White pad for rough polishing of surface flatness of silicon wafer and production process thereof

Abstract

The application relates to the CMP polishing technical field and discloses a white pad for rough polishing of the flatness of a silicon wafer surface and a production process, which comprises a polyurethane-based rough polishing bottom layer, the surface of the polyurethane-based rough polishing bottom layer is provided with polishing grooves, the polishing grooves are cross pleat shaped, one side of the bottom end of the polyurethane-based rough polishing bottom layer is connected with a water conveying layer, the surface of the water conveying layer is provided with water conveying holes, the middle position of the water conveying holes is provided with spiral flow guide lines, the bottom end of the water conveying layer is connected with an inner lining layer, the outer edge of the inner lining layer is provided with an edge guard ring, the inner lining layer is arranged on the inner side of the edge guard ring, and the top end of the inner lining layer is connected with a positioning column. The white pad for rough polishing of the flatness of a silicon wafer surface and the production process can efficiently convey polishing liquid from the center to the edge in a directional manner, can quickly remove the friction heat in the center area, can realize uniform distribution of the polishing liquid on the silicon wafer surface, and can solve the polishing defects caused by uneven temperature of the existing white pad.

Description

Technical Field

[0001] This invention relates to the field of CMP polishing technology, and more particularly to a white pad and its manufacturing process for rough polishing of silicon wafer surfaces to improve surface flatness. Background Technology

[0002] Chemical mechanical polishing (CMP) is a core process in semiconductor manufacturing for achieving global planarization of silicon wafers. In advanced processes, the precision with which it controls the flatness and roughness of the silicon wafer surface directly determines the yield and performance of the chip. White pads, as key consumables in the CMP process, serve a dual function of mechanical polishing and slurry conduction. Especially in the rough polishing stage of silicon wafers, white pads must possess both high-efficiency material removal capabilities and stable slurry distribution performance to meet the stringent surface quality requirements of silicon wafers in advanced processes of 14nm and below.

[0003] However, existing white pads used for rough polishing of silicon wafers face numerous technical bottlenecks in practical applications. On the one hand, uneven heat distribution due to friction during polishing results in a significantly higher temperature in the central area compared to the edges, leading to insufficient thermal stability of the polyurethane substrate in the white pad. This, in turn, causes uneven global removal rate and deterioration of surface smoothness in the silicon wafer. On the other hand, the existing white pads lack coordination between water supply design and structural strength. Either the polishing fluid stagnates in the center or is insufficiently supplied at the edges, or the braided layer has poor tensile strength and is prone to separation between layers. This makes it impossible to simultaneously achieve the dual requirements of efficient water supply and heat dissipation, as well as resistance to deformation and wear, severely restricting the stability of the rough polishing process and the yield of silicon wafers. Summary of the Invention

[0004] The technical problem to be solved by this invention is that the existing technology has the disadvantage of high center temperature of white pads. To address this, we propose a white pad and its production process for rough polishing of silicon wafer surface flatness.

[0005] To achieve the above objectives, this application adopts the following technical solution: a white pad for coarse polishing of silicon wafer surface flatness, comprising a polyurethane-based coarse polishing underlayer, the surface of which is provided with polishing grooves, the polishing grooves being cross-shaped pleats, a water-conducting layer connected to one side of the bottom end of the polyurethane-based coarse polishing underlayer, water-conducting holes provided on the surface of the water-conducting layer, a spiral guide pattern provided in the middle of the water-conducting holes, an inner liner connected to the bottom end of the water-conducting layer, an edge guard ring provided on the outer edge of the inner liner, the inner liner being located inside the edge guard ring, a positioning post connected to the top end of the inner liner, a connecting layer provided on the upper surface of the inner liner, a support rib provided on the outer side of the connecting layer, multiple sets of support ribs provided, a woven guide layer provided between the multiple sets of inner liner layers, a polyurethane-based coarse polishing top layer connected to the bottom end of the inner liner, and the water-conducting layer, connecting layer, and inner liner layer wrapped between the polishing grooves and the polyurethane-based coarse polishing top layer.

[0006] Preferably, the positioning post on the upper surface of the inner lining corresponds to the water delivery hole on the surface of the water delivery layer, the positioning post is embedded inside the water delivery hole, and the woven flow guide layer, support rib and connecting layer are sandwiched between the water delivery layer and the inner lining.

[0007] Preferably, the water conveying layer is formed by pressing cotton, linen, and palm fibers, and the spiral guide pattern is formed by pressing and forming a spiral pattern on its surface, with the spiral pattern used for water conveying and guiding.

[0008] Preferably, the braided flow guide layers are woven with transverse braided lines, and the braiding density of the transverse braided lines increases with the radius, becoming more compact, and the braiding density increases closer to the connecting layer.

[0009] Preferably, the woven flow guide layer is disposed between the support ribs. The closer the woven flow guide layer is to the support rib, the lower the density of the woven flow guide layer. The closer the woven flow guide layer is to the middle position, the higher the density of the woven flow guide layer. The gaps on both sides of the woven flow guide layer are large, and the gaps are small closer to the middle position of the woven flow guide layer.

[0010] Preferably, the inner side of the woven flow guide layer and the support rib is connected to the connecting layer, and the support rib is a ring-shaped support made of palm fiber that fits into the loosely woven area at the edge of the woven flow guide layer.

[0011] Preferably, the edge of the inner lining is wrapped with an edge guard ring, the edge guard ring being thicker than the inner lining, the inner lining being embedded inside the edge guard ring, and the inner lining being flush with the upper surface of the edge guard ring.

[0012] The polyurethane-based coarse polishing top layer covers the surface of the edge guard ring, and a polishing groove is formed on the outer side of the polyurethane-based coarse polishing top layer. The polishing groove is used to guide the lubricant.

[0013] The production process of white pads used for rough polishing of silicon wafer surfaces includes the following steps: S1: Cotton and linen used to prepare the water-conducting layer are placed in a 5%-8% NaOH solution and boiled at 80-90℃ for 30-60 minutes to remove grease. Palm fibers of uniform length (10-20cm) are selected, hard stems are removed, and the fibers are carded into a continuous fiber web using a carding machine. S2: Palm fibers are placed in a 2%-3% pectinase solution and treated at 50-60℃ for 2-3 hours to remove pectin. After that, they are dried for later use. S3: The dried palm fibers are repeatedly rinsed with water until neutral and dried at 60-80℃ until the moisture content is <10%. The layers of cotton and linen and palm fibers are stacked alternately and pressed into a mold. The stacked cotton and linen and palm fibers are placed in a mold and pressed at 120-150℃ and 5-10MPa for 15-30 minutes. The heat is used to solidify the inter-fiber gum and simultaneously press out the spiral pattern.

[0014] Preferably, S4: The braided flow guide layer and the transverse braided threads are formed by interlacing cotton, linen and palm fiber. During weaving, from the central area connecting layer to the edge support ribs, the radius of the transverse braided threads is increased by 15%-20% for every 5mm increase in braiding density. At the same time, the braiding density of the flow guide layer gradually increases from the edge support ribs to the middle position. That is, the closer the flow guide layer is to the support ribs, the lower the braiding density and the larger the gaps. The closer the flow guide layer is to the middle position, the higher the braiding density and the smaller the gaps.

[0015] The technical effects and advantages of this invention are as follows:

[0016] In this invention, the polishing slurry can be efficiently and directionally delivered from the center to the edge, which can quickly remove the frictional heat generated in the central area and achieve uniform distribution of the polishing slurry on the silicon wafer surface, solving the polishing defects caused by uneven temperature in existing white pads. At the same time, the high water absorption of cotton and linen ensures the storage and conduction of the polishing slurry, and the strong toughness of palm fiber and the tightly woven design in the center greatly enhance the tensile strength of the white pad, effectively resisting the mechanical stress during the polishing process, extending the overall life of the white pad, further strengthening the connection stability of each layer structure, avoiding polishing slurry leakage and edge damage, and ensuring the continuity of the rough polishing process and the consistency of silicon wafer surface quality from a structural level. Attached Figure Description

[0017] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0018] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0019] Figure 2 This is a schematic diagram of the water conveying layer and spiral guide pattern of the present invention;

[0020] Figure 3 This is a schematic diagram of the structure of the inner lining and positioning post of the present invention;

[0021] Figure 4 This is a top view schematic diagram of the woven flow guide layer and support ribs of the present invention;

[0022] Figure 5 This is a schematic diagram of the supporting ribs and connecting layer of the present invention;

[0023] Figure 6 This is a schematic diagram of the structure of the braided flow guide layer and the transverse braided lines of the present invention;

[0024] Figure 7 This is an exploded structural diagram of the present invention.

[0025] Legend: 1. Polyurethane-based rough polished bottom layer; 2. Polishing groove; 3. Water delivery layer; 4. Water delivery hole; 5. Spiral guide pattern; 6. Inner lining layer; 7. Positioning post; 8. Braided guide layer; 9. Support rib; 10. Connecting layer; 11. Edge guard ring; 12. Horizontal braided line; 13. Polyurethane-based rough polished top layer. Detailed Implementation

[0026] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0027] Reference Figure 1-7 As shown, this invention provides a technical solution: a white pad for rough polishing of silicon wafer surface flatness, comprising a polyurethane-based rough polishing underlayer 1, wherein the surface of the polyurethane-based rough polishing underlayer 1 is provided with polishing grooves 2, the polishing grooves 2 being cross-shaped pleats, which not only optimizes the storage and distribution of polishing slurry, but also increases the consistency of contact with the silicon wafer through the uniform arrangement of the grooves, solving the problems of uneven polishing rate and poor silicon wafer surface flatness caused by local accumulation or lack of polishing slurry in traditional white pads. A water supply layer 3 is connected to one side of the bottom end of the polyurethane-based rough polishing underlayer 1, and water supply holes 4 are provided on the surface of the water supply layer 3, wherein the middle of the water supply holes 4 is located at... The device is equipped with a spiral guide pattern 5. The water delivery layer 3 is made of cotton, linen, and palm fiber. The high water absorption of cotton and linen can efficiently store polishing liquid, while the toughness of palm fiber ensures that the water delivery layer 3 is not easily deformed during long-term polishing operations. This solves the defects of structural collapse or water delivery capacity reduction after a single material absorbs water. The spiral guide pattern 5 is formed by pressing and has a spiral pattern on its surface. The spiral pattern is used for water delivery and guidance. When the white pad rotates, the spiral pattern can force the polishing liquid to flow from the center to the edge, which specifically solves the industry pain point of polishing liquid retention and heat dissipation difficulties in the central area, and significantly reduces the problems of polishing liquid failure and white pad aging caused by high temperature in the center.

[0028] The bottom end of the water delivery layer 3 is connected to an inner liner 6. An edge guard ring 11 is provided on the outer edge of the inner liner 6. The inner liner 6 is located inside the edge guard ring 11. The edge of the inner liner 6 is wrapped with the edge guard ring 11. The thickness of the edge guard ring 11 is greater than the thickness of the inner liner 6. The inner liner 6 is embedded inside the edge guard ring 11, and the inner liner 6 is flush with the upper surface of the edge guard ring 11. The thickened design of the edge guard ring 11 strengthens the structural strength of the white pad edge, avoids edge damage and delamination due to stress during polishing, and solves the problem of short overall lifespan caused by easy wear of the edge of traditional white pads.

[0029] The top of the inner lining layer 6 is connected to a positioning post 7. A connecting layer 10 is provided on the upper surface of the inner lining layer 6. The positioning post 7 on the upper surface of the inner lining layer 6 corresponds to the water inlet 4 opened on the surface of the water delivery layer 3. The positioning post 7 is embedded into the interior of the water inlet 4. The woven flow guide layer 8, the support ribs 9, and the connecting layer 10 are sandwiched between the water delivery layer 3 and the inner lining layer 6. The support ribs 9 are provided on the outer side of the connecting layer 10. The woven flow guide layer 8 is disposed between the support ribs 9. The closer the woven flow guide layer 8 is to the support ribs 9, the lower the woven density. The closer the woven flow guide layer 8 is to the middle position of the woven flow guide layer 8, the higher the woven density. The gaps on both sides of the woven flow guide layer 8 are large, and the gaps closer to the middle position of the woven flow guide layer 8 are small. The inner sides of the woven flow guide layer 8 and the support ribs 9 are connected to the connecting layer 10. A ring-shaped support made of palm fiber fits into the loosely woven area at the edge of the woven flow guide layer 8. Multiple sets of support ribs 9 are provided, and woven flow guide layers 8 are arranged between the multiple sets of inner lining layers 6. A polyurethane-based coarse polished top layer 13 is connected to the bottom end of the inner lining layer 6. The polyurethane-based coarse polished top layer 13 covers the surface of the edge guard ring 11. A polishing groove 2 is formed on the outer surface of the polyurethane-based coarse polished top layer 13. The polishing groove 2 is used to guide the lubricant. The water delivery layer 3, the connecting layer 10, and the inner lining layer 6 are wrapped between the polishing groove 2 and the polyurethane-based coarse polished top layer 13. Transverse braided lines 12 are woven between the woven flow guide layers 8. The density of the transverse braided lines 12 increases with the radius, becoming tighter, and the closer to the connecting layer 10, the greater the braiding density of the transverse braided lines 12.

[0030] Working Principle: In semiconductor manufacturing, polishing the silicon wafer surface for flatness is a critical process. This process primarily utilizes a white pad as a polishing medium to precisely process the silicon wafer surface. Specifically, the polyurethane-based rough polishing underlayer 1 of the white pad is kept in stable contact with the silicon wafer surface using polishing equipment. Under the combined action of mechanical pressure and relative motion, the abrasive particles on the white pad surface uniformly polish the silicon wafer surface. Simultaneously, a polishing slurry with a specific formulation is continuously added to the system. This slurry not only provides cooling and lubrication but also promotes the chemical mechanical polishing reaction. However, existing white pads have a significant technical drawback during polishing: due to uneven distribution of frictional heat and differences in heat dissipation conditions, the temperature in the central region of the white pad is significantly higher than that in the edge region. This temperature gradient causes several problems: firstly, the temperature difference leads to regional variations in the polishing rate; secondly, it affects the uniformity of the chemical reaction in the polishing slurry; and most importantly, it significantly reduces the flatness and roughness consistency of the silicon wafer surface, severely impacting the final product quality and process stability. To address this technical challenge, an innovative solution is proposed: a polishing groove structure 2 is created on the surface of the polyurethane-based rough polishing underlayer 1. This design optimizes the flow path and distribution of the polishing slurry. Specifically, it enhances the permeability of the polishing slurry in the central area and improves the retention effect in the edge area, thereby establishing a more balanced heat transfer mechanism and ultimately achieving a uniform temperature distribution throughout the polishing area.

[0031] During the polishing process, to improve the flow of the polishing slurry and ensure polishing quality, one side of the polyurethane-based coarse polishing top layer 13 is connected to the main body of the polishing equipment via a fixed interface, while the polyurethane-based coarse polishing bottom layer 1 is in direct contact with the silicon wafer surface. As the polishing device rotates, the polyurethane-based coarse polishing top layer 13 is driven to rotate, which in turn drives the edge guard ring 11 to rotate synchronously via mechanical linkage. To avoid uneven heat dissipation due to excessively high central area temperature during polishing, the entire white pad must be completely immersed in the polishing slurry at the beginning of the polishing process, until the slurry fully penetrates the internal structure of the white pad.

[0032] As the polyurethane-based coarse polishing top layer 13 continues to rotate, the polishing liquid stored in the white pad gradually permeates from the center area to the outside under the action of centrifugal force. When the polishing liquid in the connecting layer 10, the support rib 9 and the braided flow guide layer 8 migrates to the outside with the rotation, the polishing liquid inside the connecting layer 10 preferentially permeates to the side of the braided flow guide layer 8, while the liquid in the braided flow guide layer 8 further flows to the side of the inner liner layer 6. Finally, the inner liner layer 6 separates the polishing liquid from the white pad under the action of centrifugal force. In this process, the polishing liquid forms a dynamic flow path inside the white pad. When flowing, it continuously absorbs and carries away the heat generated by friction, achieving efficient cooling.

[0033] To address the core issue of high center temperature, when the polishing fluid inside the connecting layer 10 penetrates towards the braided guide layer 8, the uneven weave density of the braided guide layer 8 results in variations in the size of its internal pores. Consequently, the volume of polishing fluid immersed within these pores also differs. As the connecting layer 10 rotates, the polishing fluid preferentially flows towards the area with lower weave density, creating a trend where the liquid gradually moves towards the support rib 9. At this point, the polishing fluid rapidly diffuses from the gap between the braided guide layer 8 and the transverse braided lines 12 towards the edge support rib 9. On one hand, as a large amount of polishing fluid flows through the high-temperature central region, it efficiently absorbs and transfers frictional heat, reducing the temperature difference between the center and the edge, preventing the white pad from softening due to high temperatures and causing pore size expansion, thus ensuring the consistency of the polishing process. On the other hand, the weave density of the transverse braided lines 12 gradually increases with the radius, with a looser gap in the middle area facilitating rapid convergence of water flow during rotation and reducing stagnation, while the narrowing of the outer gaps directs the liquid towards the edge area near the support rib 9. This design not only prevents polishing fluid from accumulating in the middle, but also promotes more even coverage of the white pad surface with the liquid, improving the overall uniformity and efficiency of polishing.

[0034] Furthermore, the relatively tight weave structure in the middle region of the braided flow guide layer 8 provides it with basic strength. Simultaneously, thanks to the effective support of the support ribs 9, both enhance the overall tensile strength of the material, enabling the structure to more effectively resist rotational tension, polishing pressure, and other complex mechanical stress impacts generated during polishing operations. This significantly reduces the risk of deformation of the braided flow guide layer 8 under stress, ensuring process stability and product reliability.

[0035] On the other hand, during the polishing process, to further prevent potential deformation of the white pad, the positioning post 7 is combined with the water inlet 4. This embedded method effectively increases the compactness of the overall structure, making the internal connection more stable. At the same time, in conjunction with the setting of the weaving density of the transverse braided lines 12, the tensile strength of the white pad is further enhanced from multiple directions.

[0036] The manufacturing process for white pads used in the rough polishing of silicon wafer surfaces includes the following steps:

[0037] S1: Place the cotton and linen used to prepare the water transport layer 3 into a 5%-8% NaOH solution and boil it at 80-90℃ for 30-60 minutes to remove the grease. Select palm fibers with a uniform length of 10-20cm, remove the hard stems, and comb them into a continuous fiber web using a carding machine.

[0038] S2: Place the palm fiber in a 2%-3% pectinase solution and treat it at 50-60℃ for 2-3 hours to remove the pectin. Then dry it for later use.

[0039] S3: After drying, the palm fiber is repeatedly rinsed with clean water until neutral, and then dried at 60-80℃ until the moisture content is <10%. The cotton, linen and palm fibers are then pressed in an alternating manner. The stacked cotton, linen and palm fibers are placed in a mold and pressed at 120-150℃ and 5-10MPa for 15-30 minutes. The heat is used to solidify the glue between the fibers and at the same time, the spiral pattern is pressed out.

[0040] S4: The braided flow guide layer 8 and the transverse braided lines 12 are formed by interlacing cotton, linen and palm fiber. During the weaving process, from the central area connecting layer 10 to the edge support rib 9, the radius of the transverse braided lines 12 is increased by 15%-20% for every 5mm increase in the weaving density. At the same time, the weaving density of the braided flow guide layer 8 gradually increases from the edge support rib 9 to the middle position. That is, the closer the braided flow guide layer 8 is to the support rib 9, the lower the braiding density and the larger the gap. The closer the braided flow guide layer 8 is to the middle position, the higher the weaving density and the smaller the gap.

[0041] S5: Modified polyurethane is used as raw material, and polyimide nanofibers are added at a mass ratio of 5%-8% to enhance toughness. The raw material is injected into a mold with a cross-shaped pleated cavity and foamed at 40-45℃ to form a cross-shaped pleated structure with polished grooves 2 on the surface of the polyurethane-based rough polished bottom layer 1.

[0042] S6: The inner lining layer 6 is made of glass fiber reinforced polyurethane material and is formed by injection molding. The surface is reserved with mounting positions for positioning posts 7 and water inlet holes 4.

[0043] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A white pad for rough polishing of silicon wafer surface flatness, characterized in that, The system includes a polyurethane-based coarse polishing underlayer. The surface of the polyurethane-based coarse polishing underlayer has polishing grooves formed by cross-shaped pleats. A water-conducting layer is connected to one side of the bottom end of the polyurethane-based coarse polishing underlayer. Water-conducting holes are formed on the surface of the water-conducting layer, and a spiral guide pattern is provided in the center of each water-conducting hole. An inner liner is connected to the bottom end of the water-conducting layer. An edge guard ring is provided on the outer edge of the inner liner, and the inner liner is located inside the edge guard ring. A positioning post is connected to the top end of the inner liner. A connecting layer is provided on the upper surface of the inner liner, and multiple sets of support ribs are provided on the outer side of the connecting layer. A woven flow guide layer is provided between the inner lining layer and the bottom end of the inner lining layer is connected to a polyurethane-based coarse polished top layer. The water delivery layer, the connecting layer, and the inner lining layer are wrapped between the polishing groove and the polyurethane-based coarse polished top layer. The woven flow guide layer is woven with transverse braided lines. The density of the transverse braided lines increases with the radius and decreases as they approach the connecting layer. The woven flow guide layer is located between the support ribs. The closer the woven flow guide layer is to the support rib, the lower its density. The closer it is to the center of the woven flow guide layer, the higher its density. The gaps on both sides of the woven flow guide layer are large, and the gaps are small as they approach the center of the woven flow guide layer.

2. The white pad for rough polishing of silicon wafer surface flatness according to claim 1, characterized in that: The positioning posts on the upper surface of the inner lining layer correspond to the water delivery holes on the surface of the water delivery layer. The positioning posts are embedded inside the water delivery holes. The woven flow guide layer, support ribs, and connecting layer are sandwiched between the water delivery layer and the inner lining layer.

3. The white pad for rough polishing of silicon wafer surface flatness according to claim 1, characterized in that: The water conveying layer is formed by pressing cotton, linen, and palm fibers. The spiral guide pattern is formed by pressing, and its surface is provided with spiral patterns. The spiral patterns are used for water conveying and guiding.

4. The white pad for rough polishing of silicon wafer surface flatness according to claim 1, characterized in that: The inner sides of the woven flow guide layer and the support rib are connected to the connecting layer. The support rib is a ring-shaped support made of palm fiber, which fits into the loosely woven area at the edge of the woven flow guide layer.

5. The white pad for rough polishing of silicon wafer surface flatness according to claim 1, characterized in that: The edge of the inner lining is wrapped with an edge guard ring, the edge guard ring being thicker than the inner lining, the inner lining being embedded inside the edge guard ring, and the inner lining being flush with the upper surface of the edge guard ring.

6. The white pad for rough polishing of silicon wafer surface flatness according to claim 1, characterized in that: The polyurethane-based coarse polishing top layer covers the surface of the edge guard ring, and a polishing groove is formed on the outer side of the polyurethane-based coarse polishing top layer. The polishing groove is used to guide the lubricant.

7. The manufacturing process for the white pad used for rough polishing of silicon wafer surface flatness according to any one of claims 1-6, characterized in that: Includes the following steps: S1: Place the cotton and linen used to prepare the water transport layer into a 5%-8% NaOH solution and boil it at 80-90℃ for 30-60 minutes to remove the grease. Select palm fibers with a uniform length of 10-20cm, remove the hard stems, and comb them into a continuous fiber web using a carding machine. S2: Place the palm fiber in a 2%-3% pectinase solution and treat it at 50-60℃ for 2-3 hours to remove the pectin, then dry it for later use. S3: After drying, the palm fiber is repeatedly rinsed with clean water until neutral, and then dried at 60-80℃ until the moisture content is <10%. The cotton, linen and palm fibers are then pressed in an alternating manner. The stacked cotton, linen and palm fibers are placed in a mold and pressed at 120-150℃ and 5-10MPa for 15-30 minutes. The heat is used to solidify the glue between the fibers and at the same time, the spiral pattern is pressed out.

8. The production process of the white pad for rough polishing of silicon wafer surface flatness according to claim 7, characterized in that: It also includes the following steps: S4: The braided flow guide layer and the transverse braided lines are formed by interweaving cotton, linen and palm fiber. During weaving, from the central area connecting layer to the edge support ribs, the radius of the transverse braided lines is increased by 15%-20% for every 5mm increase in braiding density. At the same time, the braiding density of the flow guide layer gradually increases from the edge support ribs to the middle position. That is, the closer the flow guide layer is to the support ribs, the lower the braiding density and the larger the gaps. The closer the flow guide layer is to the middle position, the higher the braiding density and the smaller the gaps.

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