporation of DMF, the polyurethane component in the non-woven polishing pad is dissolved to a certain extent. The solvent evaporation process forms channels and increases porosity. After complete evaporation, the polyurethane resin re-solidifies, retaining the hollow part remaining in the polyurethane part during the evaporation of DMF, thereby improving the air permeability and nutrient retention of the polishing pad.

[0057] 2. The polishing pad prepared by the method of the present invention has a loose and porous structure, with high air permeability and moisture retention. During the polishing process, it increases the storage, transportation and chip removal capacity of the polishing fluid, has a good polishing rate, and significantly improves the surface quality of the silicon wafer after polishing.

[0058] 3. This invention uses PET nonwoven fabric as the base fabric, which hardly absorbs water during polishing, and the storage modulus E is not easily fluctuated, resulting in stable polishing efficiency. It uses thermoplastic polyurethane raw materials, and while ensuring good polishing effect, it improves the macroscopic structure of thermoplastic polyurethane to increase the storage and transportation capacity of polishing liquid. Attached Figure Description

[0059] Figure 1 The results show a comparison of polishing rates using polishing pads prepared in Examples 1-5 and Comparative Examples 1-5 of the present invention under the same polishing process.

[0060] Figure 2 The image shown is a cross-sectional microscope view of the polishing pad prepared in Example 1 of this invention.

[0061] Figure 3 The image shown is a cross-sectional microscope view of the polishing pad prepared in Example 5 of this invention.

[0062] Figure 4 The image shown is a cross-sectional microscopic view of the polishing pad prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0063] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0064] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0065] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the presence of other method steps before or after the combined steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0066] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention; in the specification and claims of the present invention, unless otherwise expressly stated in the text, the singular forms "a", "an" and "this" include the plural forms.

[0067] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0068] This invention provides a novel method for preparing a polishing pad, comprising the following steps:

[0069] S1. Add polyurethane resin to DMF to prepare an impregnation solution with a solid content of 10~30wt%.

[0070] S2. The nonwoven base fabric is fully impregnated in the impregnation solution prepared in S1 above.

[0071] S3. Use an aqueous solution containing 10~30wt% DMF to solidify the impregnated base fabric.

[0072] S4. Use an aqueous solution containing DMF to clean the solidified base fabric, ensuring that the DMF content in the solution squeezed out of the base fabric after cleaning is 3~15wt%.

[0073] S5. Pre-dry before drying to reduce the water content in the cleaned base fabric to 0-10%.

[0074] S6. Gradient drying using programmed temperature rise allows DMF to evaporate slowly, forming a hollow, loose structure after evaporation.

[0075] S7. Polish both sides of the sample until there is no obvious resin skin on the surface to obtain a polishing pad.

[0076] The polyurethane resin used in the following embodiments of the present invention is a liquid polyurethane resin with a solid content of 30%, purchased from Asahikawa Chemical. It is a thermoplastic polyurethane resin prepared from polyester polyol and MDI (diphenylmethane diisocyanate), with the product number XCW-6240S. The base fabric used is a PET (polyethylene terephthalate) nonwoven fabric base fabric HLYZ-325NP, purchased from Jiaxing Huali Nonwoven Products Co., Ltd. The fiber length of the base fabric is 55 mm; the fiber fineness is 2.78 dtex; the thickness is 1.8~2.2 mm; and the basis weight is 250~330 g / cm³. 2 .

[0077] Example 1

[0078] This embodiment 1 provides a specific polishing pad and its preparation method, which specifically includes the following steps:

[0079] S1. Weigh 200g of polyurethane resin, add 100g of DMF, and disperse using high-speed stirring for 30 minutes until uniformly dispersed to prepare an impregnation solution with a solid content of 20%.

[0080] S2. Pre-treat the nonwoven base fabric in an oven at 120℃ for 1.5h to remove moisture. Immerse the nonwoven base fabric in the impregnation solution according to the mass ratio of polyurethane resin solids to nonwoven base fabric of 63:37. The immersion time for each immersion is 30min. Use a pressure roller with a gap size of 110% of the thickness of the nonwoven base fabric to squeeze it. Repeat this step 3 times. Then use a rolling mill with a pressure roller gap of 2.0mm to process the base fabric. During the processing, set the temperature to 25℃, the rolling mill pressure to 2.0bar, and the machine speed to 1.5m / min.

[0081] S3. Immerse the nonwoven fabric containing polyurethane resin obtained in step S2 into a 15% DMF aqueous solution for coagulation, ensuring that the nonwoven fabric containing polyurethane resin is completely immersed in the 15% DMF aqueous solution, and the coagulation time is 30 minutes.

[0082] S4. Use a 5% DMF aqueous solution to clean the polyurethane resin-containing nonwoven fabric that has been coagulated in step S3 until the DMF concentration in the nonwoven fabric is measured to be within the range of 5±1% and then stop cleaning.

[0083] S5. Fix the non-woven base fabric that has been cleaned in step S4 onto the needle plate, put it into the drying oven, set the temperature to 80℃ for pre-drying, and dry for 10 minutes. After pre-drying, use a moisture meter to measure the moisture content as 4%.

[0084] S6. Set the oven temperature to gradient heating: 130℃-145℃-155℃, and perform gradient drying for 10min-10min-10min. After completion, take it out and measure the DMF residue, which is 0.

[0085] S7. Polish both sides of the sample until there is no obvious resin skin on the surface to obtain a polishing pad with a thickness of 1.3mm.

[0086] Example 2

[0087] This embodiment 2 provides another specific polishing pad and its preparation method, which differs from embodiment 1 in that:

[0088] In step S3, the nonwoven fabric containing polyurethane resin is immersed in an 18% DMF aqueous solution for coagulation for 30 minutes.

[0089] In step S4, the nonwoven fabric containing polyurethane resin, which has been coagulated in step S3, is cleaned with an aqueous solution of 6% DMF until the DMF concentration in the nonwoven fabric is measured to be within the range of 6±1% and the cleaning is stopped.

[0090] In step S5, the nonwoven base fabric that has been cleaned in step S4 is fixed on the needle plate, placed in an oven, and pre-dried at a temperature of 80°C for 10 minutes. After pre-drying, a moisture meter is used to measure the moisture content as 3%.

[0091] Example 3

[0092] This embodiment 3 provides another specific polishing pad and its preparation method, which differs from embodiment 1 in that:

[0093] In step S3, the nonwoven fabric containing polyurethane resin is immersed in a 20% DMF aqueous solution for coagulation for 30 minutes.

[0094] In step S4, the nonwoven fabric containing polyurethane resin, which has been coagulated in step S3, is cleaned with an aqueous solution of 7% DMF until the DMF concentration in the nonwoven fabric is measured to be within the range of 7±1% and the cleaning is stopped.

[0095] In step S5, the nonwoven base fabric that has been cleaned in step S4 is fixed on the needle plate, placed in an oven, and pre-dried at a temperature of 90°C for 10 minutes. After pre-drying, a moisture meter is used to measure the moisture content as 1%.

[0096] Example 4

[0097] This embodiment 4 provides another specific polishing pad and its preparation method, which differs from embodiment 3 in that:

[0098] In step S3, the nonwoven fabric containing polyurethane resin is immersed in a 22% DMF aqueous solution for coagulation for 30 minutes.

[0099] In step S4, the nonwoven fabric containing polyurethane resin, which has been coagulated in step S3, is cleaned with an 8% DMF aqueous solution until the DMF concentration in the nonwoven fabric is measured to be within the range of 8±1% and the cleaning is stopped.

[0100] Example 5

[0101] This embodiment 5 provides another specific polishing pad and its preparation method, which differs from embodiment 3 in that:

[0102] In step S3, the nonwoven fabric containing polyurethane resin is immersed in a 25% DMF aqueous solution for coagulation for 30 minutes.

[0103] In step S4, the polyurethane resin-containing nonwoven fabric base cloth, which has been coagulated in step S3, is cleaned with an aqueous solution of DMF with a concentration of 9% until the DMF concentration in the liquid extrusion test of the nonwoven fabric base cloth is within the range of 9±1%, at which point the cleaning is stopped.

[0104] Comparative Example 1

[0105] Comparative Example 1 is a comparative example of Example 3, and its difference from Example 3 is as follows:

[0106] In step S4, the nonwoven fabric containing polyurethane resin, which has been coagulated in step S3, is cleaned with an aqueous solution of 0% DMF until the liquid in the nonwoven fabric is squeezed out and the DMF concentration is measured to be 0, at which point the cleaning is stopped.

[0107] In step S5, the nonwoven base fabric that has been cleaned in step S4 is fixed on the needle plate, placed in an oven, and pre-dried at a temperature of 80°C for 10 minutes. After pre-drying, a moisture meter is used to measure the moisture content as 5%.

[0108] Comparative Example 2

[0109] Comparative Example 2 is a comparative example of Examples 1-5, and its difference from Examples 1-5 is as follows:

[0110] In step S3, the nonwoven fabric containing polyurethane resin is immersed in a 30% DMF aqueous solution for coagulation for 30 minutes.

[0111] In step S4, the polyurethane resin-containing nonwoven fabric base that has been coagulated in step S3 is cleaned with an aqueous solution of 17% DMF until the DMF concentration in the liquid extrusion test of the nonwoven fabric base is within the range of 17±1%, at which point the cleaning is stopped.

[0112] In step S5, the nonwoven base fabric that has been cleaned in step S4 is fixed on the needle plate, placed in an oven, and pre-dried at a temperature of 80°C for 10 minutes. After pre-drying, a moisture meter is used to measure the moisture content as 5%.

[0113] Comparative Example 3

[0114] Comparative Example 3 is a comparative example of Example 1, and its difference from Example 1 is as follows:

[0115] In step S5, the nonwoven base fabric that has been cleaned in step S4 is fixed on the needle plate, placed in an oven, and pre-dried at a temperature of 70°C for 7 minutes. After pre-drying, a moisture meter is used to measure the moisture content, which is 14%.

[0116] Comparative Example 4

[0117] Comparative Example 4 is a comparative example of Example 1, and its difference from Example 1 is as follows:

[0118] The pre-drying treatment in step S5 is omitted. After cleaning the polyurethane resin-containing nonwoven fabric base that has been solidified in step S3 with a 5% DMF aqueous solution, the gradient heating in step S6 is carried out directly to dry the water and DMF together.

[0119] Comparative Example 5

[0120] Comparative Example 5 is a comparative example of Example 1, and its difference from Example 1 is as follows:

[0121] In step S3, the nonwoven fabric containing polyurethane resin is immersed in a 0% DMF aqueous solution for coagulation for 20 minutes.

[0122] In step S4, the nonwoven fabric containing polyurethane resin, which has been coagulated in step S3, is cleaned using an aqueous solution of 0% DMF.

[0123] The key parameter settings in the preparation methods of Examples 1-5 and Comparative Examples 1-5 are shown in Table 1 below.

[0124] Table 1. Key parameter settings in the preparation methods of Examples 1-5 and Comparative Examples 1-5

[0125]

[0126] Test section

[0127] The polishing pads prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to hardness testing, density testing, air permeability testing, moisture retention testing, scratch detection, and Ra value detection. The test results are shown in Table 2. The specific test methods are as follows:

[0128] 1) Hardness test: The test shall be conducted according to the method in GB / T 2411-2008;

[0129] 2) Density test: The apparent core density was determined using the method in GB / T 6343-2009. The size of the sample to be tested was 300mm×300mm×3.0mm.

[0130] 3) Air permeability test: Fabric air permeability tester, model G571, set parameters: test area 38cm² 2 The test pressure was 1000 Pa.

[0131] 4) Static water absorption test: The static water absorption was determined using the method in GB / T 4689.21-2008. The sample size was 100 cm². 2 .

[0132] 5) Polishing process: 36-inch NTS polishing machine; polishing object: 4-inch silicon wafer; polishing fluid: SIPOL-1801; polishing pressure: 300g / cm 3 Lower plate rotation speed: 40 rpm; Polishing time: 60 min / run; Flow rate: 2.28 L / min.

[0133] 6) Scratch detection: Scratch detection is performed on the polished wafer. Under a strong light (Yamada Optical YP250), the wafer is observed with the naked eye. Bright lines with a length of more than 2cm are judged as scratches, and the number of scratches is recorded.

[0134] 7) Surface roughness test: Randomly select 3 points with a size of 5μm on the polished wafer and use atomic force microscopy (AFM) to test the Ra value, and take the average value of the 3 points.

[0135] Table 2 Test Results

[0136]

[0137] As can be seen from the results in Table 2, the air permeability of the polishing pads prepared in Examples 1-5 is all >200 L / M. 2 / S, nutrient capacity is greater than 150 mg / cm² 3No scratches were found on the surface of the polished wafers, and the Ra values ​​were all <0.16 nm. In the drying stage of the polishing pads in Examples 1-5, a small amount of DMF was retained in the nonwoven fabric base during the preparation process. During the gradient heating drying process, the DMF slowly evaporated, and in the process of evaporation, it dissolved a certain amount of polyurethane resin in the polishing pad. After complete evaporation, the polyurethane resin re-solidified, retaining the hollow structure remaining in the polyurethane part during the evaporation of DMF. The polishing pads prepared in this way have suitable air permeability and moisture retention, ensuring the surface quality of the silicon wafers after polishing.

[0138] In Comparative Example 1, the nonwoven fabric base was cleaned with DMF-free water, resulting in a DMF-free base. Consequently, the nonwoven fabric base could not form a loose, porous structure during the subsequent drying process, leading to decreased air permeability and moisture retention. The resulting polishing pad was too dense and hard, easily scratching the silicon wafer during polishing and causing surface unevenness defects, resulting in a decrease in the surface roughness Ra of the wafer after polishing. In Comparative Example 2, the excessive DMF residue in the nonwoven fabric base before drying resulted in an overly soft, loose, and porous structure during the subsequent drying process, significantly increasing air permeability and moisture retention. The soft and loose structure of the polishing pad caused deformation under polishing pressure, resulting in severe butterfly pits and wafer surface erosion. Erosion leads to a decrease in the surface quality of the wafer after polishing; in Comparative Example 3, the moisture content after pre-drying is too high, which will affect the dissolution effect of DMF on polyurethane during the subsequent gradient heating process, which is not conducive to the formation of a loose and porous structure, and reduces the air permeability and nutrient content. During the polishing process, the wafer is easily damaged, resulting in an increase in surface roughness; in Comparative Example 4, no pre-drying treatment is performed, and a large amount of water remains during the subsequent gradient heating process. The polishing pad is still relatively dense and hard, which can easily damage the wafer during the polishing process, resulting in an increase in surface roughness; in Comparative Example 5, the non-woven fabric base does not contain DMF during the solidification and drying process. As a result, the final polishing pad structure is dense and hard, which can easily damage the wafer during the polishing process.

[0139] Polishing was performed using the polishing process described above and the polishing pads prepared in each embodiment and comparative example. The mass before and after polishing was measured using a 1 / 2 ppm balance, denoted as M. The calculation formula is as follows: RR = M / (S*ρ) / t. The polishing rate obtained by the calculation is as follows: Figure 1 As shown.

[0140] according to Figure 1The results show that: when polishing silicon wafers using the polishing pads prepared in Examples 1-5, the polishing rate can be stably maintained at 700-850 nm / min within 79 hours, allowing for stable and continuous polishing. However, when polishing silicon wafers using the polishing pads prepared in Comparative Examples 1 and 3-5, the polishing rate shows two significant decreases around 30 and 60 hours, with the polishing rate falling below 700 nm / min after 60 hours. This is because the polishing pads have insufficient moisture content and permeability, preventing the polishing slurry from effectively remaining at the polishing interface, resulting in insufficient chemical reaction. The debris generated after polishing cannot be removed in time and accumulates at the polishing interface, hindering polishing and thus reducing the polishing rate. When polishing silicon wafers using the polishing pad prepared in Comparative Example 2, severe wear of the polishing pad causes machine vibration, making it impossible to meet polishing conditions after approximately 35 hours. This is due to its overly loose and porous structure. Too many pores will absorb the polishing fluid, reducing the amount of polishing fluid at the polishing interface, resulting in a lower polishing rate. Furthermore, under long-term pressure and friction, it wears out faster, deforms more severely, and has a shorter service life.

[0141] To further examine the internal morphology of the polishing pads, polishing pads prepared in Examples 1, 5, and Comparative Example 1 were subjected to cross-sectional microscopy observation. The observation results are as follows: Figures 2-4 As shown, Figure 2 and Figure 3 As shown, the polishing pads prepared in Examples 1 and 5 have a loose and delicate internal skeleton structure. The polyurethane resins are interwoven to form a sponge-like fluffy structure with large and uneven pores. The pores are interconnected, forming a continuous multi-layered network structure. In contrast, the polishing pad prepared in Comparative Example 1 is shaped like a dense, rigid foam with small and uniform pores, approximately closed spherical pores, poor connectivity, and a dense, continuous, and thick overall skeleton.

[0142] In summary, this invention provides a novel method for preparing a polishing pad. The polishing pad obtained by this method has suitable density, hardness, air permeability, and moisture content. It exhibits excellent and stable polishing rate during a continuous polishing process of up to 79 hours and can significantly improve the surface quality of the polished silicon wafer, thus possessing great industrial application value.

[0143] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing an anti-dissolved porous polishing pad, characterized in that, The preparation method includes: immersing a nonwoven base fabric in an impregnation solution containing polyurethane resin to obtain a polyurethane resin-containing base fabric; immersing the polyurethane resin-containing base fabric in a first solution for coagulation treatment; cleaning the coagulated base fabric with a second solution; and sequentially pre-drying, gradient drying, and polishing the cleaned base fabric to obtain a polishing pad; wherein the first and second solutions are aqueous solutions containing DMF, the concentration of DMF in the liquid extruded from the cleaned base fabric is 3-15 wt%, the pre-drying temperature is 80-100℃, and the gradient drying temperature is 130-180℃; the first solution is an aqueous solution containing 10-30 wt% DMF; the coagulation treatment time is 10-40 min; and the second solution is an aqueous solution containing 3-15 wt% DMF.

2. The preparation method according to claim 1, characterized in that, The solid content of polyurethane resin in the impregnation solution is 10~30wt%; And / or, the solvent of the impregnation solution is DMF; The polyurethane resin is a thermoplastic polyurethane resin; And / or, the molecular weight of the polyurethane resin is 10,000 to 70,000 Da; And / or, the modulus of the polyurethane resin is 8~30 MPa; The polyurethane resin molecular chain is composed of hard segments and soft segments. The hard segments are formed by the reaction of diisocyanate and chain extender, and the soft segments are composed of polyols. The diisocyanate is selected from any one or more of diphenylmethane diisocyanate, toluene diisocyanate, terephthalic diisocyanate, and naphthalene-1,5-diisocyanate. The chain extender is selected from any one or more of 1,4-butanediol, ethylene glycol, hydroquinone-bis(2-hydroxyethyl) ether, and hydroquinone dihydroxyethyl ether. The polyol is selected from any one or more of polybutanediol, polypropylene oxide, polyethylene oxide, polyadipate polyol, polycaprolactone, and polycarbonate polyol.

3. The preparation method according to claim 1, characterized in that, The nonwoven fabric is a polyester fiber nonwoven fabric made by needle punching or hydroentanglement process; And / or, the fiber fineness of the nonwoven fabric is 2~10 dtex; And / or, the fiber length of the nonwoven fabric is 30~80mm; And / or, the thickness of the nonwoven fabric is 1.8~2.2mm; And / or, the basis weight of the nonwoven fabric is 250~330 g / m². 2 .

4. The preparation method according to claim 1, characterized in that, The preparation method also includes squeezing the base fabric after soaking to remove excess impregnation liquid; And / or, the mass ratio of polyurethane resin solids to nonwoven fabric base fabric in the impregnation solution is 1~3:

1.

5. The preparation method according to claim 1, characterized in that, The pre-drying time is 10~30 minutes; And / or, the water content in the pre-dried base fabric is 0~10wt%.

6. The preparation method according to claim 1, characterized in that, The gradient drying time is 20~60 min; And / or, the DMF content in the base fabric after gradient drying is 0 wt%.

7. A reverse-solution open-pore polishing pad, characterized in that, The polishing pad is obtained by the preparation method described in any one of claims 1 to 6.

8. The polishing pad according to claim 7, characterized in that, The mass ratio of nonwoven fabric to polyurethane resin in the polishing pad is 1~2:3~4; And / or, the air permeability of the polishing pad is 200~700 L / M 2 / S; And / or, the moisture content of the polishing pad is 100-500 mg / cm³. 3 .

9. The use of an anti-dissolved aperture polishing pad obtained by the preparation method according to any one of claims 1 to 6, and / or the use of the anti-dissolved aperture polishing pad according to any one of claims 7 to 8 in the polishing of silicon substrates.

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