Wafer adsorption device

Abstract

The embodiment of the utility model provides a wafer adsorption device. The wafer adsorption device comprises an adsorption body and a flexible film. The adsorption body comprises an adsorption surface and is provided with adsorption holes, and the adsorption holes penetrate through the adsorption surface. The flexible film is positioned on the adsorption surface and is provided with a through hole; wherein the through hole penetrates through the flexible film in the thickness direction of the flexible film, and the through hole is communicated with the adsorption hole. Therefore, when the adsorption body is used for grabbing the wafer, the adsorption body plays a role in supporting the wafer, and the wafer is adsorbed by the through holes in the flexible film, so that the flexible film is in direct contact with the wafer, and the problem that the wafer is scratched due to direct contact between the adsorption body and the wafer is solved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and more particularly to a wafer adsorption device. Background Technology

[0002] In the semiconductor manufacturing industry, vacuum pens are widely used as key tools in wafer processing, including quality inspection, wafer sorting, and cross-carrier transfer. Especially in the processing of ultra-thin wafers (thickness ≤200μm), due to the insufficient coverage of existing fully automated wafer processing equipment (<30%), a large number of production scenarios still rely on manual operation.

[0003] The current manual operation mode has significant technical drawbacks: operators need to use a vacuum pen to perform high-frequency contact gripping of the wafer (more than 200 times per shift), and this physical contact process is prone to generating mechanical scratches on the wafer surface. The microscopic damage caused by these mechanical scratches not only directly affects the product yield, but also causes pattern distortion in subsequent photolithography processes, ultimately leading to a decrease in the reliability of microelectronic devices. Utility Model Content

[0004] This application provides a wafer adsorption device that reduces the risk of scratching the wafer when gripping it, thereby at least partially solving the above-mentioned technical problems.

[0005] To achieve the above objectives, according to a first aspect of this application, a wafer adsorption device is provided, comprising an adsorption body and a flexible film. The adsorption body includes an adsorption surface and is provided with adsorption holes, the adsorption holes penetrating the adsorption surface. The flexible film is located on the adsorption surface and is provided with through holes. The through holes penetrate the flexible film along its thickness direction and communicate with the adsorption holes.

[0006] Optionally, the flexible membrane includes an adhesive layer and an antistatic layer, wherein the adhesive layer is located between the adsorption surface and the antistatic layer.

[0007] Optionally, the thickness of the antistatic layer is 40 micrometers to 60 micrometers.

[0008] Optionally, the thickness of the flexible membrane is 0.5 mm to 1.2 mm.

[0009] Optionally, the adsorption surface is further provided with protrusions, and a groove is provided between two adjacent protrusions. The flexible membrane is located on the protrusions, and the adsorption pore is connected to the through hole through the groove.

[0010] Optionally, the protrusion includes a plurality of first protrusions, the groove includes a first groove, the plurality of first protrusions extend along a first direction and are spaced apart along a second direction, a first groove is provided between adjacent first protrusions, and the first direction intersects the second direction.

[0011] Optionally, along the second direction, the size of the first protrusion is smaller than the size of the first groove.

[0012] Optionally, the protrusion further includes a second protrusion, which is arranged around a plurality of the first protrusions, and the first groove is also provided between the second protrusion and the first protrusion;

[0013] The groove further includes a second groove. Each of the first protrusions includes a first end and a second end opposite to each other. The first end of each of the first protrusions is connected to the second protrusion. The second groove is disposed between the second end of each of the plurality of first protrusions and the second protrusion. The second groove extends along the second direction and communicates with the plurality of first grooves.

[0014] Optionally, the adsorption hole penetrates the bottom of the second groove.

[0015] Optionally, the wafer adsorption device further includes a rod portion connected to the adsorption body, and the rod portion has a cavity inside, which communicates with the adsorption hole.

[0016] Optionally, the diameter of the adsorption pore is larger than the diameter of the through pore.

[0017] Optionally, the diameter of the through hole is 200 micrometers to 300 micrometers.

[0018] Optionally, the distribution density of the through holes is 15 holes / cm². 2 ~25 pieces / cm 2 .

[0019] In some embodiments of the wafer adsorption device of this application, a flexible film is added to the adsorption surface of the adsorption body. The flexible film has through holes, and the through holes are connected to the adsorption holes that penetrate the adsorption surface. Thus, when the adsorption body grips the wafer, the adsorption body supports the wafer, and the through holes on the flexible film adsorb the wafer, allowing the flexible film to directly contact the wafer, thereby improving the problem of wafer scratches caused by direct contact between the adsorption body and the wafer. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the planar structure of the wafer adsorption device provided in an exemplary embodiment of this application;

[0021] Figure 2This is a schematic diagram of a planar structure of an adsorption body provided in an exemplary embodiment of this application;

[0022] Figure 3 This is a schematic diagram of another planar structure of the adsorption body provided in an exemplary embodiment of this application;

[0023] Figure 4 This is a schematic diagram of the planar structure of the flexible membrane provided in an exemplary embodiment of this application;

[0024] Figure 5 The example embodiments provided in this application are along Figure 4 A schematic diagram of the cross-sectional structure obtained by the tangent line A-A'.

[0025] Explanation of reference numerals in the attached figures:

[0026] 100. Wafer adsorption device;

[0027] 11. Adsorption body; 111. Adsorption surface; 112. Adsorption pore; 113. First adsorption pore; 114. Second adsorption pore;

[0028] 121. Protrusion; 122. First protrusion; 123. Second protrusion;

[0029] 131. Groove; 132. First groove; 133. Second groove; 134. Middle groove; 135. Edge groove

[0030] 21. Flexible membrane; 211. Adhesive layer; 212. Antistatic layer; 213. Through hole; 214. First through hole; 215. Second through hole;

[0031] 31. Rod section;

[0032] X, the first direction; Y, the second direction. Detailed Implementation

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0034] Please see Figure 1This application provides a wafer adsorption device 100. During wafer quality inspection, sorting, and cross-carrier transfer processes, the wafer adsorption device 100 adsorbs the surface of the wafer (e.g., the functional surface of the wafer with device structures or the back side of the functional surface) to achieve wafer gripping. The wafer may include a single wafer or multiple wafers bonded together to form a bonded wafer.

[0035] Please see Figure 2 and Figure 3 The wafer adsorption device 100 includes an adsorption body 11. The adsorption body 11 includes an adsorption surface 111 and is provided with adsorption holes 112, which penetrate the adsorption surface 111. In this way, a vacuum is drawn through the adsorption holes 112 to form a negative pressure, thereby adsorbing the wafer onto the adsorption body 11.

[0036] The adsorption body 11 provides support for the wafer. In some embodiments, the adsorption body 11 may include a rigid material, including but not limited to rigid plastics, metals, and composite materials. For example, the adsorption body 11 may include a rigid plastic. Figure 1 As shown, the shape of the adsorption surface 111 can be a chamfered rectangle, but is not limited to this.

[0037] In some embodiments, please refer to Figure 1 The wafer adsorption device 100 also includes a rod 31. The rod 31 is connected to the adsorption body 11 to facilitate moving the wafer adsorption device 100 by holding the rod 31. A cavity (not shown in the figure) is provided inside the rod 31, and the cavity communicates with the adsorption hole 112. In this way, the adsorption hole 112 can communicate with the vacuum device through the cavity.

[0038] It should be noted that the end of the rod 31 away from the adsorption body 11 can be connected to a vacuum pumping device through a pipeline, so that the vacuum pumping device can draw a vacuum through the cavity and the adsorption hole.

[0039] In some embodiments, the rod portion 31 may be integrally formed with the adsorption body 11. When the rod portion 31 and the adsorption body 11 are integrally formed, the rod portion 31 may be integrally formed with the adsorption body 11, or the rod portion 31 may be detachably connected to the adsorption body 11.

[0040] In some embodiments, please refer to Figure 1 , Figure 4 and Figure 5The wafer adsorption device 100 also includes a flexible membrane 21. The flexible membrane 21 is located on the adsorption surface 111 and has through holes 213. The through holes 213 penetrate the flexible membrane 21 along its thickness direction and are connected to the adsorption holes 112. With this configuration, when the adsorption body 11 grasps the wafer, the through holes 213 on the flexible membrane 21 adsorb the wafer, allowing the flexible membrane 21 to directly contact the wafer. The flexibility of the flexible membrane 21 mitigates the problem of scratches on the wafer caused by direct contact between the adsorption body 11 and the wafer.

[0041] In some embodiments, the hardness of the surface of the flexible film 21 facing away from the adsorption body 11 is less than the hardness of the adsorption body 11, making the flexible film 21 flexible and reducing the risk of damage to the wafer when the flexible film 21 is in direct contact with the wafer.

[0042] In some embodiments, the flexible membrane 21 can be a single membrane to simplify the formation process of the flexible membrane 21. The flexible membrane 21 can be attached to the adsorption surface 111 by bonding or by bolt and nut fitting.

[0043] In some embodiments, the flexible membrane 21 may include at least one of a polyurethane layer and a silicone rubber layer. In an exemplary embodiment, the flexible membrane 21 includes a polyurethane layer, which makes the flexible membrane 21 flexible while having a certain mechanical strength, reducing the risk of deformation of the flexible membrane 21 under the negative pressure generated by a vacuum.

[0044] In some embodiments, the thickness of the flexible film 21 is 0.5 mm to 1.2 mm, so that the thickness of the flexible film 21 is within a suitable range, ensuring that the flexible film 21 protects the wafer when it comes into contact with the wafer, while reducing the manufacturing and installation difficulty of the flexible film 21.

[0045] In some embodiments, please refer to Figure 5 The flexible film 21 may include an adhesive layer 211 and an antistatic layer 212, with the adhesive layer 211 located between the adsorption surface 111 and the antistatic layer 212. In this way, the adhesive layer 211 fixes the antistatic layer 212 to the adsorption surface 111, reducing the risk of the antistatic layer 212 peeling off from the adsorption surface 111. Furthermore, during the contact between the flexible film 21 and the wafer, the antistatic layer 212 provides antistatic protection, reducing the risk of static electricity damaging the devices on the wafer.

[0046] In some embodiments, the antistatic layer 212 may include a polymer matrix and antistatic particles dispersed in the polymer matrix. In some embodiments, the polymer matrix may include at least one of a polyurethane layer and a silicone rubber layer. The antistatic particles may include conductive fillers such as carbon nanotubes, graphene, or metal nanoparticles.

[0047] In some embodiments, the antistatic layer 212 may further include a filler dispersed in a polymer matrix to improve the mechanical properties of the antistatic layer 212. The filler includes, but is not limited to, nano-silica.

[0048] In some embodiments, the thickness of the antistatic layer 212 can be 40 micrometers to 60 micrometers, so that it has a suitable thickness to ensure that it protects the wafer when it is in direct contact with the wafer, while reducing the manufacturing difficulty of the antistatic layer 212.

[0049] In some embodiments, the surface resistance of the antistatic layer 212 is 10 Ω. 6 Ω~10 8 Ω, to ensure the antistatic performance of the antistatic layer 212.

[0050] In some embodiments, the antistatic layer 212 can withstand a high temperature of 200°C to reduce the risk of deformation of the antistatic layer 212 under high temperature conditions and reduce the risk of the wafer falling off the flexible film 21.

[0051] In some embodiments, the adhesive layer 211 may include pressure-sensitive adhesive to improve the adhesion of the adhesive layer 211 and reduce the risk of the antistatic layer 212 peeling off from the adsorption body 11.

[0052] In some embodiments, the peel strength of the adhesive layer 211 is 3N / cm to 5N / cm to ensure that the adhesive layer 211 has suitable adhesion, reduce the risk of the adhesive layer 211 peeling off from the adsorption body 11 when the wafer adsorption device 100 picks up the wafer, and at the same time facilitate the easy peeling off of the flexible film 21 when replacing the flexible film 21.

[0053] In some embodiments, the diameter of the adsorption hole 112 may be larger than the diameter of the through hole 213, so that the diameter of the adsorption hole 112 is relatively larger, so as to facilitate rapid vacuuming through the adsorption hole 112 and reduce the pressure loss when air passes through the adsorption hole 112.

[0054] In some embodiments, the ratio of the diameter of the adsorption hole 112 to the diameter of the through hole 213 is greater than 1 and less than or equal to 3, so that the diameter of the adsorption hole 112 is within a suitable range, thereby improving the efficiency of vacuuming and maintaining a suitable vacuum level.

[0055] In some embodiments, please refer to Figure 2 The number of adsorption pores 112 can be one, which simplifies the manufacturing difficulty of the adsorption body 11.

[0056] In some embodiments, please refer to Figure 3 The number of adsorption pores 112 can be more than two to shorten the vacuuming time.

[0057] In some embodiments, please refer to Figure 2 and Figure 3 The shape of the adsorption pore 112 can be circular, but is not limited to this. In other embodiments, the shape of the adsorption pore 112 can be rectangular, elliptical, or irregular.

[0058] In some embodiments, please refer to Figure 1 and Figure 4 The number of through holes 213 can be multiple to ensure that the wafer is subjected to uniform force when multiple through holes 213 are used to adsorb the wafer, reducing the risk of damage due to uneven force on the wafer. Furthermore, using multiple through holes 213 to adsorb the wafer can also improve the adsorption force on the wafer.

[0059] In some embodiments, please refer to Figure 1 and Figure 4 Multiple through holes 213 can be arranged in an array along a first direction X and a second direction Y. The first direction X intersects the second direction Y. In some embodiments, the first direction X can be the length direction of the flexible membrane 21, and the second direction Y can be the width direction of the flexible membrane 21, but is not limited thereto. In other embodiments, the first direction X can be the width direction of the flexible membrane 21, and the second direction Y can be the length direction of the flexible membrane 21, but is not limited thereto.

[0060] In some embodiments, the through hole 213 may be circular, but is not limited thereto. In other embodiments, the through hole 213 may be rectangular, elliptical, or an irregular shape.

[0061] In some embodiments, the diameter of the plurality of through holes 213 may be the same to ensure that when the plurality of through holes 213 adsorb multiple adsorption sites on the wafer, the adsorption force on the multiple adsorption sites is the same.

[0062] In some embodiments, the diameters of at least two through holes 213 may be different to accommodate diverse adsorption requirements.

[0063] In some embodiments, please refer to Figure 1 and Figure 4 The multiple through holes 213 may include a first through hole 214 and a second through hole 215. The diameter of the second through hole 215 is larger than the diameter of the first through hole 214. The first through hole 214 may be located at the center of the flexible membrane 21, and the second through hole 215 may be adjacent to the edge of the flexible membrane 21.

[0064] In some embodiments, the diameter of the through hole 213 is 200 micrometers to 300 micrometers to ensure that the diameter of the through hole 213 is appropriate, improve the efficiency of vacuuming, maintain a suitable vacuum level, and ensure that the flexible film 21 can adsorb the wafer.

[0065] In some embodiments, the distribution density of the through holes 213 is 15 holes / cm². 2 ~25 pieces / cm 2 This ensures that the flexible film 21 can adhere to the wafer, while reducing the manufacturing difficulty of the flexible film 21.

[0066] In some embodiments, please refer to Figures 1 to 3 The adsorption surface 111 is also provided with protrusions 121, and grooves 131 are provided between two adjacent protrusions 121. The flexible membrane 21 is located on the protrusions 121, and the adsorption holes 112 are connected to the through holes 213 through the grooves 131. In this way, the protrusions 121 not only serve to support the flexible membrane 21, but also support the wafer when the flexible membrane 21 adsorbs the wafer. The supporting area of ​​the protrusions 121 is small to reduce the supporting area of ​​the adsorption body 11 on the wafer and reduce the risk of wafer damage during adsorption. Furthermore, the grooves 131 are larger in size, so that the vacuum degree in the grooves 131 tends to be the same when vacuuming. The adsorption holes 112 are connected to the through holes 213 through the grooves 131, so that the vacuum degree at different through holes 213 also tends to be the same, ensuring that the adsorption force on the wafer at different through holes 213 tends to be the same.

[0067] In some embodiments, please refer to Figure 2 and Figure 3 The protrusion 121 includes a plurality of first protrusions 122, and the groove 131 includes a first groove 132. The plurality of first protrusions 122 extend along a first direction X and are spaced apart along a second direction Y. A first groove 132 is provided between adjacent first protrusions 122. In this way, the plurality of first protrusions 122 can provide uniform support for the flexible film 21 and the wafer.

[0068] In some embodiments, the first protrusion 122 is strip-shaped, and correspondingly, the first groove 132 is also strip-shaped and extends along the first direction X.

[0069] In some embodiments, a plurality of first protrusions 122 are arranged at equal intervals to simplify the manufacturing process of the adsorption body 11.

[0070] In some embodiments, please refer to Figure 2 Along the second direction Y, the size d1 of the first protrusion 122 is smaller than the size d2 of the first groove 132, so as to reduce the support area of ​​the first protrusion 122, thereby reducing the support area of ​​the adsorption body 11 on the wafer and reducing the risk of damage to the wafer during the adsorption process.

[0071] In some embodiments, along the second direction Y, the ratio of the size d1 of the first protrusion 122 to the size d2 of the first groove 132 is greater than 0 and less than or equal to 0.2, so as to ensure that the first protrusion 122 has a suitable size to support the wafer and reduce the risk of wafer damage.

[0072] In some embodiments, please refer to Figure 3 The adsorption hole 112 may include one or more first adsorption holes 113, the first adsorption holes 113 penetrating the bottom of the first groove 132.

[0073] It should be noted that the first adsorption hole 113 can communicate with the cavity in the rod 31 through the cavity inside the adsorption body 11.

[0074] In some embodiments, when the first adsorption hole 113 penetrates the bottom of the first groove 132, the orthogonal projection of at least one through hole 213 on the adsorption surface 111 can overlap with the first adsorption hole 113, thereby increasing the vacuuming speed of the through hole 213.

[0075] In some embodiments, the first adsorption hole 113 may also be offset from the through hole 213.

[0076] In some embodiments, please refer to Figure 1 The through hole 213 may include a first through hole 214. The orthographic projection of the first through hole 214 on the adsorption surface 111 may be located in the bottom of the first groove 132 to ensure that the first groove 132 and the first through hole 214 can be effectively connected.

[0077] In some embodiments, please refer to Figure 2 and Figure 3 The plurality of first grooves 132 may include intermediate grooves 134 and edge grooves 135. Along the second direction Y, the plurality of intermediate grooves 134 are located between two edge grooves 135. Along the first direction X, at least one edge groove 135 is smaller in size than the intermediate groove 134, so as to reduce the volume of the edge groove 135, which helps the edge groove 135 and the intermediate groove 134 to reach the target vacuum level in a similar time when the adsorption hole 112 is close to the intermediate groove 134.

[0078] In some embodiments, please refer to Figure 2 and Figure 3 The protrusion 121 also includes a second protrusion 123, which is arranged around a plurality of first protrusions 122. A first groove 132 is also provided between the second protrusion 123 and the first protrusions 122. In this way, the second protrusion 123 can support the edge of the flexible membrane 21, reducing the risk of deformation of the flexible membrane 21 during vacuum adsorption.

[0079] In some embodiments, please refer to Figure 2 and Figure 3The groove 131 further includes a second groove 133. Each first protrusion 122 includes a first end and a second end opposite to each other. The first end of each first protrusion 122 is connected to the second protrusion 123. A second groove 133 is provided between the second end of each of the plurality of first protrusions 122 and the second protrusion 123. The second groove 133 extends along the second direction Y and communicates with the plurality of first grooves 132 and the adsorption hole 112. Thus, the plurality of first grooves 132 are connected through the second groove 133 to ensure that the vacuum degree in the plurality of first grooves 132 tends to be the same during the vacuuming process. Furthermore, the first end of each first protrusion 122 is connected to the second protrusion 123, so that one end of the first groove 132 is closed, shortening the time for each first groove 132 to reach the target vacuum degree.

[0080] In some embodiments, please refer to Figure 2 and Figure 3 The adsorption hole 112 may include a second adsorption hole 114, which penetrates the bottom of the second groove 133. In this way, the second adsorption hole 114 evacuates the multiple first grooves 132 through the second groove 133, which helps to make the vacuum degree in the multiple first grooves 132 tend to be the same.

[0081] In some embodiments, the second adsorption hole 114 penetrates to the middle of the bottom of the second groove 133. This helps to reduce the time difference in reaching the target vacuum level between the multiple first grooves 132 on both sides of the adsorption hole 112.

[0082] In some embodiments, please refer to Figure 1 and Figure 3 The second groove 133 can be adjacent to the rod 31, so that the adsorption hole 112 is also adjacent to the rod 31, so as to realize the cavity communication between the adsorption hole 112 and the rod 31, simplifying the manufacturing process of the wafer adsorption device 100. In addition, the adsorption hole 112 can be vacuumed more quickly through the second groove 133 and multiple first grooves 132.

[0083] In some embodiments, please refer to Figure 1 and Figure 4 The through hole 213 may also include a second through hole 215. The orthographic projection of the second through hole 215 on the adsorption surface 111 may be located in the bottom of the second groove 133 to ensure that the second groove 133 and the second through hole 215 can be effectively connected.

[0084] In some embodiments, the orthogonal projection of the second through hole 215 on the adsorption surface 111 can overlap with the second adsorption hole 114, thereby increasing the vacuuming speed of the second through hole 215.

[0085] In some embodiments, the second through hole 215 may be offset from the second adsorption hole 114.

[0086] In summary, in some embodiments of the wafer adsorption device of this application, a flexible film is added to the adsorption surface of the adsorption body. The flexible film has through holes, and the through holes are connected to the adsorption holes that penetrate the adsorption surface. Thus, when the adsorption body grips the wafer, the adsorption body supports the wafer, and the through holes on the flexible film adsorb the wafer, allowing the flexible film to directly contact the wafer, thereby improving the problem of wafer scratches caused by direct contact between the adsorption body and the wafer.

[0087] The above description of the embodiments is only for the purpose of helping to understand the technical solutions and core ideas of this application; those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A wafer adsorption device, characterized in that, include: An adsorption body includes an adsorption surface and is provided with adsorption holes, the adsorption holes penetrating the adsorption surface; A flexible membrane is located on the adsorption surface and has through holes; wherein the through holes penetrate the flexible membrane along the thickness direction of the flexible membrane and are connected to the adsorption holes.

2. The wafer adsorption device according to claim 1, characterized in that, The flexible membrane includes an adhesive layer and an antistatic layer, with the adhesive layer located between the adsorption surface and the antistatic layer.

3. The wafer adsorption device according to claim 2, characterized in that, The thickness of the antistatic layer is 40 micrometers to 60 micrometers.

4. The wafer adsorption device according to claim 1, characterized in that, The thickness of the flexible membrane is 0.5 mm to 1.2 mm.

5. The wafer adsorption device according to claim 1, characterized in that, The adsorption surface is also provided with protrusions, and a groove is provided between two adjacent protrusions. The flexible membrane is located on the protrusions, and the adsorption pore is connected to the through hole through the groove.

6. The wafer adsorption device according to claim 5, characterized in that, The protrusion includes a plurality of first protrusions, and the groove includes a first groove. The plurality of first protrusions extend along a first direction and are arranged at intervals along a second direction. A first groove is provided between adjacent first protrusions. The first direction intersects the second direction.

7. The wafer adsorption device according to claim 6, characterized in that, Along the second direction, the size of the first protrusion is smaller than the size of the first groove.

8. The wafer adsorption device according to claim 6, characterized in that, The protrusion further includes a second protrusion, which is arranged around a plurality of the first protrusions, and the first groove is also provided between the second protrusion and the first protrusion; The groove further includes a second groove. Each of the first protrusions includes a first end and a second end opposite to each other. The first end of each of the first protrusions is connected to the second protrusion. The second groove is provided between the second end of each of the first protrusions and the second protrusion. The second groove extends along the second direction and communicates with the plurality of first grooves.

9. The wafer adsorption device according to claim 8, characterized in that, The adsorption hole penetrates the bottom of the second groove.

10. The wafer adsorption device according to any one of claims 1 to 9, characterized in that, The wafer adsorption device further includes a rod portion connected to the adsorption body, and the rod portion having an internal cavity that communicates with the adsorption orifice; and / or, The diameter of the adsorption pore is larger than the diameter of the through pore; and / or, The diameter of the through hole is 200 micrometers to 300 micrometers; and / or, The distribution density of the through holes is 15 per cm. 2 ~25 pieces / cm 2 .

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