Wafer thinning method

Abstract

The invention discloses a wafer thinning method, which comprises the following steps: providing a wafer and a bonding piece with a hollow structure, pasting the front surface of the bonding piece on the second surface of the wafer, and enclosing to form a glue accommodating cavity; the glue containing cavity is filled with glue and solidified to form a plastic supporting body, and the first surface of the wafer is ground and thinned; and dissolving and cleaning the glue condensate on the wafer, and taking down the bonding piece. Compared with the prior art, the bonding piece is pasted on the wafer, and then the bonding piece is filled with the glue and solidified to form the plastic supporting body, so that the plastic supporting body and the bonding piece are connected with the wafer together to serve as a thickening supporting body of the wafer, the wafer thinning difficulty is reduced, the plastic supporting body can be directly dissolved after the wafer is thinned, and the wafer thinning difficulty is reduced. Therefore, no adhesive residue is left on the wafer, and the bonding member can be used repeatedly.

Description

Technical Field

[0001] This invention relates to semiconductor fabrication, and more particularly to a wafer thinning method. Background Technology

[0002] Currently, high-density packaging requires reducing wafer thickness to below 100µm. However, when thinning to below 100µm, wafer warpage becomes very significant. There are two main technological approaches to achieve ultra-thin wafer reduction. One approach only thins the middle of the wafer, leaving the edges thin, which can reduce the wafer to below 50µm. Then, the outer ring of the wafer is cut off. This thinning process is relatively complex and often requires high-precision grinding equipment. The other approach uses a temporary carrier to thicken the wafer. After thickening, the wafer can be thinned, and then the carrier is debonded. After debonding, the temporary carrier is essentially unusable, leading to higher costs.

[0003] Therefore, there is an urgent need for a wafer thinning method that can solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a wafer thinning method, in which bonding components are attached to the surface of the wafer, and then glue is filled into the bonding components and cured, so that the plastic support and bonding components are connected to the wafer as a thickening support for the wafer, reducing the difficulty of wafer thinning. After the wafer is thinned, the cured glue can be directly dissolved and cleaned, so that no glue residue is left on the wafer, and the bonding components can be reused.

[0005] To achieve the above objectives, the present invention provides a wafer thinning method, comprising: Step 1, providing a wafer and a bonding component, wherein the wafer has opposing first and second surfaces, the bonding component has opposing front and back sides, the bonding component includes an edge support portion, and the edge support portion is provided with at least one hollow structure penetrating the front and back sides; the front side of the bonding component is adhered to the second surface of the wafer such that the edge support portion is correspondingly adhered to the edge position of the second surface of the wafer, thereby closing the opening of the hollow structure on the front side of the bonding component, and the hollow structure forms an adhesive receiving cavity with an opening on the back side of the bonding component; Step 2, filling the adhesive receiving cavity with adhesive, and the adhesive curing to form a plastic support body; Step 3, supporting the wafer through the bonding component and / or the plastic support body during the grinding process to grind and thin the first surface of the wafer; Step 4, dissolving and cleaning the cured adhesive on the wafer, and removing the bonding component, wherein the cured adhesive includes the plastic support body. Preferably, the bonding member is a bonding ring, and the hollow structure is the central hole of the bonding ring. This design results in the bonding member consisting of an annular edge support portion.

[0006] Preferably, in step 2, the adhesive cavity is filled with adhesive, and after the adhesive cures, a plastic support is formed. The plastic support is positioned away from the back side of the wafer and at the same height as the back side of the bonding component, forming a grinding and positioning surface parallel to the first surface of the wafer. In step 3, after the wafer is adsorbed and fixed by the grinding and positioning surface, the first surface of the wafer is ground and thinned.

[0007] Preferably, in step 3, after the wafer is fixed by clamping the bonding member, the first surface of the wafer is ground and thinned.

[0008] More preferably, in step 2, the grinding positioning surface is further processed into a flat mirror surface. At this time, the grinding positioning surface is a flat mirror surface, which can effectively improve the accuracy of wafer thinning and optimize the warpage performance after wafer thinning.

[0009] Preferably, between steps 3 and 4, there is an additional step: attaching a protective film to the thinned surface of the wafer.

[0010] Preferably, in step 1, the step of attaching the front side of the bonding component to the second surface of the wafer includes: applying an adhesive of a first thickness to the second surface of the wafer to form an adhesive layer, and then attaching and fixing the bonding component to the second surface of the wafer through the adhesive layer. In step 2, after the adhesive filling the adhesive cavity cures, it bonds integrally with the cured adhesive layer, and the cured adhesive layer also includes the cured adhesive layer. Specifically, the first thickness is 1-50 μm.

[0011] Preferably, the main materials of the adhesive are ketones, ethers, or esters, which are easily soluble and do not leave residues after washing. Specifically, the adhesive also contains silicon oxides and nitrides, which can increase the hardness of the adhesive and adjust its coefficient of thermal expansion.

[0012] Preferably, the bonding component is a metal component, semiconductor component, ceramic component, glass component, or polymer component, which has a certain hardness and is corrosion resistant.

[0013] Preferably, the thickness of the edge support portion is 100~2000μm, so that the thickness of the plastic support body is 100~2000μm, which can increase the thickness and strength of the wafer, and enable the support structure composed of the bonding component and the plastic support body to effectively support the wafer.

[0014] Preferably, the outer diameter of the edge support portion is greater than or equal to the outer diameter of the wafer, and the inner diameter of the edge support portion is smaller than the outer diameter of the wafer. Alternatively, the outer diameter of the edge support portion can be smaller than the outer diameter of the wafer, but the distance between them must be kept within a preset distance so that the edge support portion can effectively support the edge of the wafer.

[0015] The edge support portion is annular and has an inner frame therein. The hollow structure is formed on the inner frame and / or between the inner frame and the edge support portion. The front of the inner frame is flush with the front of the edge support portion, and the back of the inner frame is lower than or flush with the back of the edge support portion.

[0016] Preferably, the ratio of the projected area of ​​the hollow structure on the front side to the projected area of ​​the bonding component on the front side is greater than or equal to 20%, ensuring that the contact area between the bonding component and the wafer is within a preset range, so that the bonding component can be easily separated from the wafer by dissolving the plastic support.

[0017] Compared with existing technologies, this invention involves bonding a bonding element to the second surface of the wafer, then filling the hollow structure of the bonding element with adhesive. After curing, this forms a soluble plastic support, which, once solidified, tightly bonds to the wafer, acting as a thickening support for the wafer. This reduces the difficulty of wafer thinning, allowing for wafer thinning using ordinary grinding machines, and ensuring that the warpage during wafer thinning remains within acceptable limits. On one hand, the edge support portion of the bonding element acts as an adhesive filling mold, simultaneously supporting the wafer from the edge to ensure its back surface is flat. The plastic support within the bonding element bonds the bonding element to the wafer, effectively enhancing the tightness of the connection between the bonding element and the wafer, and between the plastic support and the wafer, ensuring stress balance during wafer thinning through grinding. On the other hand, the present invention uses a plastic support formed by curing ordinary glue as the main body for wafer thickening. After the wafer is thinned, since the vast majority of the plastic support (especially the part corresponding to most of the wafer surface) is exposed, the plastic support can be directly dissolved over a large area. After dissolution and cleaning, no glue residue is left on the wafer, and the bonding components can be reused repeatedly, resulting in low cost. Attached Figure Description

[0018] Figure 1 This is a flowchart of the wafer thinning method in Embodiment 1 of the present invention.

[0019] Figure 2 This is a flowchart of the wafer thinning method in Embodiment 2 of the present invention.

[0020] Figure 3 This is a top view of the bonding component in Embodiment 3 of the present invention.

[0021] Figure 4This is a side cross-sectional view of the bonding component in Embodiment 3 of the present invention.

[0022] Figure 5 This is a top view of the bonding component in Embodiment 4 of the present invention.

[0023] Figure label: Wafer 10, thinned wafer 10a; bonding components 20, 20a, 20b, adhesive layer 31, plastic support 30; protective film 40, retaining ring 41; edge support 21, internal frame 22, 22a, hollow structure 23. Detailed Implementation

[0024] To illustrate the technical content, structural features, objectives, and effects of the present invention in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0025] Example 1, Reference Figure 1 The present invention discloses a wafer thinning method, including steps S1 to S4.

[0026] S1, a wafer 10 and a bonding member 20 are provided. The wafer 10 has a first surface to be polished and a second surface opposite to the first surface and supporting it during polishing. The bonding member 20 has opposing front and back sides. The bonding member 20 includes an edge support portion, and at least one hollow structure penetrating the front and back sides is provided in the edge support portion. The front side of the bonding member 20 is pasted onto the second surface of the wafer 10, and the edge support portion is pasted to correspond to the edge area of ​​the second surface of the wafer 10, so as to close the opening of the hollow structure on the front side of the bonding member 20, thereby forming an adhesive receiving cavity with an opening on the back side of the bonding member.

[0027] The bonding component 20 is a bonding ring, and the hollow structure is the central hole of the bonding ring 20. That is, the bonding component consists of an edge support portion, which is annular with a hollow inner hole. This allows for the formation of an adhesive cavity between the bonding component 20 and the wafer 10 when the bonding component 20 is attached to the wafer 10, preventing adhesive leakage. This design increases the contact area between the cured adhesive and the solvent in subsequent steps, making cleaning easier. It also minimizes the contact area between the bonding component 20 and the wafer 10, reducing the likelihood of cured adhesive residue remaining on the bonding component 20.

[0028] Wherein, the outer diameter of the edge support portion is greater than or equal to the outer diameter of the wafer 10, and the inner diameter of the edge support portion is smaller than the outer diameter of the wafer 10. Of course, the outer diameter of the edge support portion can also be smaller than the outer diameter of the wafer 10, but the distance between the edge support portion and the outer diameter of the wafer 10 must be kept within a preset distance so that the bonding member 20 can effectively support the edge of the wafer 10.

[0029] Specifically, step S1 includes steps S11 and S12.

[0030] refer to Figure 1 S11, apply a first thickness of adhesive to the second surface of the wafer 10 to form an adhesive bonding layer 31. This adhesive bonding layer 31 can be a bonding layer pattern with a width slightly wider than the solid portion of the bonding member 20, or it can be an adhesive layer that completely covers the second surface of the wafer 10. S12, attach the bonding member 20 to the second surface of the wafer 10 through the adhesive bonding layer 31.

[0031] It should be understood that, in some embodiments, when bonding the bonding element 20, efforts are made to ensure that the wafer 1 and the edge support have a high degree of concentricity.

[0032] The first thickness is 1-50 μm. The bonding component 20 is a metal component, semiconductor component (e.g., silicon component), polymer component (e.g., resin component), ceramic component, or glass component, etc., and has a certain hardness and corrosion resistance. The thickness of the edge support portion is 100~2000 μm, so that the thickened support component composed of the bonding component 20 and the plastic support 30 can effectively support the wafer 10 and prevent the wafer 10 from warping during grinding and thinning.

[0033] The difference between the outer and inner diameters of the edge support portion is 50~10000μm, ensuring that the bonding member 20 effectively supports the wafer 10 while preventing the relative bonding area between the bonding member 20 and the wafer 10 from becoming too high, facilitating the cleaning of the cured adhesive. Specifically, the ratio of the projected area of ​​the hollow structure on the front side of the bonding member 20 to the projected area of ​​the bonding member 20 on the front side is greater than or equal to 20%.

[0034] S2, the adhesive cavity formed by the back of the bonding member 20 and the wafer 10 is filled with adhesive, and the adhesive cures to form a plastic support 30.

[0035] More preferably, in step S2, after forming the plastic support 30, the plastic support 30 is made to be at the same height as the back side of the bonding member 20 away from the back side of the wafer 10, and forms a grinding positioning surface parallel to the first surface of the wafer 10 with the back side of the bonding member 20.

[0036] Specifically, step S2 includes steps S21 and S22. (See reference) Figure 1 S21, the adhesive cavity formed by the back sides of the bonding member 20 and the wafer 10 is filled with adhesive. S22, the adhesive is cured to form a plastic support 30, which is connected to the bonding member 20 to form a thickened support for the wafer 10.

[0037] The adhesive used in this application is a ketone, ether, or ester-based adhesive. The main materials of the adhesive are ketones, ethers, or esters, and it also contains silicon, Al oxides, and nitrides, which can increase the hardness of the adhesive and adjust its coefficient of thermal expansion. The adhesive used to bond the bonding member 20 to the second surface of the wafer 10 has the same main components as the adhesive filling the adhesive cavity; they are the same type of adhesive. Preferably, the adhesive used to bond the bonding member 20 has a lower fluidity than the adhesive filling the adhesive cavity.

[0038] The plastic support 30 formed by the cured adhesive filling the adhesive cavity and the cured adhesive layer 31 are integrated into one unit.

[0039] The grinding positioning surface is processed into a flat mirror surface, which effectively improves the thinning accuracy of the wafer 10 and facilitates the adsorption and positioning of the wafer 10 during grinding and thinning. In step S22, after the glue is filled into the glue receiving cavity and cured, the back side of the plastic support 30 is smoothed or polished with a scraper so that the back side of the bonding member 20 and the back side of the plastic support 30 form a grinding positioning surface parallel to the first surface of the wafer 10, and this grinding positioning surface is a flat mirror surface.

[0040] S3, the wafer 10 is positioned by adsorption using the grinding positioning surface, and the first surface of the wafer 10 to be ground is ground and thinned to obtain a thinned wafer 10a, the thickness of which is a preset thickness. In this embodiment, the preset thickness is less than 100μm.

[0041] Of course, unlike this, when grinding and thinning the wafer 10, the wafer 10 can also be positioned by clamping and fixing the bonding member 20.

[0042] S4, dissolve and clean the cured adhesive on the wafer 10a, and remove the bonding member 20. The cured adhesive includes the cured plastic support 30 and the adhesive bonding layer 31.

[0043] In step S4, the thinned wafer 10a is placed in a solvent, so that the cured plastic support 30 and adhesive layer 31 are reacted and dissolved. The solvent is the same as the adhesive solution in steps S1 and S2, such as pure water, organic solvent or acid / alkali solvent, which can be selected according to the material of the adhesive.

[0044] refer to Figure 2 Unlike Example 1, in Example 2, between step S3 and step S4, there is also step S3a: attaching a protective film 40 to the polished and thinned surface of the wafer 10a after polishing and thinning.

[0045] Specifically, a vacuum laminator can be used to attach the protective film 40 to the polished and thinned surface of the wafer 10a. In particular, a fixing ring 41 with an inner diameter larger than the outer diameter of the wafer 10a is used to attach the protective film 40 to the polished and thinned surface of the wafer 10a.

[0046] The protective film 40 can prevent the wafer 10a from breaking during subsequent cutting processes, facilitate the positioning of the wafer 10a after cutting, and also support and fix the wafer 10a during the cleaning of the wafer 10a in step S4.

[0047] refer to Figure 3 and Figure 4 In embodiment 3, the bonding member 20a includes an edge support portion 21 and an inner frame 22. The edge support portion 21 is annular, and the inner frame 22 is disposed inside the edge support portion 21. In this embodiment, the hollow structure 23 is partially formed on the inner frame 22 and partially formed between the inner frame 22 and the edge support portion 21. Of course, the hollow structure can also be formed on the inner frame 22 or between the inner frame 22 and the edge support portion 21.

[0048] The internal frame 22 makes the bonding member 20a stronger and can serve as a strength support rib in the plastic support 30 in step S2, so that the thickened support composed of the final plastic support 30 and bonding member 20a has high strength and stable structure, and can better support the wafer 10.

[0049] refer to Figure 4 The front of the inner frame 22 is flush with the front of the edge support 21, and the back of the inner frame 22 is lower than the back of the edge support 21, so that the back of the inner frame 22 is recessed in the edge support 21, or the back of the inner frame 22 is flush with the back of the edge support 21.

[0050] The back side of the inner frame 22 is lower than the back side of the edge support 21, so that the back side of the inner frame 22 is recessed in the edge support 21. This design has two advantages: First, after the glue is filled into the glue cavity in step S2 and cured to form the plastic support 30, the back side of the plastic support 30 can be polished to form a flat mirror surface, which facilitates the adsorption and positioning of the wafer 10 in step S3. It also prevents damage to the bonding member 20a when processing the flat mirror surface. Second, this design also connects the glue in multiple hollow structures into a whole, and the cured plastic support 30 is also connected into a whole, further improving the bonding strength between the plastic support 30 and the bonding member 20a, thereby further enhancing the support of the plastic support 30 and the bonding member 20a for the wafer 10.

[0051] The internal frame 22 is composed of several interlaced strips, with the width of the strips preferably between 50 and 1000 μm. Specifically, the internal frame 22 is in the shape of a grid, but the structure of the internal frame 22 is not limited to this and can also be mesh-like, etc.

[0052] Of course, the internal frame 22 can also be composed of a plate with several through holes, which form a hollow structure.

[0053] The ratio of the projected area of ​​the hollow structure on the front side of the bonding member 20a to the projected area of ​​the bonding member 20a on the front side is greater than or equal to 20%.

[0054] refer to Figure 5 Unlike embodiment 3, in embodiment 4, the inner frame 22a of the bonding member 20b consists of an inner ring spaced apart from the edge support portion 21, and a connecting strip connecting the inner ring and the edge support portion 21.

[0055] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the scope of the present invention are still within the scope of the present invention.

Claims

1. A wafer thinning method, characterized by: The application relates to a method for thinning a wafer, comprising the following steps: step 1, providing a wafer and a bonding piece, the wafer having opposite first and second surfaces, the bonding piece having opposite front and back surfaces, the bonding piece comprising an edge support part, and at least one hollow structure being arranged in the edge support part and penetrating the front and back surfaces; the front surface of the bonding piece is pasted on the second surface of the wafer, and the edge support part is pasted at a position corresponding to the edge of the second surface of the wafer; the second surface is used to grind and thin the first surface of the wafer; step 2, filling the hollow structure with glue; step 3, grinding and thinning the first surface of the wafer; and step 4, dissolving and cleaning the glue solidification on the wafer, and removing the bonding piece. The bonding piece is a bonding ring, and the hollow structure is a central hole of the bonding ring. In step 2, the glue filling cavity is filled with glue, and the glue solidification forms a plastic support after the glue is solidified; the plastic support is at the same height as the back surface of the bonding piece and forms a grinding positioning surface with the back surface of the bonding piece, which is parallel to the first surface of the wafer; in step 3, the wafer is adsorbed and fixed through the grinding positioning surface, and then the first surface of the wafer is ground and thinned.

2. The wafer thinning method of claim 1, wherein: In step 3, the wafer is fixed by clamping the bonding piece, and then the first surface of the wafer is ground and thinned.

3. The wafer thinning method of claim 1, wherein: In step 2, the grinding positioning surface is processed into a flat mirror surface after the bonding piece is filled with glue and solidified. Between step 3 and step 4, a step of pasting a protective film on the ground and thinned surface of the wafer is further included. In step 1, the step of pasting the front surface of the bonding piece on the second surface of the wafer comprises the following steps: coating the second surface of the wafer with glue of a first thickness to form a glue pasting layer, and pasting and fixing the bonding piece on the second surface of the wafer through the glue pasting layer; in step 2, the glue filling cavity is filled with glue, and the glue solidification is integrated with the solidification of the glue pasting layer after the glue is solidified; the glue solidification further comprises the solidification of the glue pasting layer.

4. The wafer thinning method of claim 3, wherein: The main material of the glue is ketone, ether or ester material, and the glue further comprises silicon, Al oxide and nitride.

5. The wafer thinning method of claim 1, wherein: The bonding piece is a metal piece, a semiconductor piece, a ceramic piece, a glass piece or a polymer piece.

6. The wafer thinning method of claim 1, wherein: The thickness of the edge support part is 100-2000 mu m.

7. The wafer thinning method of claim 1, wherein: The outer diameter of the edge support part is greater than or equal to the outer diameter of the wafer, and the inner diameter of the edge support part is smaller than the outer diameter of the wafer.

8. The wafer thinning method of claim 1, wherein: The edge support part is annular and internally provided with an internal frame, the hollow structure is formed on the internal frame and / or between the internal frame and the edge support part, the front surface of the internal frame is flush with the front surface of the edge support part, and the back surface of the internal frame is lower than the back surface of the edge support part or flush with the back surface of the edge support part.

9. The wafer thinning method of claim 1, wherein: The projection area of the hollow structure on the front surface is greater than or equal to 20% of the projection area of the bonding piece on the front surface.

10. The wafer thinning method of claim 1, wherein: ​ 11. The wafer thinning method of claim 1, wherein: ​ 12. The wafer thinning method of claim 1, wherein: ​

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