Wafer cleaning basket, pickling process and wafer back process
By improving the design of the slot depth and rectangular hole size of the wafer cleaning basket, the problem of blackening at the wafer edge was solved, resulting in higher product aesthetics and quality, and ensuring the smooth progress of subsequent processes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GTA SEMICON CO LTD
- Filing Date
- 2022-10-27
- Publication Date
- 2026-05-29
AI Technical Summary
In the back-side pickling process of wafers, blackened stripe patterns are easily formed at the contact point between the wafer edge and the cleaning basket, which affects the product appearance and subsequent metal deposition operations, and reduces product quality.
An improved wafer cleaning basket is designed. By adjusting the slot depth and rectangular hole size, the contact area between the wafer edge and the basket is reduced, and the acid flow is made consistent to avoid uneven etching speed. The design adopts a structure in which the slot depth gradually decreases from the center to the edge.
This effectively avoids blackening at the wafer edges, improves the wafer's aesthetics, ensures product quality, and reduces the impact on subsequent metal deposition operations.
Smart Images
Figure CN115662927B_ABST
Abstract
Description
Technical Field
[0001] This specification relates to the field of semiconductor technology, specifically to a wafer cleaning basket, an acid washing process, and a wafer backside process. Background Technology
[0002] After the front-side devices are fabricated on the wafer, a thinning process is performed on the back side, for example, reducing the wafer thickness from 750µm to about 200µm. The thinned wafer then undergoes a back-side wet chemical treatment, followed by the deposition of metals such as Ti, Ni, and Ag. This effectively reduces the on-resistance and thermal effects of the manufactured chip, minimizing energy loss and ensuring chip reliability. Thinning is typically done using mechanical polishing. During polishing, a damage layer is formed on the back side of the wafer. Multiple wafers are then placed in a cleaning basket, which is then immersed in an acid bath for etching, removing a certain thickness from the back side of the wafer to remove the damage layer. However, due to the high viscosity of the etching acid, blackened stripe patterns can easily form at the junction of the wafer back side and the cleaning basket, affecting the appearance of the chip product and, in severe cases, impacting subsequent metal deposition processes and reducing product quality. Summary of the Invention
[0003] In view of this, the embodiments of this specification provide a wafer cleaning basket, an acid pickling process, and a wafer back-side process. The wafer cleaning basket can prevent the back side of the wafer from turning black during the acid pickling process, improve the aesthetics of the product, and ensure the quality of the wafer product.
[0004] The embodiments in this specification provide the following technical solutions:
[0005] A wafer cleaning basket is applicable to the acid washing process of the grinding damage layer on the back side of a wafer. The wafer cleaning basket includes two carrier plates arranged facing each other and two fixing plates arranged facing each other. The carrier plates and the fixing plates are vertically connected in sequence at the opening of the wafer cleaning basket to form a frame structure.
[0006] The two carrier plates are provided with symmetrical loading areas, each loading area including at least two retaining strips perpendicular to the fixing plate. A plurality of rectangular holes for the passage of pickling solution are provided between the retaining strips. The inner walls of the retaining strips are provided with slots for placing wafers. The slots and the rectangular holes are configured as follows:
[0007] When the opening of the wafer cleaning basket is placed vertically upward, the groove depth near the horizontal center line of the loading area is less than the groove depth away from the horizontal center line, the size of the lower rectangular hole is not less than the size of the upper rectangular hole, and the upper and lower edges of the rectangular hole are formed by the edges of the clips.
[0008] In the above solution, by changing the shape and structure of the wafer cleaning basket, instead of using a slot structure with the same depth, the depth of the slots near the center and bottom of the cleaning basket is reduced, and the depth of the slots near the center of the cleaning basket is smaller than that at the bottom. When the cleaning basket is placed in the pickling tank with its opening vertically upward, the contact area between the edge near the horizontal center line of the wafer and the slots becomes smaller. At the same time, a rectangular hole with a larger diameter than the top area is opened at the bottom of the side wall of the cleaning basket, so that the flow rate of acid at the edge of the wafer is as similar as possible to the flow rate in other areas of the wafer. This avoids the phenomenon of surface blackening at the edge of the wafer due to different etching rates, making the wafer more aesthetically pleasing, reducing the impact on subsequent metal deposition operations, and ensuring the quality of the wafer products.
[0009] This specification also provides an embodiment in which the number of slots is 2N+1. When the pickling process is performed, the wafer is placed in the slot numbered 2N, where N is a natural number.
[0010] This specification also provides an embodiment where the card strip includes a first card strip, a second card strip, and a third card strip from top to bottom, wherein the second card strip is close to the horizontal center line;
[0011] The depth of the groove on the inner wall of the second card strip is 0.4 to 1 cm;
[0012] The groove depth of the inner wall of the third card strip is 0.5 to 1.2 cm.
[0013] This specification also provides an embodiment in which the groove depth of the inner wall of the second card strip is 0.4 to 0.5 cm;
[0014] The groove depth of the inner wall of the third card strip is 0.5 to 0.8 cm.
[0015] This specification also provides an embodiment in which the groove wall of the card slot extends along a direction parallel to the fixing plate to an adjacent card strip to form a reinforcing strip, the reinforcing strip constituting the left and right edges of the rectangular hole and being configured as follows:
[0016] The number of reinforcing strips farther away from the opening is no greater than the number of reinforcing strips closer to the opening.
[0017] This specification also provides an embodiment in which the reinforcing strip is not provided between the two card strips furthest from the opening.
[0018] This specification also provides an embodiment in which the height of the reinforcing strip along the direction parallel to the fixing plate is the same as the depth of the slot on any adjacent side.
[0019] This specification also provides an embodiment in which the wafer cleaning basket further includes a movable handle that is movably connected to the fixing plate.
[0020] This specification also provides an acid etching process for removing the grinding damage layer on the back side of a wafer. Using a wafer cleaning basket as described in any of the above embodiments, the wafer cleaning basket containing multiple wafers is placed into an acid etching machine for etching, thereby removing the mechanically ground damage layer.
[0021] This specification also provides an embodiment of a wafer back-side process, including the following steps:
[0022] Choose a protective film that is acid-resistant and does not easily leave residue;
[0023] Apply the protective film to the front side of the wafer;
[0024] Mechanically grind the back side of the wafer to a preset thickness;
[0025] The pickling process described in any of the above methods is used to remove the damage layer formed by mechanical grinding on the back side of the wafer.
[0026] Remove the protective film from the front side of the wafer;
[0027] Ti, Ni, or Ag metal is deposited on the back of the wafer to form ohmic contacts, which serve as leads during chip packaging.
[0028] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above-mentioned technical solutions adopted in the embodiments of this specification include at least the following: When performing the pickling process, the wafer cleaning basket provided by the present invention, with its improved structure, can effectively reduce the contact area between the middle and bottom edges of the wafer and the wafer cleaning basket when the wafer is placed vertically, ensuring that the acid flow rate is the same at all points on the back of the wafer, thereby ensuring that the etching rate is the same at all points on the edge of the wafer, avoiding the phenomenon of surface blackening at the edge, improving the aesthetics of the wafer, and ensuring the quality of the wafer product. Attached Figure Description
[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0030] Figure 1 This is a three-dimensional schematic diagram of an existing wafer cleaning basket;
[0031] Figure 2 This is a front view schematic diagram of the loading area of an existing wafer cleaning basket;
[0032] Figure 3 This is a schematic diagram of the color difference on the surface of a wafer after acid washing using an existing wafer cleaning basket.
[0033] Figure 4 This is a front view schematic diagram of the loading area of the wafer cleaning basket in the first embodiment;
[0034] Figure 5 This is a front view schematic diagram of the loading area of the wafer cleaning basket in the second embodiment;
[0035] Figure 6 This is a front view schematic diagram of the loading area of the wafer cleaning basket in the third embodiment;
[0036] Figure 7 yes Figure 4 Schematic diagram of the cross section at point A-A';
[0037] Figure 8 yes Figure 4 Cross-sectional view at point B-B';
[0038] Figure 9 yes Figure 4 Schematic diagram of the cross section at C-C';
[0039] Figure 10 This is a schematic diagram showing that the wafer surface has no color difference after acid washing using the wafer cleaning basket provided by this invention;
[0040] Figure 11 This is a flowchart of a wafer back-side process;
[0041] Among them, 10, carrier plate, 11, loading area, 13, card slot, 14, rectangular hole, 15, card strip, 16, first card strip, 17, second card strip, 18, third card strip, 19, reinforcing strip, 20, fixing plate, 50, movable handle, 60, support foot, 100, wafer. Detailed Implementation
[0042] The embodiments of this application will now be described in detail with reference to the accompanying drawings.
[0043] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0044] It should be noted that the following description covers various aspects of embodiments within the scope of the appended claims. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.
[0045] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0046] It should be understood that "the connection between component A and component B" means that component A is directly connected to component B, or that component A is indirectly connected to component B through other components. The directional terms such as "upper," "lower," "inner," "outer," and "side" described in the exemplary embodiments of this specification are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the exemplary embodiments of this specification.
[0047] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.
[0048] Typically, after the front-side devices are fabricated on the wafer, a back-side process is used to thin the wafer to a predetermined thickness, for example, reducing the wafer thickness from 750µm to around 200µm. A common back-side process involves wet chemical treatment followed by deposition of metals such as Ti, Ni, and Ag. This process effectively reduces the chip's on-resistance and thermal effects, thereby reducing energy consumption during chip operation and ensuring chip reliability.
[0049] Thinning operations typically employ mechanical polishing, which uses a diamond-tipped blade while simultaneously spraying water to polish the back side of the wafer to a specified thickness, such as approximately 200µm. During mechanical polishing, damage is created on the polished surface (i.e., the back side of the wafer). This damaged layer can be removed using chemical etching. For example, using… Figure 1 and Figure 2The wafer cleaning basket shown is used in an acid etching machine to etch a certain thickness on the back of the wafer to remove the damage layer caused by mechanical grinding.
[0050] The wafer cleaning basket has multiple slots 13, in which wafers 100 are placed. The slots 13 are located on the inner wall of the basket's retaining strips 15. Under normal circumstances, the basket is placed with its opening facing vertically, and its bottom is equipped with support legs 60. Carrier plates 10 are located on opposite sides of the basket, and each carrier plate 10 has a loading area 11 for loading the wafers 100. Multiple retaining strips 15 are distributed within the loading area 11. Multiple slots 13 for supporting the wafers 100 are arranged parallel to each other on the inner wall of each retaining strip 15. Each retaining strip 15 can be divided into a first retaining strip 16 near the opening, a second retaining strip 17 near the center of the basket, and a third retaining strip 18 near the bottom of the basket. Multiple reinforcing strips 19 are provided between adjacent retaining strips 15, and the gaps between horizontally adjacent reinforcing strips 19 form rectangular holes 14, allowing acid to enter the cleaning basket during etching. However, due to the large contact area between the wafer 100 and the slot 13, and the high viscosity of the acid, the size of the hole (i.e., the rectangular hole 14) on the side of the basket for acid to pass through is limited. This obstructs the liquid flow at the junction of the back of the wafer 100 and the cleaning basket, resulting in blackened stripe patterns at this location after etching. Figure 3 As shown, this affects the appearance of the chip product, and in severe cases, it can affect subsequent metal deposition operations and reduce product quality.
[0051] To address the aforementioned problems, this invention proposes a novel wafer cleaning basket based on structural improvements to existing wafer cleaning baskets. Its basic structure can be referenced as follows: Figure 1 The wafer cleaning basket shown is formed by connecting two carrier plates and two fixing plates around the perimeter. Its interior forms an inner cavity for accommodating multiple wafers for etching processes. The basket opens vertically upwards, and multiple groove structures (i.e., slots) are provided from the opening to the bottom of the basket for placing and fixing the wafers.
[0052] When a wafer is placed inside a basket, the edge of the wafer near the horizontal center line of the basket is closer to the inner wall of the basket. If the depth of the slots is kept uniform, the edge of the wafer near the horizontal center line will enter the slot more, thus affecting the flow of etching acid at that location. Similarly, the slots near the bottom of the basket support the wafer from the side and below, and the edge of the wafer at these locations will also enter the slot more than the edge of the wafer near the opening, which also obstructs the flow of etching acid at that location. These locations where the wafer is fixed will form the blackened striped pattern described above. Therefore, the inventors set the slots on the inner wall of the wafer cleaning basket to different depths. Since the wafer edge has the most contact with the slot at the horizontal center line in the prior art, the depth of the slot at this location is set to be smaller relative to that location. At the same time, the depth of the slot near the bottom of the wafer cleaning basket is appropriately reduced. When the wafer is placed vertically in the wafer cleaning basket, it is guided from the slot near the opening to slide into the inside of the basket and fixed by the sliding grooves on the side (near the horizontal center line of the basket) and the lower side (near the bottom of the basket), forming a "four-point fixing" structure. At the same time, in order to ensure that the slots used for fixing can form a sufficient acid flow rate, the rectangular holes near these areas are larger than the rectangular holes at the opening, thereby effectively solving the problem of wafer back blackening and affecting product quality during etching.
[0053] The technical solutions provided by the various embodiments of this application are described below with reference to the accompanying drawings.
[0054] A wafer cleaning basket is provided for acid cleaning processes of the damaged layer on the back side of a wafer. The wafer cleaning basket includes two opposing carrier plates 10 and two opposing fixing plates 20. The carrier plates 10 and fixing plates 20 are vertically connected sequentially at the opening of the wafer cleaning basket to form a frame structure. (Reference) Figure 1 As shown. Two carrier plates 10 are provided with symmetrical loading areas 11. Each loading area 11 includes at least two retaining strips 15 perpendicular to the fixing plate 20. Several rectangular holes 14 for the passage of pickling solution are provided between the retaining strips 15. The inner wall of each retaining strip 15 is provided with a slot 13 for placing the wafer 100. The slot 13 is configured such that when the opening of the wafer cleaning basket is placed vertically upwards (i.e., when using the wafer cleaning basket for the pickling and etching process), the slot depth of the slot 13 near the horizontal center line of the loading area 11 is less than the slot depth of the slot 13 away from the horizontal center line. Figure 4 , Figure 7 , Figure 8 and Figure 9 As shown, the second locking strip 17, closest to the horizontal center line, has the smallest depth, the first locking strip 16, closest to the opening, has the largest depth, and the third locking strip 18, closest to the bottom, has a depth between the two; and the rectangular hole 14 is configured such that the size of the lower rectangular hole 14 is not smaller than the size of the upper rectangular hole 14, and the upper and lower edges of the rectangular hole 14 are formed by the edges of the locking strips 15, as shown. Figures 4 to 6 As shown, the size of the rectangular hole 14 near the bottom is larger than the size of the rectangular hole 14 near the opening, and the rectangular hole 14 is formed by the edges of the locking strips 15. For example, the upper and lower edges of the rectangular hole 14 located between the first locking strip 16 and the second locking strip 17 are formed by the lower edge of the first locking strip 16 and the upper edge of the second locking strip 17, respectively. It should be noted that in some embodiments, such as Figure 4 and Figure 5 As shown, the rectangular hole 14 between the first card strip 16 and the second card strip 17 has the same size as the rectangular hole 14 between the second card strip 17 and the third card strip 18; in other embodiments, such as Figure 6 As shown, the size of the rectangular hole 14 between the second card strip 17 and the third card strip 18 is larger than the size of the rectangular hole 14 between the first card strip 16 and the second card strip 17.
[0055] In the above solution, by resetting the depth of the slots 13 that contact the edge of the wafer 100 at various points on the inner wall of the cleaning basket, and simultaneously adjusting the size of the rectangular holes 14, the morphology of the existing cleaning basket is optimized based on its basic structure. During the etching process, this reduces the obstruction of the etching solution by its sidewalls and internal structure, thereby preventing blackening on the back side of the wafer, making the wafer more aesthetically pleasing, reducing the impact on subsequent metal deposition operations, and ensuring wafer product quality. Figure 10 As shown.
[0056] It should be noted that the wafer cleaning basket with the above structure can be obtained by machining existing wafer cleaning baskets, or by directly using molding processes such as injection molding.
[0057] In some implementations, the number of slots 13 is 2N+1. When the pickling process is performed, the wafer 100 is placed in the slot 13 numbered 2N, where N is a natural number.
[0058] For example, such as Figure 4 and Figure 5 As shown, there are 25 slots 13, of which 12 are used to place the etched and acid-washed wafers 100, that is, they are placed in the 2nd, 4th, 6th... 24th slots.
[0059] In the above scheme, by increasing the distance between wafers 100, the flow of acid is made smoother, which can better suppress the phenomenon of blackening at the wafer edges.
[0060] It should be noted that in some other implementations, the number of card slots 13 is 2M+1, and the wafer 100 can also be placed in the card slot 13 with the serial number 2M+1, where M is a non-negative integer.
[0061] It should be noted that in some other implementations, the spacing between the wafers 100 in the multiple slots 13 can also be set to two or more slots.
[0062] In some implementation schemes, such as Figure 4 , Figure 7 , Figure 8 , Figure 9 As shown, the card strip 15 includes, from top to bottom: a first card strip 16 near the opening of the wafer cleaning basket, a second card strip 17 near the horizontal center line of the wafer cleaning basket, and a third card strip 18 near the bottom of the wafer cleaning basket; and there can be multiple first card strips 16, second card strips 17, and third card strips 18, for example... Figure 4 The first locking strip 16 consists of two strips; the groove 13 on the inner wall of the second locking strip 17 has a depth of 0.4–1 cm; and the groove 13 on the inner wall of the third locking strip 18 has a depth of 0.5–1.2 cm. Preferably, the groove 13 on the inner wall of the second locking strip 17 has a depth of 0.4–0.5 cm; and the groove 13 on the inner wall of the third locking strip 18 has a depth of 0.5–0.8 cm.
[0063] In some implementation schemes, such as Figure 4 and Figure 5 As shown, reinforcing strips 19 are also provided between the clips 15 of the wafer cleaning basket. These reinforcing strips 19 are formed by extending from the groove wall of the slot 13 along a direction parallel to the fixing plate 20 to the adjacent clip 15. Therefore, the groove walls of the reinforcing strips 19 and slot 13 are connected in a straight line, facilitating sliding guidance during the placement and removal of the wafer 100. Furthermore, the reinforcing strips 19 form the left and right edges of the rectangular hole 14 and are configured such that the number of reinforcing strips 19 farther from the opening is no greater than the number of reinforcing strips 19 closer to the opening, for example... Figure 4 The number of reinforcing strips 19 between the second first clip 16 and the second clip 17 shown from top to bottom is the same as the number of reinforcing strips 19 between the second clip 17 and the third clip 18. It should be noted that in some embodiments, such as... Figure 6 As shown, the number of reinforcing strips 19 between the second strip 17 and the third strip 18 can also be less than the number of reinforcing strips 19 between the first strip 16 and the second strip 17.
[0064] In some other embodiments, no reinforcing strip 19 is provided between the two card strips 15 furthest from the opening. For example, no reinforcing strip 19 is provided between the second card strip 17 and the third card strip 18.
[0065] It should be noted that in the embodiment with the reinforcing strip 19 described above, the height of the reinforcing strip 19 is adapted to the depth of the slot 13. Specifically, the height of the reinforcing strip 19 along the direction parallel to the fixing plate 20 is the same as the depth of the slot 13 on any adjacent side. Preferably, the height of the reinforcing strip 19 along the direction parallel to the fixing plate 20 is the same as the depth of the slot 13 on the side closer to the opening of the wafer cleaning basket.
[0066] In some embodiments, the wafer cleaning basket also includes a movable handle 50 that connects to the retaining plate 20. When loading or unloading the wafer 100, the movable handle 50 can be rotated to avoid the wafer 100.
[0067] Based on the same inventive concept, this specification also provides an acid cleaning process for removing the grinding damage layer on the back of a wafer. This acid cleaning process uses the wafer cleaning basket described in any of the above solutions. During acid cleaning and etching, the wafer cleaning basket containing multiple wafers is placed into the acid bath machine for etching to remove the mechanical grinding damage layer.
[0068] The beneficial effects of the pickling process for removing the grinding damage layer on the back side of the wafer can be seen in the effect of the wafer cleaning basket in the foregoing embodiments, and will not be repeated here.
[0069] Based on the same inventive concept, embodiments of this specification also provide a wafer backside process, such as... Figure 11 As shown, it includes the following steps:
[0070] Step S1: Select a protective film that is acid-resistant and does not easily leave residue;
[0071] Step S2: Apply the protective film to the front side of the wafer;
[0072] Step S3: Mechanically grind the back of the crystal to a preset thickness;
[0073] Step S4: Use the pickling process described in the above embodiment to remove the damage layer formed by mechanical grinding on the back of the wafer;
[0074] Step S5: Remove the protective film from the front side of the wafer;
[0075] Step S6: Deposit Ti, Ni or Ag metal on the back side of the wafer to form ohmic contacts, which will serve as leads during chip packaging.
[0076] The beneficial effects of the above-described wafer backside process can be seen in the effect of the wafer cleaning basket in the foregoing embodiments, and will not be repeated here.
[0077] In this specification, the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the method embodiments described later are relatively simple in description since they correspond to the system, and relevant parts can be referred to the descriptions in the system embodiments.
[0078] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A wafer cleaning basket, suitable for the acid washing process of the damaged layer on the back side of a wafer, characterized in that, The wafer cleaning basket includes two opposing carrier plates and two opposing fixing plates. The carrier plates and the fixing plates are vertically connected in sequence at the opening of the wafer cleaning basket to form a frame structure. The two carrier plates are provided with symmetrical loading areas, each loading area including at least two retaining strips perpendicular to the fixing plate. A plurality of rectangular holes for the passage of pickling solution are provided between the retaining strips. The inner walls of the retaining strips are provided with slots for placing wafers. The slots and the rectangular holes are configured as follows: When the opening of the wafer cleaning basket is placed vertically upward, the groove depth near the horizontal center line of the loading area is less than the groove depth away from the horizontal center line, the size of the lower rectangular hole is not less than the size of the upper rectangular hole, and the upper and lower edges of the rectangular hole are formed by the edge of the clip. The number of slots is 2N+1. When the pickling process is performed, the wafer is placed in the slot numbered 2N, where N is a natural number. The card strip includes a first card strip, a second card strip, and a third card strip from top to bottom, wherein the second card strip is close to the horizontal center line; The depth of the groove on the inner wall of the second card strip is 0.4~1cm; The groove depth of the inner wall of the third card strip is 0.5~1.2cm.
2. The wafer cleaning basket according to claim 1, characterized in that, The depth of the groove on the inner wall of the second card strip is 0.4~0.5cm; The groove depth of the inner wall of the third card strip is 0.5~0.8cm.
3. The wafer cleaning basket according to claim 1, characterized in that, The groove wall of the slot extends parallel to the fixing plate to the adjacent locking strip to form a reinforcing strip, which constitutes the left and right edges of the rectangular hole and is configured as follows: The number of reinforcing strips farther away from the opening is no greater than the number of reinforcing strips closer to the opening.
4. The wafer cleaning basket according to claim 3, characterized in that, The reinforcing strip is not provided between the two card strips furthest from the opening.
5. The wafer cleaning basket according to claim 3, characterized in that, The height of the reinforcing strip along the direction parallel to the fixing plate is the same as the depth of the slot on any adjacent side.
6. The wafer cleaning basket according to claim 1, characterized in that, The wafer cleaning basket also includes a movable handle that is movably connected to the fixing plate.
7. An acid pickling process for removing the grinding damage layer on the back side of a wafer, characterized in that, Using the wafer cleaning basket as described in any one of claims 1 to 6, the wafer cleaning basket containing multiple wafers is placed into an acid bath machine for etching to remove the damaged layer from mechanical grinding.
8. A wafer backside process, characterized in that, Includes the following steps: Choose a protective film that is acid-resistant and does not easily leave residue; Apply the protective film to the front side of the wafer; Mechanically grind the back side of the wafer to a preset thickness; The pickling process described in claim 7 is used to remove the damage layer formed by mechanical grinding on the back side of the wafer; Remove the protective film from the front side of the wafer; Ti, Ni, or Ag metal is deposited on the back of the wafer to form ohmic contacts, which serve as leads during chip packaging.