Low-hardness grinding pad and preparation method thereof

Abstract

The invention provides a low-hardness grinding pad and a preparation method thereof. The preparation method comprises the steps that a base material layer, a hot melting bonding layer and an upper pad layer are provided; the base material layer is pretreated, a buffer layer with the shore hardness smaller than 50 SHA is obtained, then a hot melting bonding layer is attached to the surface of the buffer layer, and primary hot pressing is carried out; an upper cushion layer is attached to the surface of the hot melting bonding layer, secondary hot pressing is carried out, then window manufacturing is carried out on the upper cushion layer to form at least one window, and then grooving treatment is carried out to form a plurality of grooves; and an induction bonding layer is provided, the induction bonding layer is attached to the surface of the side, away from the hot melting bonding layer, of the buffer layer, third-time hot pressing is carried out, and the low-hardness grinding pad is obtained. The hardness of the grinding pad is reduced, and then surface scratches or defects in the wafer polishing process are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of wafer grinding and relates to a low-hardness grinding pad and a preparation method thereof. Background Art

[0002] During the wafer grinding process, the wafer and the grinding pad rotate relative to each other to remove the deposited materials on the excess or uneven parts of the silicon wafer surface. At the same time, the diamond dresser located directly above the grinding pad will also be subjected to downward pressure, so that it is in full contact with the grinding pad, ensuring that the surface roughness of the grinding pad is constant, so as to effectively remove the residual grinding fluid and excess silicon material between the grooves on the wafer surface.

[0003] The interaction between the wafer, the retaining ring and the grinding pad jointly affects the number of surface defects of the wafer after grinding. If the grinding pad is hard as a whole, it will cause scratches on the wafer surface, defects and other problems. At present, the industry generally improves the synthetic formula of the upper layer of the grinding pad (the layer of the grinding pad that contacts the wafer) to reduce the hardness of the upper layer of the grinding pad and adjust the overall hardness of the grinding pad. However, in the preparation process of the upper layer material of the grinding pad, it is necessary to control multiple process parameters in order to select the material formula of the optimal upper layer pad. From formula improvement to the production of finished materials, it takes a long time, the overall cost is high, and it is inconvenient to operate. Therefore, it is necessary to find other methods that can adjust the hardness of the finished material to simplify the operation and improve production efficiency. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a low-hardness grinding pad and a preparation method thereof, which reduces the hardness of the overall grinding pad and solves the problem of wafer surface scratches and defects caused by the high hardness of the grinding pad during the chemical polishing process of the wafer.

[0005] In a first aspect, the present invention provides a method for preparing a low-hardness polishing pad, the preparation method comprising:

[0006] Providing a substrate layer, a hot melt adhesive layer and an upper cushion layer;

[0007] Pre-treating the substrate layer to obtain a buffer layer with a Shore hardness of less than 50 SHA, and then laminating a hot melt adhesive layer on the surface of the buffer layer and performing a hot pressing operation;

[0008] The upper cushion layer is attached to the surface of the hot-melt adhesive layer, and is subjected to secondary hot pressing, and then the upper cushion layer is subjected to window processing to form at least one window, and then a groove processing is performed to form a plurality of grooves;

[0009] An induction bonding layer is provided, and the induction bonding layer is attached to a surface of a buffer layer away from the hot-melt bonding layer, and hot pressing is performed three times to obtain a low-hardness polishing pad.

[0010] The present invention provides a method for preparing a low-hardness grinding pad, which is simple to operate and low in cost. By reducing the hardness of the buffer layer, the hardness of the overall grinding pad is effectively adjusted, and product surface defects are reduced, thereby improving the yield of finished products.

[0011] As a preferred technical solution of the present invention, the material of the substrate layer is polyester non-woven fabric.

[0012] Preferably, the material of the hot melt adhesive layer is a hot melt adhesive layer.

[0013] Preferably, the material of the upper cushion layer is polyurethane.

[0014] Preferably, the material of the inductive adhesive layer is a pressure-sensitive double-sided adhesive layer.

[0015] As a preferred technical solution of the present invention, the pretreatment method includes etching or embossing with abrasive.

[0016] Preferably, the average particle size of the abrasive is 25 to 350 nm, for example, 25 nm, 30 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm or 350 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, after the pretreatment, the roughness of the buffer layer is 2 to 4 μm, for example, it can be 2 μm, 2.3 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm or 4 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] As a preferred technical solution of the present invention, the temperature of the primary hot pressing is 90-120°C, for example, it can be 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] Preferably, the pressure of the primary hot pressing is 3 to 4 bar, for example, it can be 3 bar, 3.1 bar, 3.2 bar, 3.3 bar, 3.4 bar, 3.5 bar, 3.6 bar, 3.7 bar, 3.8 bar, 3.9 bar or 4 bar, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, after the one hot pressing, the compression rate of the buffer layer is 2.1% to 4.5%, for example, it can be 2.1%, 2.2%, 2.3%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.6%, 4%, 4.3% or 4.5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] It should be noted that the compression ratio in the present invention refers to (thickness before compression-thickness after compression) / thickness before compression.

[0022] As a preferred technical solution of the present invention, the temperature of the secondary hot pressing is 90-130°C, for example, it can be 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, the pressure of the secondary hot pressing is 2 to 5 bar, for example, it can be 2 bar, 2.2 bar, 2.5 bar, 2.8 bar, 3 bar, 3.5 bar, 3.8 bar, 4 bar, 4.5 bar, 4.8 bar or 5 bar, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, after the secondary hot pressing, the compression rate of the buffer layer is 1.5% to 3.5%, for example, it can be 1.5%, 1.6%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.2% or 3.5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] As a preferred technical solution of the present invention, the temperature of the three hot pressings is 100-120°C, for example, it can be 100°C, 105°C, 108°C, 110°C, 112°C, 115°C, 118°C or 120°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] Preferably, the pressure of the three hot pressings is 3 to 4 bar, for example, it can be 3 bar, 3.1 bar, 3.2 bar, 3.3 bar, 3.4 bar, 3.5 bar, 3.6 bar, 3.7 bar, 3.8 bar, 3.9 bar or 4 bar, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, after the three hot pressings, the compression rate of the buffer layer is 0.5% to 1.5%, for example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 1%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] As a preferred technical solution of the present invention, the window is made using a cutting device.

[0029] Preferably, the maximum linear length of the orthographic projection of the window on the plane where the upper cushion layer is located is 0.6 to 1 cm, for example, it can be 0.6 cm, 0.65 cm, 0.7 cm, 0.75 cm, 0.8 cm, 0.95 cm, 0.9 cm, 0.95 cm or 1 cm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, the grooving process uses a cutting tool.

[0031] Preferably, the groove is in a circular, rectangular, U-shaped or tree-shaped shape.

[0032] Preferably, the depth of the groove is 350-480 μm, for example, 350 μm, 360 μm, 300 μm, 400 μm, 420 μm, 440 μm, 450 μm, 460 μm, 470 μm or 480 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] As a preferred technical solution of the present invention, the preparation method further comprises: blowing and cleaning the low-hardness polishing pad to remove residues on the surface of the upper pad layer and in the grooves.

[0034] Preferably, the purge cleaning uses high-pressure gas with a flow rate of 20 to 45 L / min. The flow rate of the high-pressure gas can be, for example, 20 L / min, 23 L / min, 25 L / min, 28 L / min, 30 L / min, 35 L / min, 38 L / min, 40 L / min, 43 L / min or 45 L / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the preparation method further comprises: after the pretreatment is completed, testing the material thickness, compression rate, roughness and hardness of the buffer layer.

[0036] Preferably, the preparation method further comprises: after completing the three hot pressings, detecting whether the low hardness polishing pad is deformed, and performing a secondary detection on the thickness, compression rate, roughness and hardness of the low hardness polishing pad.

[0037] In a second aspect, the present invention provides a low-hardness polishing pad, which is prepared by the method for preparing a low-hardness polishing pad according to the first aspect.

[0038] As a preferred technical solution of the present invention, the hardness of the low-hardness polishing pad is 47-56SHA, for example, it can be 47SHA, 48SHA, 49SHA, 50SHA, 51SHA, 52SHA, 53SHA, 54SHA, 55SHA or 56SHA, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention provides a low-hardness polishing pad and a preparation method thereof. The low-hardness buffer pad is compounded to the polishing pad by interlayer hot pressing bonding, which greatly reduces the overall hardness of the polishing pad, reduces product surface defects, and improves the finished product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of surface defects of a wafer after being processed by the low-hardness grinding pad of Example 1.

[0042] Figure 2 Schematic diagram of surface defects of a wafer after being processed by the low-hardness polishing pad of Example 2.

[0043] Figure 3 Schematic diagram of surface defects of a wafer after being processed by the low-hardness grinding pad of Comparative Example 1.

[0044] Figure 4 Schematic diagram of surface defects of a wafer after being processed with the low-hardness grinding pad of Comparative Example 2. DETAILED DESCRIPTION

[0045] It should be understood that, in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "once", "twice", "three times" and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "once", "twice", "three times", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" and "several" mean two or more.

[0046] It should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0047] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0048] In a specific embodiment, the present invention provides a method for preparing a low-hardness polishing pad, the preparation method comprising:

[0049] S1: Provide a substrate layer, a hot melt adhesive layer, an upper cushion layer and an induction adhesive layer. The substrate layer is made of polyester non-woven fabric, the hot melt adhesive layer is made of hot melt adhesive layer, the upper cushion layer is made of polyurethane, and the induction adhesive layer is made of a pressure-sensitive double-sided adhesive layer.

[0050] S2: The substrate layer is etched or embossed using an abrasive with an average particle size of 25 to 350 nm to obtain a buffer layer with a Shore hardness of less than 50 SHA. After the etching or embossing treatment, the buffer layer is tested for material thickness, compression rate, roughness and hardness.

[0051] S3: Then, a hot melt adhesive layer is attached to the surface of the buffer layer, and a heat pressing is performed, wherein the temperature of the heat pressing is 90-120° C. and the pressure is 3-4 bar. After the heat pressing, the compression rate of the buffer layer is 2.1%-4.5%.

[0052] S4: attaching the cushion layer to the surface of the hot-melt adhesive layer and performing secondary hot pressing, wherein the temperature of the secondary hot pressing is 90-130° C., the pressure is 2-5 bar, and after the secondary hot pressing, the compression rate of the buffer layer is 1.5%-3.5%.

[0053] S5: Then, a cutting device is used to make a window on the upper cushion layer to form at least one window, and then a cutting tool is used to perform a grooving process to form a plurality of grooves. The maximum linear length of the orthographic projection of the window on the plane where the upper cushion layer is located is 0.6 to 1 cm. The shape of the groove is circular, rectangular, U-shaped or tree-shaped, and the depth is 350 to 480 μm.

[0054] S6: attaching the induction adhesive layer to the side of the buffer layer away from the hot melt adhesive layer, and performing three hot pressings to obtain a low hardness polishing pad. The temperature of the three hot pressings is 100-120° C., the pressure is 3-4 bar, and after the three hot pressings, the compression rate of the buffer layer is 0.5%-1.5%.

[0055] S7: Use high-pressure gas with a flow rate of 20 to 45 L / min to purge and clean the low-hardness polishing pad to remove residues on the surface of the upper pad layer and in the grooves.

[0056] S8: Check whether the low hardness polishing pad is deformed, and conduct secondary inspection on the thickness, compression rate, roughness and hardness of the low hardness polishing pad.

[0057] In another specific embodiment, the present invention provides a low-hardness polishing pad, which is prepared by the method for preparing a low-hardness polishing pad described in a specific embodiment. The hardness of the low-hardness polishing pad is 47-56 SHA.

[0058] Example 1

[0059] This embodiment provides a method for preparing a low-hardness polishing pad, which specifically comprises the following steps:

[0060] (1) providing a substrate layer, a hot melt adhesive layer, an upper cushion layer and an induction adhesive layer, wherein the substrate layer is made of polyester non-woven fabric, the hot melt adhesive layer is made of a hot melt adhesive layer, the upper cushion layer is made of polyurethane, and the induction adhesive layer is made of a pressure-sensitive double-sided adhesive layer;

[0061] (2) using an abrasive with an average particle size of 200 nm to emboss the substrate layer to obtain a buffer layer with a Shore hardness of less than 50 SHA, and then testing the material thickness, compression rate, roughness and hardness of the buffer layer;

[0062] (3) Then, a hot-melt adhesive layer is attached to the surface of the buffer layer, and a heat pressing is performed once, and the temperature of the heat pressing is 100° C. and the pressure is 4 bar. After the heat pressing once, the compression rate of the buffer layer is 3.2%;

[0063] (4) attaching a cushion layer to the surface of the hot-melt adhesive layer and performing secondary hot pressing. The temperature of the secondary hot pressing is 110° C. and the pressure is 4 bar. After the secondary hot pressing, the compression rate of the cushion layer is 1.8%;

[0064] (5) Then, a cutting device is used to make a window on the upper cushion layer to form at least one window, and the maximum linear length of the orthographic projection of the window on the plane where the upper cushion layer is located is 0.8 cm. Then, a cutting tool is used to perform grooving to form a plurality of circular grooves with a depth of 400 μm;

[0065] (6) laminating the induction adhesive layer to the side of the buffer layer away from the hot-melt adhesive layer, and performing hot pressing three times to obtain a low-hardness polishing pad, wherein the temperature of the three hot pressings is 110° C. and the pressure is 3 bar. After the three hot pressings, the compression rate of the buffer layer is 0.8%;

[0066] (7) Using high-pressure gas at a flow rate of 25 L / min to purge and clean the low-hardness polishing pad to remove residues on the surface and in the grooves of the upper pad layer;

[0067] (8) Check whether the low hardness polishing pad is deformed, and conduct secondary inspection on the thickness, compression rate, roughness and hardness of the low hardness polishing pad.

[0068] The low-hardness polishing pad prepared in this embodiment has a hardness of 47 SHA, a thickness of 1.62 mm, and an overall compression rate of 5.89%.

[0069] Example 2

[0070] This embodiment provides a method for preparing a low-hardness polishing pad, which specifically comprises the following steps:

[0071] (1) providing a substrate layer, a hot melt adhesive layer, an upper cushion layer and an induction adhesive layer, wherein the substrate layer is made of polyester non-woven fabric, the hot melt adhesive layer is made of a hot melt adhesive layer, the upper cushion layer is made of polyurethane, and the induction adhesive layer is made of a pressure-sensitive double-sided adhesive layer;

[0072] (2) etching the substrate layer with an abrasive having an average particle size of 100 nm to obtain a buffer layer with a Shore hardness of less than 50 SHA, and testing the thickness, compressibility, roughness and hardness of the buffer layer;

[0073] (3) Then, a hot-melt adhesive layer is attached to the surface of the buffer layer, and a heat pressing is performed once, wherein the temperature of the heat pressing is 120° C. and the pressure is 3 bar. After the heat pressing once, the compression rate of the buffer layer is 2.1%;

[0074] (4) attaching a cushion layer to the surface of the hot-melt adhesive layer and performing secondary hot pressing. The temperature of the secondary hot pressing is 120° C. and the pressure is 2.5 bar. After the secondary hot pressing, the compression rate of the cushion layer is 1.5%;

[0075] (5) Then, a cutting device is used to make a window on the upper cushion layer to form at least one window, and the maximum linear length of the orthographic projection of the window on the plane where the upper cushion layer is located is 0.6 cm. Then, a cutting tool is used to perform grooving to form a plurality of rectangular grooves with a depth of 450 μm;

[0076] (6) laminating the induction adhesive layer to the side of the buffer layer away from the hot-melt adhesive layer, and performing hot pressing three times to obtain a low-hardness polishing pad. The temperature of the three hot pressings is 100° C. and the pressure is 4 bar. After the three hot pressings, the compression rate of the buffer layer is 0.5%;

[0077] (7) Using high-pressure gas at a flow rate of 20 L / min to purge and clean the low-hardness polishing pad to remove residues on the surface and in the grooves of the upper pad;

[0078] (8) Check whether the low hardness polishing pad is deformed, and conduct secondary inspection on the thickness, compression rate, roughness and hardness of the low hardness polishing pad.

[0079] The low-hardness polishing pad prepared in this embodiment has a hardness of 56 SHA, a thickness of 1.63 mm, and an overall compression rate of 2.51%.

[0080] Example 3

[0081] This embodiment provides a method for preparing a low-hardness polishing pad, which specifically comprises the following steps:

[0082] (1) providing a substrate layer, a hot melt adhesive layer, an upper cushion layer and an induction adhesive layer, wherein the substrate layer is made of polyester non-woven fabric, the hot melt adhesive layer is made of a hot melt adhesive layer, the upper cushion layer is made of polyurethane, and the induction adhesive layer is made of a pressure-sensitive double-sided adhesive layer;

[0083] (2) using an abrasive with an average particle size of 100 nm to emboss the substrate layer to obtain a buffer layer with a Shore hardness of less than 50 SHA, and then testing the material thickness, compression rate, roughness and hardness of the buffer layer;

[0084] (3) Then, a hot-melt adhesive layer is attached to the surface of the buffer layer, and a heat pressing is performed once, wherein the temperature of the heat pressing is 90° C. and the pressure is 3.5 bar. After the heat pressing once, the compression rate of the buffer layer is 2.5%;

[0085] (4) attaching a cushion layer to the surface of the hot-melt adhesive layer and performing secondary hot pressing. The temperature of the secondary hot pressing is 130° C. and the pressure is 5 bar. After the secondary hot pressing, the compression rate of the cushion layer is 2%;

[0086] (5) Then, a cutting device is used to make a window on the upper cushion layer to form at least one window, and the maximum linear length of the orthographic projection of the window on the plane where the upper cushion layer is located is 1 cm. Then, a cutting tool is used to perform grooving to form a plurality of rectangular grooves with a depth of 480 μm;

[0087] (6) laminating the induction adhesive layer to the side of the buffer layer away from the hot-melt adhesive layer, and performing hot pressing three times to obtain a low-hardness polishing pad. The temperature of the three hot pressings is 110° C. and the pressure is 3.5 bar. After the three hot pressings, the compression rate of the buffer layer is 1%;

[0088] (7) Using high-pressure gas with a flow rate of 45 L / min to purge and clean the low-hardness polishing pad to remove residues on the surface and in the grooves of the upper pad;

[0089] (8) Check whether the low hardness polishing pad is deformed, and conduct secondary inspection on the thickness, compression rate, roughness and hardness of the low hardness polishing pad.

[0090] The low-hardness polishing pad prepared in this embodiment has a hardness of 50 SHA, a thickness of 1.85 mm, and an overall compression rate of 3.12%.

[0091] Comparative Example 1

[0092] This comparative example provides a method for preparing a polishing pad, which differs from Example 1 in that: in step (2), no pretreatment of the substrate layer is performed, the hardness of the buffer layer used is >50SHA, and the remaining preparation steps, materials, process parameters, etc. are the same as those in Example 1.

[0093] The hardness of the polishing pad prepared in this comparative example is 53SHA, the thickness is 1.62mm, and the overall compression rate is 3.5%.

[0094] Comparative Example 2

[0095] This comparative example provides a method for preparing a polishing pad, which differs from Example 2 in that: in step (2), no pretreatment of the substrate layer is performed, the hardness of the buffer layer used is >50SHA, and the remaining preparation steps, materials, process parameters, etc. are the same as those in Example 2.

[0096] The hardness of the polishing pad prepared in this comparative example is 62SHA, the thickness is 1.63mm, and the overall compression rate is 1.25%.

[0097] The present invention uses the grinding pads in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 to polish the wafer and detect the number of defects on the wafer surface. Figure 1 As shown, after polishing with the grinding pad of Example 1, the number of defects on the wafer surface is 10; Figure 2 As shown, after polishing with the grinding pad of Example 1, the number of defects on the wafer surface is 15; Figure 3 As shown in FIG. 1 , after polishing with the grinding pad of Example 1, the number of defects on the wafer surface is 65; Figure 4 As shown, after polishing with the polishing pad of Example 1, the number of defects on the wafer surface is 79. Compared with Comparative Examples 1 and 2, the low hardness polishing pads prepared in Examples 1 and 2 of the present invention can greatly reduce the number of surface defects after wafer polishing, and effectively improve product quality.

[0098] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a low hardness polishing pad, characterized in that: The preparation method comprises: Providing a substrate layer, a hot melt adhesive layer and an upper cushion layer; Pre-treating the substrate layer to obtain a buffer layer with a Shore hardness of less than 50 SHA, and then laminating a hot melt adhesive layer on the surface of the buffer layer and performing a hot pressing operation; The upper cushion layer is attached to the surface of the hot-melt adhesive layer, and is subjected to secondary hot pressing, and then the upper cushion layer is subjected to window processing to form at least one window, and then a groove processing is performed to form a plurality of grooves; An induction bonding layer is provided, and the induction bonding layer is attached to a surface of a buffer layer away from the hot-melt bonding layer, and hot pressing is performed three times to obtain a low-hardness polishing pad.

2. The preparation method according to claim 1, characterized in that: The material of the substrate layer is polyester non-woven fabric; Preferably, the material of the hot melt adhesive layer is a hot melt adhesive layer; Preferably, the material of the upper cushion layer is polyurethane; Preferably, the material of the inductive adhesive layer is a pressure-sensitive double-sided adhesive layer.

3. The preparation method according to claim 1 or 2, characterized in that: The pretreatment method includes etching or embossing with abrasive; Preferably, the average particle size of the abrasive is 25 to 350 nm; Preferably, after the pretreatment, the roughness of the buffer layer is 2-4 μm.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The temperature of the primary hot pressing is 90-120°C; Preferably, the pressure of the primary hot pressing is 3 to 4 bar; Preferably, after the first hot pressing, the compression rate of the buffer layer is 2.1% to 4.5%.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The temperature of the secondary hot pressing is 90-130°C; Preferably, the pressure of the secondary hot pressing is 2 to 5 bar; Preferably, after the secondary hot pressing, the compression rate of the buffer layer is 1.5% to 3.5%.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The temperature of the three heat pressings is 100-120°C; Preferably, the pressure of the three heat pressings is 3 to 4 bar; Preferably, after the three times of hot pressing, the compression rate of the buffer layer is 0.5% to 1.5%; Preferably, after the three times of hot pressing, the roughness of the upper cushion layer is 18-35 μm.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The window is made by using a cutting device; Preferably, the maximum linear length of the orthographic projection of the window on the plane where the upper cushion layer is located is 0.6 to 1 cm; Preferably, the grooving process uses a cutting tool; Preferably, the groove is circular, rectangular, U-shaped or tree-shaped; Preferably, the depth of the groove is 350-480 μm.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The preparation method further comprises: blowing and cleaning the low-hardness polishing pad to remove residues on the surface of the upper pad layer and in the grooves; Preferably, the purging cleaning uses high-pressure gas with a flow rate of 20 to 45 L / min; Preferably, the preparation method further comprises: after the pretreatment, testing the material thickness, compression rate, roughness and hardness of the buffer layer; Preferably, the preparation method further comprises: after completing the three hot pressings, detecting whether the low hardness polishing pad is deformed, and performing a secondary detection on the thickness, compression rate, roughness and hardness of the low hardness polishing pad.

9. A low hardness polishing pad, characterized in that: The low-hardness polishing pad is prepared by the preparation method of the low-hardness polishing pad according to any one of claims 1 to 8.

10. The low-hardness polishing pad according to claim 9, characterized in that: The hardness of the low-hardness polishing pad is 47-56 SHA.

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