A method for wafer backside thinning and wafer structure
By forming a protective adhesive at the wafer edge, stress during the thinning process is absorbed, solving the problem of wafer breakage, improving wafer yield, and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGXIN MEMORY TECH INC
- Filing Date
- 2021-10-27
- Publication Date
- 2026-07-21
AI Technical Summary
During the chemical mechanical polishing process to thin wafers, the wafers are prone to breakage, which affects the yield and cost of subsequent processing.
A protective adhesive is formed at the edge of the first side of the wafer. The adhesive covers the sharp corners and absorbs stress during the thinning process, thereby reducing the probability of cracking.
By absorbing stress with protective adhesive, the probability of wafer breakage during the thinning process is reduced, wafer yield is improved, and the cost of subsequent processing is reduced.
Smart Images
Figure CN113990740B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the semiconductor field, and in particular to a method for thinning the back side of a wafer and a wafer structure. Background Technology
[0002] A wafer is a silicon wafer used to manufacture silicon semiconductor integrated circuits. Because its shape is generally set as circular, it is called a wafer. Various circuit element structures can be processed on silicon wafers, which are called integrated circuit products with specific electrical functions. In wafer processing technology, wafers usually need to be thinned before subsequent packaging, testing and other processes can be carried out. Commonly used thinning processes are divided into three types: mechanical polishing, chemical etching and chemical mechanical planarization.
[0003] Mechanical grinding typically involves placing the wafer on a chuck and thinning it through two steps: rough grinding followed by fine grinding. Chemical etching typically involves placing the wafer in a chemical etching solution and controlling the etching time or other process parameters to achieve a specific thickness reduction. Chemical mechanical planarization typically involves fixing the wafer, applying a chemical slurry, and then using a polishing pad to evenly distribute the slurry on the wafer, thereby achieving wafer thinning.
[0004] However, wafer breakage can occur during the current process of thinning wafers using chemical mechanical polishing. Summary of the Invention
[0005] This application provides a method for thinning the back side of a wafer, which at least helps to reduce the probability of wafer breakage during mechanical grinding and thinning.
[0006] According to some embodiments of this application, this application provides a method for thinning the back side of a wafer, comprising: providing a wafer having opposing first and second sides, and the wafer having a central region and an edge region, the edge region surrounding the central region; forming a protective adhesive in the edge region of the first side, the protective adhesive further covering a portion of the side adjacent to the first side, and the top surface of the protective adhesive being higher than the first side; performing a thinning process on the second side of the wafer along a direction from the second side to the first side, and during the thinning process, also thinning a portion of the thickness of the protective adhesive.
[0007] In some embodiments, the protective adhesive also covers the central area of the portion of the first surface adjacent to the edge area.
[0008] In some embodiments, during the process of forming the protective adhesive, a continuous protective adhesive is formed around the edge region.
[0009] In some embodiments, during the process of forming the protective adhesive, a plurality of the protective adhesives are formed around the edge region and spaced apart.
[0010] In some embodiments, the first surface has a radial direction, and the width of the protective adhesive along the radial direction is less than or equal to 1.5 mm.
[0011] In some embodiments, in a direction perpendicular to the first surface of the central region, the distance between the bottom surface of the protective adhesive away from the first surface and the first surface of the central region is 30 μm to 200 μm.
[0012] In some embodiments, the distance between the top surface of the protective adhesive and the first surface of the central region is 50 μm to 250 μm in a direction perpendicular to the first surface of the central region.
[0013] In some embodiments, the material of the protective adhesive includes thermosetting phenolic resin, epoxy resin, or a combination of thermosetting phenolic resin and epoxy resin.
[0014] In some embodiments, the process of forming the protective adhesive includes: forming an initial protective adhesive in the edge region of the first surface and a portion of the side surface adjacent to the first surface; and performing a thermosetting treatment on the initial protective adhesive to form the protective adhesive.
[0015] In some embodiments, the method of forming the initial protective adhesive includes: providing a support stage and a nozzle device; placing the second side of the wafer on the support stage, and using the nozzle device to spray a protective adhesive material onto the first side of the edge region, wherein during the spraying process, the support stage drives the wafer to rotate around the central axis of the wafer to form the initial protective adhesive.
[0016] In some embodiments, the thermosetting temperature range of the protective adhesive is 90°C to 180°C.
[0017] In some embodiments, the edge region includes an adjacent beveled region and a flat region, the flat region being located between the beveled region and the center region, and the wafer thickness of the beveled region gradually decreasing in the direction from the center region to the beveled region; before forming the protective adhesive, the process further includes: cutting a portion of the beveled region in the direction from the first surface to the second surface to form a first cut surface adjacent to the first surface of the flat region and a second cut surface adjacent to the first cut surface; in the process step of forming the protective adhesive, the protective adhesive covers the first cut surface, the second cut surface, and a portion of the first surface of the flat region.
[0018] In some embodiments, the angle between the first surface of the flat region and the first tangential surface ranges from 90° to 170°.
[0019] In some embodiments, the distance between the second cut surface and the first surface of the flat region is 30 μm to 200 μm in a direction perpendicular to the first surface of the central region.
[0020] A wafer structure, characterized in that it comprises: a wafer structure formed by the wafer backside thinning method described above.
[0021] The technical solution provided in this application has at least the following advantages: by forming a protective adhesive in the edge region of the first side of the wafer, the protective adhesive also covers the side adjacent to the first side, and the top surface of the protective adhesive is higher than the first side, the second side of the wafer is thinned in the direction from the second side to the first side. During the thinning process, the protective adhesive absorbs part of the stress on the sharp corner, thereby reducing the probability of wafer breakage during the thinning process, thereby improving the wafer yield and providing a foundation for subsequent integrated circuits. Attached Figure Description
[0022] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.
[0023] Figures 1 to 6 This application provides a schematic diagram of the structure corresponding to each step of a method for thinning the back side of a wafer in an embodiment of the present application.
[0024] Figures 7 to 11 This is a schematic diagram of the structure corresponding to each step of a method for thinning the back side of a wafer, provided in another embodiment of this application. Detailed Implementation
[0025] As can be seen from the background technology, wafer edge cracking can occur during the wafer thinning process.
[0026] This application provides a method for thinning the back side of a wafer by forming a protective adhesive in the edge region of the first side of the wafer. The protective adhesive absorbs the stress during the wafer thinning process, thereby reducing the probability of wafer breakage.
[0027] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.
[0028] Figures 1 to 6 The following is a structural side view of each step in a method for thinning the back side of a wafer, provided in an embodiment of this application.
[0029] The embodiments of this application will be described in more detail below with reference to the accompanying drawings.
[0030] refer to Figure 1 A wafer 100 is provided, the wafer 100 having a first side 101 and a second side 102 opposite to each other, and the wafer 100 having a central region 103 and an edge region 104, the edge region 104 surrounding the central region 103.
[0031] In some embodiments, the first surface 101 is one side used for manufacturing semiconductor devices, and the second surface 102 is the opposite side of the first surface 101. That is, subsequent processes such as etching, deposition and electroplating are performed on the wafer 100 on the first surface 101 to manufacture the required semiconductor devices on the first surface 101.
[0032] In some embodiments, the edge region 104 includes an adjacent beveled region 105 and a flat region 106, the flat region 106 being located between the beveled region 105 and the center region 103, and the thickness of the wafer 100 of the beveled region 105 gradually decreasing in the direction from the center region 103 to the beveled region 105.
[0033] In some embodiments, the wafer 100 is drum-shaped. Therefore, in the direction from the center region 103 to the oblique region 105, the thickness of the wafer 100 in the oblique region 105 gradually decreases. It can be understood that the shape of the wafer 100 is related to the manufacturing process. That is, when the seed crystal is placed in the crucible and rotated at a constant speed and pulled upward, the molten silicon grows along the seed crystal into a silicon ingot. The silicon ingot is cut into silicon wafers, and the silicon wafers are then processed by corresponding chamfering and polishing processes to become the wafer 100.
[0034] It should be noted that the central area 103, edge area 104, oblique edge area 105, and flat area 106 are merely divisions of different regions of wafer 100, and not limitations on wafer 100.
[0035] refer to Figure 2 Before forming the protective adhesive, the process further includes: cutting the beveled area 105 of a certain thickness in the direction from the first surface 101 to the second surface 102 to form a first cut surface 107 adjacent to the first surface 101 of the flat area 106 and a second cut surface 108 adjacent to the first cut surface 107; in the process of forming the protective adhesive, the protective adhesive covers the first cut surface 107, the second cut surface 108 and part of the first surface 101 of the flat area 106.
[0036] In some embodiments, the method for processing the edge of the wafer 100 can be by mechanical grinding, in which the angle between the first surface 101 and the first cut surface 107 is controlled by controlling the angle of the wafer 100 or the angle of the grinding tool during grinding.
[0037] In some embodiments, the angle between the first surface 101 and the first tangential surface 107 of the flat region 106 ranges from 90° to 170°.
[0038] By controlling the angle of the cutting process, the flatness of the surface of the beveled area 105 can be improved. It is understood that when the included angle α between the first surface 101 and the first cutting surface 107 of the flat area 106 is 90°, the surface flatness of the beveled area 105 after cutting is the highest. The included angle α between the first surface 101 and the first cutting surface 107 of the flat area 106 can also be other angles, such as 150° or 170°.
[0039] In the direction perpendicular to the first surface 101 of the central region 103, the distance between the second tangential surface 108 and the first surface 101 of the flat region 106 is 30 μm to 200 μm. (Reference) Figure 2 The distance between the second cut surface 108 and the first surface 101 of the flat area 106 is the height of the first cut surface 107. It can be understood that the height of the first cut surface 107 can be set according to the thickness of the wafer 100 required after thinning the wafer 100.
[0040] When the distance between the second cut surface 108 and the first surface 101 of the flat region 106 is less than 30 μm, that is, in the direction perpendicular to the surface of the wafer 100, the thickness of the remaining wafer 100 after thinning is less than 30 μm. When the thickness of the remaining wafer 100 is less than 30 μm, the wafer 100 may break during the subsequent packaging process, making it difficult to package the wafer 100 or reducing the packaging yield. When the distance between the second cut surface 108 and the first surface 101 of the flat region 106 is greater than 200 μm, that is, in the direction perpendicular to the surface of the wafer 100, the thickness of the remaining wafer 100 after thinning is relatively thick. This may increase the packaging cost of the subsequent packaging of the wafer 100, and the excessive thickness of the remaining wafer 100 is also not conducive to the subsequent stacking or TSV process.
[0041] refer to Figures 3 to 4 A protective adhesive 110 is formed in the edge region 104 of the first surface 101. The protective adhesive 110 also covers the side surface adjacent to the first surface 101, and the top surface of the protective adhesive 110 is higher than the first surface 101.
[0042] It is understandable that after the edge trimming process, sharp corners will be formed between the first surface 101 and the first cut surface 107, and between the first cut surface 107 and the second cut surface 108 of the flat area 106. When the sharp corners are subjected to stress, the stress is greater due to the small area of the sharp corners, so wafer 100 is more likely to break at the sharp corners. By covering the sharp corners with protective adhesive 110, when the sharp corners are subjected to stress, some of the force will be transferred to the protective adhesive 110, thereby reducing the stress on the sharp corners and thus reducing the probability of wafer 100 breakage during the wafer 100 thinning process.
[0043] For details, please refer to Figure 3 The process steps for forming the protective adhesive 110 include: forming an initial protective adhesive in the edge region 104 of the first surface 101 and the side surface adjacent to the first surface 101; and performing a heat curing treatment on the initial protective adhesive to form the protective adhesive 110.
[0044] Thermosetting treatment can improve the mechanical properties of the protective adhesive 110, such as hardness, wear resistance, and strength, thereby better protecting the wafer 100.
[0045] The material of the protective adhesive 110 includes thermosetting phenolic resin, epoxy resin, or a combination of thermosetting phenolic resin and epoxy resin.
[0046] Thermosetting phenolic resin, epoxy resin, or a combination of thermosetting phenolic resin and epoxy resin have good elasticity and good adhesion. Good elasticity can absorb the stress caused by vibration during the thinning of wafer 100, and good adhesion can help fix the protective adhesive 110 to wafer 100. In addition, the internal stress generated during curing is small, thereby avoiding the protective adhesive 110 itself from affecting wafer 100.
[0047] Taking the material of protective adhesive 110 as thermosetting phenolic resin as an example, thermosetting phenolic resin is a substance that can be compatible with a variety of organic and inorganic fillers, and can provide a certain mechanical strength after cross-linking. Furthermore, thermosetting phenolic resin is an amorphous substance, and its shape can be adjusted according to requirements.
[0048] In some embodiments, the thermosetting temperature range of the protective adhesive 110 is 90°C to 180°C.
[0049] In other embodiments, other methods can be used to cure the initial protective adhesive, as long as the cured protective adhesive 110 has a certain strength.
[0050] In some embodiments, the method of forming an initial protective adhesive includes: providing a support stage (not shown) and a nozzle device (not shown); placing the second side 102 of the wafer 100 on the support stage, and using the nozzle device to spray a protective adhesive material onto the first side 101 of the edge region 104, and during the spraying process, the support stage drives the wafer 100 to rotate around the central axis of the wafer 100 to form an initial protective adhesive.
[0051] It is understandable that by rotating the wafer 100 with the support stage, the volume of the initial protective adhesive can be controlled by controlling the speed of spraying the protective adhesive material with the nozzle device and the number of rotations of the support stage. Furthermore, the initial protective adhesive formed by rotating the wafer 100 with the support stage and spraying the protective adhesive material with the nozzle device has a relatively uniform thickness at each point in the direction perpendicular to the first surface 101.
[0052] In some embodiments, the support stage can rotate at a constant speed, and the rotation speed and number of rotations can be adjusted as needed. The nozzle device can spray protective adhesive material at a constant speed, and the spraying speed and total amount of spraying can be controlled. This application does not limit the support stage and the nozzle device, as long as they can achieve the purpose of driving the wafer 100 to rotate and spraying protective adhesive material.
[0053] In some embodiments, the protective adhesive 110 also covers the central region 103 of the portion of the first surface 101 adjacent to the edge region 104.
[0054] It is understandable that a sharp corner is formed between the first surface 101 and the first cut surface 107. The sharp corner is covered by the protective adhesive 110. When the sharp corner is subjected to force, some of the force will be transferred to the protective adhesive 110, thereby reducing the stress on the sharp corner and thus reducing the probability of wafer 100 breakage during the wafer 100 thinning process.
[0055] In some embodiments, during the process of forming the protective adhesive 110, a continuous protective adhesive 110 is formed around the edge region 104. That is, by controlling the rotation of the wafer 100 and coordinating the spraying of the protective adhesive material, a continuous protective adhesive 110 is formed around the edge region 104. By forming a continuous protective adhesive 110 around the edge region 104, the sharp corners formed between the first surface 101 and the first cut surface 107 and between the first cut surface 107 and the second cut surface 108 are completely covered, thereby protecting both of these sharp corners and reducing the stress on the sharp corner portions, thereby reducing the probability of wafer 100 breakage during the wafer 100 thinning process.
[0056] In other embodiments, during the process of forming the protective adhesive 110, a plurality of protective adhesives 110 are formed around the edge region 104 and spaced apart. That is, by controlling the rotation of the wafer 100 and spraying the protective adhesive material, a plurality of protective adhesives 110 are formed around the edge region 104 but spaced apart from each other. The spaced protective adhesives 110 can also protect the sharp corners formed between the first surface 101 and the first cut surface 107 and the sharp corners formed between the first cut surface 107 and the second cut surface 108. By reducing the stress on the sharp corners, the probability of wafer 100 breakage during wafer 100 thinning is reduced.
[0057] The first surface 101 has a radial direction, and the width of the protective adhesive 110 along the radial direction is less than or equal to 1.5 mm.
[0058] Specifically, the radial direction is the direction extending from the geometric center of the first surface 101 to the edge of the first surface 101. Taking the first surface 101 as a circle as an example, the radial direction is the direction from the center of the circle to the edge of the circle.
[0059] The width of the protective adhesive 110 is less than or equal to 1.5 mm, such as 1.4 mm, 1.3 mm or 1.2 mm. By limiting the range of the protective adhesive 110, the range protected by the protective adhesive 110 is limited, thereby reducing the impact of the protective adhesive 110 on the performance of the subsequently formed semiconductor structure. When the width of the protective adhesive 110 in the radial direction is greater than 1.5 mm, it may cause the area covered by the protective adhesive 110 to be too large, thereby affecting the performance of the subsequently formed semiconductor structure.
[0060] In some embodiments, the width of the protective adhesive 110 in the radial direction along the first surface 101 may also be related to the width of the second cut surface 108 formed after the edge trimming process. When the width of the protective adhesive 110 is greater than the width of the second cut surface 108, the protective adhesive 110 covers the sharp corner formed between the first surface 101 and the first cut surface 107, thereby reducing the stress on the sharp corner portion and thus reducing the probability of wafer 100 breakage during wafer 100 thinning process.
[0061] In some embodiments, in a direction perpendicular to the first surface 101 of the central region 103, the distance between the bottom surface of the protective adhesive 110 away from the first surface 101 and the first surface 101 of the central region 103 is 30 μm to 200 μm. (Reference) Figure 3 The distance between the bottom surface of the protective adhesive 110 away from the first surface 101 and the first surface 101 of the central area 103 is the height of the first cut surface 107 in the direction perpendicular to the first surface 101. It can be understood that the height of the first cut surface 107 can be set according to the thickness of the wafer 100 required after thinning the wafer 100.
[0062] When the distance between the protective adhesive 110 and the bottom surface of the first surface 101 of the central region 103 is less than 30 μm, that is, in the direction perpendicular to the surface of the wafer 100, the thickness of the remaining wafer 100 after thinning is less than 30 μm. When the thickness of the remaining wafer 100 is less than 30 μm, the wafer 100 may break during the subsequent packaging process, making it difficult to package the wafer 100 or reducing the packaging yield. When the distance between the protective adhesive 110 and the bottom surface of the first surface 101 of the central region 103 is greater than 200 μm, that is, in the direction perpendicular to the surface of the wafer 100, the thickness of the remaining wafer 100 after thinning is relatively thick, which may increase the packaging cost of the subsequent packaging of the wafer 100. Moreover, the excessive thickness of the remaining wafer 100 is also not conducive to the subsequent stacking or TSV process.
[0063] In some embodiments, the distance between the top surface of the protective adhesive 110 and the first surface 101 of the central region 103 in a direction perpendicular to the first surface 101 of the central region 103 is 50 μm to 250 μm.
[0064] When the distance between the top surface of the protective colloid 110 and the first surface 101 of the central region 103 is less than 50 μm, the distance between the sharp corner formed between the first surface 101 and the first cut surface 107 and the protective colloid 110 in the direction perpendicular to the first surface 101 is less than 50 μm. The protective colloid 110 has limited stress absorption capacity and cannot effectively protect the sharp corner formed between the first surface 101 and the first cut surface 107. When the subsequent thinning of the wafer 100 causes vibration, the sharp corner formed between the first surface 101 and the first cut surface 107 is still prone to cracking. When the distance between the top surface of the protective colloid 110 and the first surface 101 of the central region 103 is greater than 250 μm, the protective colloid 110 on the top surface of the beveled region 105 is prone to cracking, which will weaken the stress absorption function of the protective colloid 110 and increase the production cost.
[0065] refer to Figure 4 In some embodiments, some of the unwanted protective adhesive 110 can also be removed.
[0066] It should be noted that during the formation of the protective adhesive 110, since the protective adhesive 110 is not cured, it has a certain degree of fluidity. Therefore, the protective adhesive 110 will also cover the second side 102 of the wafer 100. However, the part of the protective adhesive 110 covering the second side 102 can be removed.
[0067] It is understandable that the unwanted protective adhesive 110 is the protective adhesive 110 between the second cut surface 108 and the second surface 102. In some embodiments, the wafer 100 between the second cut surface 108 and the second surface 102 will be removed before the wafer 100 is thinned. Since the material properties of the protective adhesive 110 have a certain mechanical strength, the unwanted protective adhesive 110 is removed first in order to speed up the thinning rate of the wafer 100.
[0068] In some embodiments, the material of the protective adhesive 110 is a thermosetting phenolic resin, and the material for removing the protective adhesive 110 can be an organic solvent such as acetone or alcohol. By placing the second side 102 of the wafer 100 on a support stage, an organic solvent such as acetone or alcohol is sprayed onto the first side 101 of the edge area 104 using a nozzle device to remove some of the unwanted protective adhesive 110.
[0069] It is understandable that the process of removing part of the protective adhesive 110 can be that the wafer 100 is placed on a carrier stage, and the wafer 100 is rotated by rotating the carrier stage, thereby removing part of the unwanted protective adhesive 110 by spraying organic solvent.
[0070] refer to Figure 5 The first surface 101 of the wafer 100 is placed on the support stage, and the wafer 100 is thinned by the second surface 102 facing the first surface 101.
[0071] The methods for thinning wafer 100 can include mechanical grinding, chemical etching, or chemical mechanical planarization. Taking mechanical grinding as an example, the second surface 102 of wafer 100 is first rough ground and then fine ground. Rough grinding can reduce the grinding time to achieve the purpose of rapidly thinning wafer 100, while fine grinding can reduce the roughness after rough grinding to meet the surface roughness requirements of wafer 100.
[0072] During the grinding process, the wafer 100 will inevitably vibrate. The vibration of the wafer 100 will cause the wafer 100 to be under stress. The protective adhesive 110 can absorb some of the stress, thereby reducing the stress on the sharp corners formed between the first surface 101 and the first cut surface 107 and the sharp corners formed between the first cut surface 107 and the second cut surface 108. By reducing the stress on the sharp corners, the probability of the wafer 100 breaking during the wafer thinning process is reduced.
[0073] refer to Figure 6 The wafer 100 is thinned to the required thickness. After the wafer 100 is thinned, the heat dissipation efficiency of the wafer 100 can be improved. As the chip structure becomes more and more complex, the integration level becomes higher and higher, and the number of transistors increases, the thinner wafer 100 is more conducive to the heat dissipation from the wafer 100. After the wafer 100 is thinned, the packaging area of the subsequent chip can also be reduced, and the internal stress of the chip can be reduced.
[0074] It is understandable that when the distance between the second cut surface 108 and the first surface 101 of the flat region 106 in the direction perpendicular to the first surface 101 of the central region 103 is 30μm to 200μm, for example, 200μm, after thinning, part of the wafer 100 between the first surface 101 and the second cut surface 108 is removed. Therefore, the thickness of the wafer 100 formed after thinning can be less than 200μm. It is understandable that the thickness of the wafer 100 formed after thinning can be reduced according to the requirements of the corresponding wafer 100 thickness.
[0075] This application forms a protective adhesive 110 in the edge region 104 of the first surface 101 of the wafer 100. The protective adhesive 110 covers a portion of the side surface adjacent to the first surface 101. The wafer 100 is thinned in the direction from the second surface 102 to the first surface 101. The protective adhesive 110 absorbs part of the stress on the wafer 100 during the thinning process, thereby protecting the wafer 100 and reducing the probability of wafer 100 breakage during the thinning process.
[0076] Another embodiment of this application provides a method for thinning the back side of a wafer. This method is generally the same as the aforementioned embodiment, with the main difference being that the wafer is not diced in this embodiment. The following will describe the method for thinning the back side of a wafer provided in another embodiment of this application with reference to the accompanying drawings. It should be noted that the same or corresponding parts as those in the aforementioned embodiments can be referred to the corresponding descriptions in the aforementioned embodiments, which will not be repeated below.
[0077] refer to Figure 7 A wafer 200 is provided, the wafer 200 having a first side 201 and a second side 202 opposite to each other, and the wafer 200 having a central region 203 and an edge region 204, the edge region 204 surrounding the central region 203.
[0078] In some embodiments, the edge region 204 includes an adjacent beveled region 205 and a flat region 206, the flat region 206 being located between the beveled region 205 and the center region 203, and the thickness of the wafer 200 of the beveled region 205 gradually decreasing in the direction from the center region 203 to the beveled region 205.
[0079] refer to Figure 8 A protective adhesive 210 is formed in the edge region 204 of the first surface 201. The protective adhesive 210 also covers the side surface adjacent to the first surface 201, and the top surface of the protective adhesive 210 is higher than the first surface 201.
[0080] refer to Figure 9To remove part of the protective adhesive 210, the first side 201 of the wafer 200 can be placed on the carrier stage. The wafer 200 is rotated by rotating the carrier stage, and the unwanted part of the protective adhesive 210 is removed by applying an organic solvent.
[0081] refer to Figure 10 The first side 201 of the wafer 200 is placed on the support stage, and the wafer 200 is thinned by the second side 202 facing the first side 201.
[0082] refer to Figure 11 When wafer 200 is thinned to the required thickness, it is understandable that during the thinning process, sharp corners will form between the arc-shaped edge of the edge region 204 of wafer 200 and the second surface 202. These sharp corners are prone to breakage. Protective adhesive 210 is used to protect these sharp corners. During the thinning process, the protective adhesive 210 absorbs the stress on some of the sharp corners, thereby improving the stress resistance of wafer 200 and thus reducing the probability of wafer 200 breakage during the thinning process.
[0083] In this embodiment, a protective adhesive 210 is formed in the edge region 204 of the first surface 201 of the wafer 200. The protective adhesive 210 covers a portion of the side surface adjacent to the first surface 201. The wafer 200 is thinned in the direction from the second surface 202 to the first surface 201. The protective adhesive 210 absorbs some of the stress on the wafer 200 during the thinning process, thereby protecting the wafer 200 and reducing the probability of wafer 200 breakage during the thinning process.
[0084] This application also provides a wafer structure, including a wafer structure formed by some or all of the steps of the wafer backside thinning method described above.
[0085] Those skilled in the art will understand that the above-described embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of this application. Any person skilled in the art can make their own modifications and alterations without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.
Claims
1. A method for thinning the back side of a wafer, characterized in that, include: A wafer is provided having opposing first and second faces, and the wafer having a central region and an edge region, the edge region surrounding the central region; A protective adhesive is formed in the edge area of the first surface, the protective adhesive also covers a portion of the side surface adjacent to the first surface, and the top surface of the protective adhesive is higher than the first surface; The second surface of the wafer is thinned along the direction from the second surface to the first surface, and the protective adhesive of a certain thickness is also thinned during the thinning process.
2. The method for thinning the back side of a wafer according to claim 1, characterized in that, The protective adhesive also covers the central area of the portion of the first surface adjacent to the edge area.
3. The method for thinning the back side of a wafer according to claim 1, characterized in that, In the process of forming the protective adhesive, a continuous protective adhesive is formed around the edge area.
4. The method for thinning the back side of a wafer according to claim 1, characterized in that, In the process of forming the protective adhesive, a plurality of the protective adhesives are formed around the edge area and spaced apart.
5. The method for thinning the back side of a wafer according to claim 1, characterized in that, The first surface has a radial direction, and along the radial direction, the width of the protective adhesive is less than or equal to 1.5 mm.
6. The method for thinning the back side of a wafer according to claim 1, characterized in that, In a direction perpendicular to the first surface of the central region, the distance between the bottom surface of the protective adhesive away from the first surface and the first surface of the central region is 30μm to 200μm.
7. The method for thinning the back side of a wafer according to claim 1, characterized in that, In the direction perpendicular to the first surface of the central region, the distance between the top surface of the protective adhesive and the first surface of the central region is 50 μm to 250 μm.
8. The method for thinning the back side of a wafer according to claim 1, characterized in that, The protective adhesive is made of thermosetting phenolic resin, epoxy resin, or a combination of thermosetting phenolic resin and epoxy resin.
9. The method for thinning the back side of a wafer according to claim 1, characterized in that, The process steps for forming the protective adhesive include: forming an initial protective adhesive in the edge area of the first surface and the portion of the side surface adjacent to the first surface; and subjecting the initial protective adhesive to a heat-curing treatment to form the protective adhesive.
10. The method for thinning the back side of a wafer according to claim 9, characterized in that, The method for forming the initial protective adhesive includes: Provide a support platform and nozzle assembly; The second side of the wafer is placed on the support platform, and a protective adhesive material is sprayed onto the first side of the edge region using the nozzle device. During the spraying process, the support platform drives the wafer to rotate around the central axis of the wafer to form the initial protective adhesive.
11. The method for thinning the back side of a wafer according to claim 9, characterized in that, The thermosetting temperature range of the protective adhesive is 90℃~180℃.
12. The method for thinning the back side of a wafer according to claim 1, characterized in that, The edge region includes an adjacent beveled region and a flat region. The flat region is located between the beveled region and the center region, and the thickness of the wafer in the beveled region gradually decreases in the direction from the center region to the beveled region. Before forming the protective adhesive, the process further includes: cutting a portion of the beveled region in the direction from the first surface to the second surface to form a first cut surface adjacent to the first surface of the flat region and a second cut surface adjacent to the first cut surface. In the process step of forming the protective adhesive, the protective adhesive covers the first cut surface, the second cut surface, and a portion of the first surface of the flat region.
13. The method for thinning the back side of a wafer according to claim 12, characterized in that, The angle between the first surface and the first tangential surface of the flat region is in the range of 90° to 170°.
14. The method for thinning the back side of a wafer according to claim 12, characterized in that, In the direction perpendicular to the first surface of the central region, the distance between the second sectional surface and the first surface of the flat region is 30 μm to 200 μm.