A preparation method of a chemical mechanical polishing pad buffer layer, a buffer layer, a polishing pad containing the same and applications

Abstract

The application provides a preparation method of a chemical mechanical polishing pad buffer layer, comprising the following steps: a) dissolving polyurethane resin and additives in a solvent to prepare a slurry; b) uniformly coating the slurry on non-woven fabric with a certain thickness, and step-by-step solidification forming in a first coagulation bath and a second coagulation bath; and c) separating the non-woven fabric and washing and drying to obtain the buffer layer. The application also provides the buffer layer and application of a polishing pad containing the same in chemical mechanical polishing, which can improve the surface flatness of the polishing pad during polishing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical mechanical polishing, in particular to a preparation method of a chemical mechanical polishing pad buffer layer, a buffer layer, a polishing pad containing the same and application. BACKGROUND

[0002] Chemical mechanical polishing (CMP) is a process that combines the action of nanoscale particles and the chemical corrosion of polishing liquid to make the workpiece being polished on the polishing pad to be planarized. Chemical mechanical polishing has been widely used in the planarization process of semiconductor wafers and is an essential processing process in the production of wafers for manufacturing electronic components.

[0003] As a key consumable in the chemical mechanical polishing process, the composition and structure of the polishing pad play a crucial role in the processing quality of the polished material surface. The overall structure of the polishing pad is generally divided into three parts, from top to bottom, the polishing layer, the buffer layer and the backing layer (release layer). Soft polyurethane microporous polishing pads are usually used for finishing or final polishing to achieve a low defect rate of the polished material.

[0004] For soft polyurethane microporous polishing pads, most of the current methods for improving the flatness of the polished material are to adjust the structure of the polishing layer, and most of them use hard PET as the buffer layer material. For example, patent CN102574267A provides a retaining pad that improves the flatness accuracy of the retaining surface and enhances the in-plane uniformity of the polished material. The polishing layer structure can be divided into several parts in the vertical height direction, and the porosity of each part is controlled to maintain the flatness accuracy of the retaining surface and enhance the in-plane uniformity of the polished material during polishing. In fact, it is difficult to control the change of the pore size in the vertical direction when preparing the polishing layer. Patent US6899602B2 provides a method of sanding the surface of the polishing layer to increase the number of pores on the surface of the polishing layer and reduce the roughness of the surface of the polishing layer to improve the flatness of the polished material. This method will affect the pore size of the polishing layer surface and will affect the polishing rate. SUMMARY

[0005] The buffer layer material is a key material in the microporous polyurethane polishing pad, which has important functions such as buffering pressure and reducing edge effect. The applicant has made further attempts and optimizations in the preparation method of the buffer layer material in an attempt to solve the problems existing in the prior art and improve the performance of the polishing pad, thereby completing the present application.

[0006] To overcome the shortcomings of existing technologies, this invention provides a buffer layer for chemical mechanical polishing pads. The buffer layer prepared by the method of this invention can provide better elastic recovery for the polishing pad, improve the stress uniformity in the middle and edges of the polishing material, increase the contact area between the polishing material and the polishing pad, and improve the flatness of the polishing material surface.

[0007] Another object of the present invention is to provide a chemical mechanical polishing pad buffer layer prepared by this method.

[0008] Another object of the present invention is to provide a polishing pad made from such a buffer layer and its application in chemical mechanical polishing.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0010] A method for preparing a buffer layer for a chemical mechanical polishing pad includes the following steps:

[0011] a) Dissolve polyurethane resin and additives in a solvent to prepare a slurry; preferably, the solvent is selected from any one of N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone, more preferably N,N-dimethylformamide;

[0012] b) The slurry is evenly coated on the nonwoven fabric with a certain thickness and then solidified step by step in the first coagulation bath and the second coagulation bath;

[0013] c) The nonwoven fabric is separated, washed, and dried to obtain a buffer layer.

[0014] In one specific embodiment, the polyurethane resin in step a) is a solvent-based polyurethane resin, preferably a wet-process polyurethane resin, more preferably a wet-process polyurethane resin for leather; preferably, the 100% modulus of the solvent-based polyurethane resin is 3-10 MPa, more preferably 5-8 MPa.

[0015] In one specific embodiment, the additive in step a) is a nonionic surfactant, preferably selected from one or more of polyoxyethylene sorbitan monooleate (Tween-80), polyoxyethylene sorbitan palmitate monooleate (Tween-40), polyethylene glycol (400) monooleate and polyethylene glycol (400) monostearate; more preferably, the mass ratio of the polyurethane resin, additive and solvent is 100:2 to 4:40 to 45.

[0016] In one specific embodiment, the slurry coating thickness in step b) is 0.30–0.48 mm, preferably 0.36–0.40 mm; preferably, the air permeability of the nonwoven fabric in step b) is 1.50–2.00 cc / cm². 2 / sec, preferably 1.60~1.90cc / cm 2 / sec.

[0017] In one specific embodiment, the first coagulation bath and the second coagulation bath in step b) are mixtures of N,N-dimethylformamide and water; preferably, the mass ratio of N,N-dimethylformamide in the first coagulation bath is 5% to 10%, more preferably 6% to 8%; and the mass ratio of N,N-dimethylformamide in the second coagulation bath is 20% to 40%, more preferably 25% to 30%.

[0018] In one specific embodiment, in step b), the curing time in the first coagulation bath is 10-15 min, preferably 12-14 min, and the curing time in the second coagulation bath is 20-40 min, preferably 30-35 min.

[0019] In one specific embodiment, the drying temperature in step c) is 80-150°C, preferably 100-120°C; the drying time is 10-50 min, preferably 20-40 min.

[0020] On the other hand, a chemical mechanical polishing pad buffer layer prepared by the aforementioned preparation method is divided into a sponge layer located at the top, a sponge layer with uniformly distributed large pores located in the middle, and a sponge layer located at the bottom in the vertical direction.

[0021] On the other hand, a chemical mechanical polishing pad is made of a polishing layer, a buffer layer prepared by the aforementioned method, and a release layer bonded together.

[0022] On the other hand, the aforementioned chemical mechanical polishing pads are used in chemical mechanical polishing.

[0023] Compared with existing technologies, the chemical mechanical polishing pad buffer layer prepared by the method of the present invention has the following beneficial effects:

[0024] 1) The preparation process of the buffer layer of the present invention is relatively simple. It is prepared by coating polyurethane on non-woven fabric using a non-solvent phase inversion method, and the non-woven fabric material can be reused.

[0025] 2) The buffer layer prepared by the present invention can provide better elastic recovery for the polishing pad, improve the stress uniformity in the middle and edge of the polishing material, increase the contact area between the polishing material and the polishing pad, and improve the flatness of the polishing material surface. Attached Figure Description

[0026] Figure 1 The image shows the scanning electron microscope (SEM) image of the chemical mechanical polishing pad buffer layer prepared in Example 1 of this invention.

[0027] Figure 2The image shows the scanning electron microscope (SEM) image of the chemical mechanical polishing pad buffer layer prepared in Comparative Example 1 of this invention.

[0028] Among them, 1 is the upper sponge layer, 2 is the middle sponge layer with uniformly distributed large pores, and 3 is the lower sponge layer. Detailed Implementation

[0029] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0030] A method for preparing a buffer layer for a chemical mechanical polishing pad, the method comprising the following steps:

[0031] a) Dissolve polyurethane resin and additives in N,N-dimethylformamide to prepare a slurry;

[0032] b) The slurry is evenly coated onto the nonwoven fabric at a certain thickness and then cured in a coagulation bath.

[0033] c) The nonwoven fabric is separated, washed, and dried to obtain a buffer layer.

[0034] In step a), N,N-dimethylformamide is used only as a solvent. Those skilled in the art will understand that, in addition to N,N-dimethylformamide, the solvent may also be any one of N,N-dimethylacetamide or N-methylpyrrolidone; N,N-dimethylformamide is more preferred.

[0035] In step a), the polyurethane resin is selected from solvent-based polyurethane resins, preferably wet-process polyurethane resins, and more preferably wet-process polyurethane resins for leather. The solid content of the wet-process polyurethane resin is not particularly limited; for example, it is generally 30%. There are no restrictions on the manufacturer; for example, it could be Shanghai Huide Technology HDW-1151EB, etc., but it is not limited to these. Preferably, the solvent-based polyurethane resin used in this invention has a 100% modulus of 3–10 MPa, including but not limited to 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, and 10 MPa, preferably 5–8 MPa. Here, 100% modulus can also be referred to as 100% mold or 100% modulus, and both have the same meaning in this invention.

[0036] The additive is selected from nonionic surfactants, preferably from one or a mixture of polyoxyethylene sorbitan monooleate (Tween-80), polyoxyethylene sorbitan palmitate monooleate (Tween-40), polyethylene glycol (400) monooleate and polyethylene glycol (400) monostearate.

[0037] The mass ratio of the polyurethane resin, additives, and solvent N,N-dimethylformamide is 100:2 to 4:40 to 45, for example, including but not limited to 100:2:40, 100:3:42, 100:4:45, etc.

[0038] In step b), the uniform coating can be achieved using existing technology, and this invention has no limitations. For example, a coating machine or a scraper can be used for coating. The key to this invention is to control the coating thickness to be 0.30 to 0.48 mm, such as including but not limited to 0.30 mm, 0.32 mm, 0.34 mm, 0.36 mm, 0.38 mm, 0.40 mm, 0.42 mm, 0.44 mm, 0.46 mm, and 0.48 mm, preferably 0.36 to 0.40 mm.

[0039] The nonwoven fabric can be made of any material, such as polyester or multi-layered fiber composite, and its air permeability is preferably 1.50 to 2.00 cc / cm. 2 / sec, for example, including but not limited to 1.50cc / cm 2 / sec, 1.55cc / cm 2 / sec, 1.60cc / cm 2 / sec, 1.65cc / cm 2 / sec, 1.70cc / cm 2 / sec, 1.75cc / cm 2 / sec, 1.80cc / cm 2 / sec, 1.85cc / cm 2 / sec, 1.90cc / cm 2 / sec, 1.95cc / cm 2 / sec, 2.00cc / cm 2 / sec, preferably 1.60~1.90cc / cm 2 / sec.

[0040] The coagulation bath is divided into a first coagulation bath and a second coagulation bath. The coagulation bath is a mixture of N,N-dimethylformamide and water. The mass ratio of N,N-dimethylformamide in the first coagulation bath is 5% to 10%, for example, 5%, 6%, 7%, 8%, 9%, 10%, but not limited thereto, preferably 6% to 8%. The mass ratio of N,N-dimethylformamide in the second coagulation bath is 20% to 40%, for example, 20%, 25%, 30%, 35%, 40%, but not limited thereto, preferably 25% to 30%.

[0041] The curing time in the first coagulation bath is 10 to 15 minutes, for example, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, or 15 minutes, but is not limited thereto, and is preferably 12 to 14 minutes. The curing time in the second coagulation bath is 20 to 40 minutes, for example, 20 minutes, 30 minutes, or 40 minutes, but is not limited thereto, and is preferably 30 to 35 minutes.

[0042] In this invention, there are no particular limitations on the temperature in the first coagulation bath and the second coagulation bath. The temperature can be the curing temperature commonly used in the art, such as 10 to 40°C, and it can usually be carried out at room temperature.

[0043] In step c), the drying temperature is 80 to 150°C, for example, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, but not limited thereto, and preferably 100 to 120°C.

[0044] The drying time is 10 to 50 minutes, for example, 10 minutes, 20 minutes, 30 minutes, 40 minutes, or 50 minutes, but is not limited thereto, and is preferably 20 to 40 minutes.

[0045] The buffer layer prepared by the above method is divided into three parts in the vertical direction. Each part accounts for about 1 / 3 of the total thickness of the buffer layer. The uppermost and lowermost parts are sponge layers, and the middle part is a sponge layer with large pores evenly distributed.

[0046] By combining a polishing layer with a buffer layer prepared by the above method using existing technology, then attaching an adhesive backing and a release layer, a microporous polyurethane polishing pad is obtained. This microporous polyurethane polishing pad can be applied to the field of chemical mechanical polishing, including but not limited to the chemical mechanical polishing of silicon wafers, sapphire, etc.

[0047] The present invention will be further explained and illustrated below through more specific embodiments, but these do not constitute any limitation.

[0048] The main sources of raw materials used in the embodiments and comparative examples of this invention are shown in Table 1:

[0049] Table 1. Sources of main raw materials for examples and comparative examples

[0050]

[0051]

[0052] Unless otherwise specified, all other raw materials or reagents are obtained through commercial channels.

[0053] Buffer layer evaluation parameters:

[0054] ① Buffer layer thickness: The microstructure of the buffer layer cross section was observed using a VEGA TS5136XM scanning electron microscope, and the thickness of the buffer layer was measured using the scale of the scanning electron microscope's built-in software.

[0055] ② Buffer layer hardness: The Shore A hardness (test standard JIS K 6253) is used to determine the depth that can be measured by pressing the indenter against the surface of the test piece with a spring.

[0056] ③ Buffer layer compressibility: According to the test standard JIS L 1021, using a SCHOPPER type thickness measuring instrument, with a pressure surface of 1cm, the compressibility is measured using an initial load of 100g / cm. 2 The thickness t0 after applying pressure for 30 seconds was then measured at the final pressure of 1120 g / cm³. 2 After applying pressure for 5 minutes, the thickness t1, excluding the total load, has a compression rate (%) of 100 × (t0 - t1) / t1.

[0057] ④ Polishing test: Polishing test was conducted using an E460 CMP testing machine, ANJI AEP U3061A polishing fluid, polishing pad diameter 609mm, and copper target diameter 75mm.

[0058] The polishing parameters are as follows: polishing pressure 1.5psi, polishing speed 50-60rpm, polishing fluid flow rate 300mL / min, and polishing time 60s.

[0059] The film thickness was measured using an AMBioS XP-300 profilometer, and the average value of nine points was taken. The copper target removal rate was determined based on the difference before and after CMP. and non-uniformity % (NU%).

[0060] Example 1

[0061] Preparation of polishing layer: 100 parts of polyurethane resin (Huada Chemical, trade name AH-1502F), 40 parts of carbon black paste, 2 parts of Span-80, and 40 parts of N,N-dimethylformamide were formulated into a polyurethane slurry. The slurry was uniformly coated on the support layer with a thickness of 1.7 mm, immersed in room temperature water to cure and form. After drying, the surface was sanded and embossed with grooves using 220-grit sandpaper to obtain the polishing layer with a thickness of 0.70 mm.

[0062] Preparation of the buffer layer: 100 parts of solvent-based polyurethane resin ②, 2 parts of Tween-80, and 45 parts of N,N-dimethylformamide were mixed to prepare a polyurethane slurry. The slurry was coated onto nonwoven fabric ② with a thickness of 0.36 mm. The nonwoven fabric was then immersed in a first coagulation bath containing 8% N,N-dimethylformamide and cured for 12 min. Then, it was immersed in a second coagulation bath containing 25% N,N-dimethylformamide and cured for 30 min. After separating the nonwoven fabric, the buffer layer was placed in an oven at 100℃ and dried for 20 min.

[0063] After the above drying steps, a buffer layer is obtained. The polishing layer and the buffer layer are combined using existing steps, and then an adhesive backing is applied. Finally, a release layer is applied to obtain a microporous polyurethane polishing pad.

[0064] The scanning electron microscope (SEM) image of the prepared buffer layer is shown below. Figure 1 As shown, the buffer layer is divided into three parts in the vertical direction, each part accounting for 1 / 3 of the overall thickness of the buffer layer. The uppermost and lowermost parts are sponge layers 1 and 3, and the middle part is sponge layer 2 with large pores evenly distributed.

[0065] Example 2

[0066] The polishing layer is the same as that used in Example 1.

[0067] Preparation of the buffer layer: 100 parts of solvent-based polyurethane resin ③, 2 parts of Tween-40, and 45 parts of N,N-dimethylformamide were mixed to prepare a polyurethane slurry. The slurry was coated on nonwoven fabric ③ with a thickness of 0.40 mm and then immersed in a first coagulation bath containing 6% N,N-dimethylformamide for 14 min. Then, it was immersed in a second coagulation bath containing 30% N,N-dimethylformamide for 35 min. After separating the nonwoven fabric, the buffer layer was placed in an oven at 120℃ and dried for 40 min.

[0068] After the above drying steps, a buffer layer is obtained. The polishing layer and the buffer layer are combined using existing steps, and then an adhesive backing is applied. Finally, a release layer is applied to obtain a microporous polyurethane polishing pad.

[0069] Example 3

[0070] The polishing layer is the same as that used in Example 1.

[0071] Preparation of the buffer layer: 100 parts of solvent-based polyurethane resin ①, 2 parts of polyethylene glycol (400) monooleate, and 45 parts of N,N-dimethylformamide were mixed to prepare a polyurethane slurry. The slurry was coated on nonwoven fabric ④ with a thickness of 0.30 mm and then immersed in a first coagulation bath containing 5% N,N-dimethylformamide for 10 min. Then, it was immersed in a second coagulation bath containing 40% N,N-dimethylformamide for 20 min. After separating the nonwoven fabric, the buffer layer was placed in an 80℃ oven and dried for 10 min.

[0072] After the above drying steps, a buffer layer is obtained. The polishing layer and the buffer layer are combined using existing steps, and then an adhesive backing is applied. Finally, a release layer is applied to obtain a microporous polyurethane polishing pad.

[0073] Example 4

[0074] The polishing layer is the same as that used in Example 1.

[0075] Preparation of the buffer layer: 100 parts of solvent-based polyurethane resin ④, 2 parts of polyethylene glycol (400) monostearate, and 45 parts of N,N-dimethylformamide were mixed to prepare a polyurethane slurry. The slurry was coated on nonwoven fabric ① with a thickness of 0.48 mm and then immersed in a first coagulation bath containing 10% N,N-dimethylformamide for 15 min. Then, it was immersed in a second coagulation bath containing 20% ​​N,N-dimethylformamide for 40 min. After separating the nonwoven fabric, the buffer layer was placed in an oven at 150℃ and dried for 50 min.

[0076] After the above drying steps, a buffer layer is obtained. The polishing layer and the buffer layer are combined using existing steps, and then an adhesive backing is applied. Finally, a release layer is applied to obtain a microporous polyurethane polishing pad.

[0077] Comparative Example 1

[0078] The polishing layer is the same as that used in Example 1.

[0079] The buffer layer was prepared using the same steps as in Example 1, except that the slurry was coated onto the nonwoven fabric ⑤.

[0080] After the above drying steps, a buffer layer is obtained. The polishing layer and the buffer layer are combined using existing steps, and then an adhesive backing is applied. Finally, a release layer is applied to obtain a microporous polyurethane polishing pad.

[0081] The scanning electron microscope (SEM) image of the prepared buffer layer is shown below. Figure 2 As shown, the buffer layer has a relatively small number of large pores and they are unevenly distributed.

[0082] Comparative Example 2

[0083] The polishing layer is the same as that used in Example 1.

[0084] The buffer layer was prepared using the same steps as in Example 2, except that the second coagulation bath contained 45% N,N-dimethylformamide.

[0085] After the above drying steps, a buffer layer is obtained. The polishing layer and the buffer layer are combined using existing steps, and then an adhesive backing is applied. Finally, a release layer is applied to obtain a microporous polyurethane polishing pad.

[0086] Comparative Example 3

[0087] The polishing layer is the same as that used in Example 1.

[0088] The buffer layer was prepared using the same steps as in Example 3, except that the thickness of the slurry coating on the nonwoven fabric was 0.50 mm.

[0089] After the above drying steps, a buffer layer is obtained. The polishing layer and the buffer layer are combined using existing steps, and then an adhesive backing is applied. Finally, a release layer is applied to obtain a microporous polyurethane polishing pad.

[0090] Comparative Example 4

[0091] The polishing layer is the same as that used in Example 1.

[0092] The buffer layer was prepared using the same steps as in Example 4, except that 100 parts of solvent-based polyurethane resin ⑤ were used.

[0093] After the above drying steps, a buffer layer is obtained. The polishing layer and the buffer layer are combined using existing steps, and then an adhesive backing is applied. Finally, a release layer is applied to obtain a microporous polyurethane polishing pad.

[0094] Comparative Example 5

[0095] The polishing layer is the same as that used in Example 1.

[0096] Using commercially available PET film (JP-TPET188) as a buffer layer, the polishing layer and the buffer layer are combined using existing steps, then adhesive is applied, and a release layer is attached to obtain a microporous polyurethane polishing pad.

[0097] Comparative Example 6

[0098] The polishing layer is the same as that used in Example 1.

[0099] The buffer layer was prepared using the same steps as in Example 1, except that the concentration of N,N-dimethylformamide in the first coagulation bath was 2%.

[0100] After the above drying steps, a buffer layer is obtained. The polishing layer and the buffer layer are combined using existing steps, and then an adhesive backing is applied. Finally, a release layer is applied to obtain a microporous polyurethane polishing pad.

[0101] Comparative Example 7

[0102] The polishing layer is the same as that used in Example 1.

[0103] The buffer layer was prepared using the same steps as in Example 1, except that the curing time in the second coagulation bath was 15 minutes.

[0104] After the above drying steps, a buffer layer is obtained. The polishing layer and the buffer layer are combined using existing steps, and then an adhesive backing is applied. Finally, a release layer is applied to obtain a microporous polyurethane polishing pad.

[0105] The test results of the thickness, hardness, and compressibility of the buffer layer prepared in the examples and comparative examples are shown in Table 2.

[0106] Table 2. Test results of buffer layer thickness, hardness, and compressibility.

[0107]

[0108]

[0109] The removal rate and non-uniformity of the polishing pads prepared in the examples and comparative examples were obtained by polishing tests. The test results are shown in Table 3.

[0110] Table 3. Results of Removal Rate and Non-uniformity Tests

[0111]

[0112] As can be seen from the test results in Table 3, the polishing pad prepared by the buffer layer of the present invention can improve the flatness of the polishing material surface.

[0113] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing a chemical mechanical polishing pad cushion layer, characterized by, The method comprises the following steps: a) dissolving polyurethane resin, additives in solvent to prepare slurry; the polyurethane resin is solvent type polyurethane resin, and the 100% modulus of the solvent type polyurethane resin is 3-10 MPa; b) uniformly coating the slurry on non-woven fabric with a thickness of 0.30-0.48 mm and forming by step curing in a first coagulation bath and a second coagulation bath; c) separating the non-woven fabric and washing and drying to obtain a buffer layer; The non-woven fabric has a air permeability of 1.50-2.00 cc / cm 2 / sec; the first coagulation bath and the second coagulation bath are a mixture of N,N-dimethylformamide and water; the mass ratio of N,N-dimethylformamide in the first coagulation bath is 5%-10%, and the mass ratio of N,N-dimethylformamide in the second coagulation bath is 20%-40%; the solidification forming time in the first coagulation bath is 10-15 min, and the solidification forming time in the second coagulation bath is 20-40 min.

2. The production method according to claim 1, characterized by, the solvent in the step a) is any one of N, N-dimethylformamide, N, N-dimethylacetamide or N-methylpyrrolidone.

3. The production method according to claim 2, characterized by, the solvent in the step a) is N, N-dimethylformamide.

4. The method of claim 1, wherein, the polyurethane resin in the step a) is wet polyurethane resin.

5. The preparation method according to claim 4, characterized in that, the polyurethane resin is wet polyurethane resin for leather.

6. The method of claim 1, wherein, the 100% modulus of the solvent type polyurethane resin is 5-8 MPa.

7. The method of any one of claims 1-6, wherein, the additive in the step a) is non-ionic surfactant.

8. The preparation method according to claim 7, characterized in that, the additive is one or more of polyoxyethylene sorbitan monooleate (Tween-80), polyoxyethylene sorbitan palmitate (Tween-40), polyethylene glycol (400) monooleate and polyethylene glycol (400) monostearate.

9. The preparation method according to claim 7, characterized in that, the mass ratio of the polyurethane resin, additive and solvent is 100:2-4:40-45.

10. The method of claim 1, wherein, the coating thickness of the slurry in the step b) is 0.36-0.40 mm.

11. The method of claim 10, wherein, The air permeability of the nonwoven fabric in step b) is 1.60 to 1.90 cc / cm 2 / sec.

12. The method of claim 1, wherein, the mass ratio of N, N-dimethylformamide in the first coagulation bath is 6%-8%; the mass ratio of N, N-dimethylformamide in the second coagulation bath is 25%-30%.

13. The production method according to claim 1 or 12, characterized by, the forming time in the first coagulation bath in the step b) is 12-14 min, and the forming time in the second coagulation bath is 30-35 min.

14. The method of claim 1, wherein, the drying temperature in the step c) is 80-150 ℃; and the drying time is 10-50 min.

15. The preparation method according to claim 14, characterized in that, the drying temperature in the step c) is 100-120 ℃; and the drying time is 20-40 min.

16. The cushioning layer for a chemical mechanical polishing pad prepared by the method of any one of claims 1 to 15, characterized in that, the buffer layer is divided into a sponge layer at the upper part, a sponge layer with uniformly distributed large pores at the middle part and a sponge layer at the lower part in the vertical direction.

17. A chemical mechanical polishing pad, characterized by, The chemical mechanical polishing pad buffer layer prepared by the preparation method of any one of claims 1-15 or the buffer layer of claim 16 is attached to a release layer.

18. The use of the chemical mechanical polishing pad of claim 17 in chemical mechanical polishing.

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