Substrate thinning method

Abstract

The invention provides a thinning method of a substrate. By improving the protective film on the substrate, the top surface, located on the edge of the substrate, of the protective film is not lower than the top surface, located on the inner periphery of the substrate, of the protective film, so that when the substrate is placed on a grinding table, the edge part of the protective film can be attached to the table top, and a gap is prevented from being generated between the edge of the protective film and the table top; according to the technical scheme, grinding chips generated in the grinding process are effectively prevented from entering and making contact with the top surface of the protective film, so that in light source irradiation before film uncovering, the edge part of the protective film can be fully irradiated without being shielded by the grinding chips, and it is ensured that the protective film can be smoothly uncovered when the film is uncovered.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a substrate thinning method. Background Art

[0002] With the continuous development of semiconductor technology, based on the requirements for the electrical performance of devices, more and more products need to use thinning processes to reduce the thickness of the substrate during their manufacturing process so that the formed devices can achieve the expected electrical parameters. For example, in the preparation process of IGBT chips, backside grinding and backside metallization are crucial steps. Backside grinding can increase the flexibility of the chip, reduce the thermal impedance of the chip, and reduce the chip size. Backside metallization is conducive to achieving better heat dissipation and conductive effects.

[0003] Before the thinning process is performed, a film is usually applied to the front of the substrate to protect the front of the substrate, and then the back of the substrate is ground and thinned, and then the film is torn off, and the rest of the processing is continued. However, during the film tearing process, the protective film is often difficult to separate from the substrate, and even the substrate is brought into the roller of the film tearing equipment with the peeled protective film and is broken into pieces. Summary of the invention

[0004] The object of the present invention is to provide a method for thinning a substrate, and to solve the problem that a protective film is difficult to separate from a substrate during a film peeling process by optimizing a film sticking method.

[0005] In order to solve the above technical problems, the present invention provides a method for thinning a substrate, comprising: attaching a protective film on the first surface of the substrate, the top surface of the protective film located in the edge area of ​​the substrate is not lower than the top surface of the protective film located in the inner area of ​​the substrate; placing the substrate on a grinding table with its first surface facing the grinding table, the edge of the protective film is attached to the table surface of the grinding table, and performing a grinding process on the second surface of the substrate to thin the thickness of the substrate; and irradiating the protective film with a specific light source to reduce the viscosity of the protective film on the substrate, and then removing the protective film.

[0006] Optionally, the method of attaching a protective film on the first surface of a substrate includes: forming a dielectric layer on the first surface of the substrate, the dielectric layer covering a chip area on the substrate and also covering an edge area of ​​the substrate and having an edge ring; attaching a protective film on the first surface of the substrate, the edge of the protective film being attached to the edge ring of the dielectric layer, so that the top surface of the protective film located at the edge of the substrate is not lower than the top surface of the protective film located inside the substrate.

[0007] Optionally, the method for preparing the dielectric layer includes: coating a photoresist layer on the first surface of the substrate, and performing a first exposure process and a second exposure process on the photoresist layer, using the first exposure process to define a capping pattern for each chip area in the photoresist layer, and using the second exposure process to perform edge exposure so that the edge portion of the photoresist layer is retained to form the edge ring.

[0008] Optionally, the substrate has multiple chip areas, the chip area inside the substrate is a valid chip area, the chip area at the edge of the substrate is an invalid chip area, the area of ​​the invalid chip area constitutes the edge area of ​​the substrate, and the part of the protective film covering the edge area forms a convex ring structure.

[0009] Optionally, the protective film is completely attached to the edge of the substrate.

[0010] Optionally, the protective film covers a portion of the edge region of the substrate, so that an end portion of the protective film is retracted relative to an outer side wall of the substrate.

[0011] Optionally, the inward dimension of the end of the protective film relative to the outer side wall of the substrate is less than 3 mm.

[0012] Optionally, during the grinding process, the method further includes: spraying a cleaning liquid onto the periphery of the substrate to remove grinding debris accumulated on the periphery of the substrate.

[0013] Optionally, during the grinding process, a first nozzle is used to spray grinding liquid onto the second surface of the substrate for grinding the substrate; and a second nozzle is used to spray cleaning liquid onto the periphery of the substrate to remove grinding debris generated during the grinding process.

[0014] Optionally, after performing the grinding process, the method further includes: cleaning the side wall of the protective film to remove grinding debris on the side wall of the protective film.

[0015] Optionally, the protective film is a UV film, and before removing the protective film, the protective film is irradiated with a UV light source to reduce the viscosity of the protective film.

[0016] In the substrate thinning method provided by the present invention, the protective film on the substrate is improved so that the top surface of the protective film located at the edge of the substrate is not lower than the top surface of the protective film located inside the substrate, so that when the substrate is placed on the table of the grinding table, the edge portion of the protective film can be attached to the table to form a closed loop, avoiding the formation of a gap between the edge of the protective film and the table, and effectively blocking the grinding debris generated during the grinding process from entering and contacting the top surface of the protective film. Therefore, in the light source irradiation before peeling off the film, the edge portion of the protective film will not be blocked by the grinding debris and can be fully irradiated, ensuring that the protective film can be smoothly peeled off when peeling off the film. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of a substrate with a protective film attached.

[0018] Figure 2 For Figure 1 Schematic diagram of the substrate being polished.

[0019] Figure 3 It is a schematic flow chart of a method for thinning a substrate in one embodiment of the present invention.

[0020] Figure 4 FIG. 1 is a schematic structural diagram of a substrate having an edge ring formed thereon in an embodiment of the present invention.

[0021] Figure 5 The figure is a schematic structural diagram of a substrate to be polished with a protective film attached thereto in one embodiment of the present invention.

[0022] Figure 6 For Figure 5 Schematic diagram of the substrate being polished.

[0023] Figure 7 Another schematic diagram of the structure of a substrate to be polished with a protective film attached thereto in one embodiment of the present invention.

[0024] Figure 8 For Figure 7 Schematic diagram of the substrate being polished.

[0025] Fig. 9 It is a schematic structural diagram of a grinding device in one embodiment of the present invention.

[0026] The reference numerals are as follows:

[0027] 10 / 100-substrate;

[0028] 100A-Inner area;

[0029] 100B - marginal area;

[0030] 11 / 110- dielectric layer;

[0031] 110a - marginal ring;

[0032] 12 / 120-protective film;

[0033] 20-grinding table;

[0034] 30- grinding head;

[0035] 41-first nozzle;

[0036] 42-second nozzle;

[0037] 50-Grinding debris. DETAILED DESCRIPTION

[0038] As described in the background art, a protective film is required to protect the unpolished surface of the substrate during the grinding operation, and the protective film is removed after the grinding operation. However, the protective film is difficult to separate from the substrate during the removal process.

[0039] In this regard, the inventors of the present invention have discovered through research that an important reason why the protective film is difficult to separate from the substrate during peeling is that during the peeling operation, the viscosity between the protective film at the edge of the substrate and the substrate is still relatively high, making it difficult to separate the protective film.

[0040] For details, please refer to Figure 1 As shown in FIG. 1 , a plurality of film layers (e.g., dielectric layer 11) are usually formed on the surface of substrate 10, so that steps are generated on the surface of substrate 10. When protective film 12 is attached, the protective film 12 will conform to the steps and generate steps accordingly. When performing the grinding operation, the side of substrate 10 with protective film 12 attached is placed on grinding table 20 with the side facing the grinding table 20 (e.g., Figure 2 As shown in FIG. 1 , at this time, due to the presence of the step, there is a gap between the protective film 12 at some positions and the table surface of the grinding table 20, especially the gap between the protective film 12 at the edge of the substrate and the grinding table 20 is also exposed laterally, so that the grinding debris 50 generated during the grinding process can easily enter from the edge of the substrate 10 and accumulate on the protective film 12 at the edge of the substrate. For example, a large amount of silicon powder will be generated during the grinding process of silicon wafers, and the silicon powder can easily contact the top surface at the edge of the protective film.

[0041] After the grinding operation is completed, the protective film 12 is irradiated with a specific light source to reduce the viscosity of the protective film 12 on the substrate 10, so as to facilitate the protective film 12 to be removed from the substrate 10. However, since grinding debris 50 generated during the grinding process is accumulated on the protective film 12 at the edge of the substrate, the protective film 12 at the edge is not fully irradiated under the coverage of the grinding debris 50, resulting in the viscosity between the edge of the protective film 12 and the substrate 10 is still relatively large and difficult to be separated.

[0042] To this end, in the substrate thinning method provided by the present invention, the protective film on the substrate is creatively optimized to avoid the problem that the edge portion of the protective film cannot be separated from the substrate during the film peeling process due to the difficulty in fully irradiating the edge portion of the protective film.

[0043] Specifically, a method for thinning a substrate provided by the present invention may include: attaching a protective film on the first surface of the substrate, wherein the top surface of the protective film located in the edge area of ​​the substrate is not lower than the top surface of the protective film located in the inner area of ​​the substrate; placing the substrate on a grinding table with its first surface facing the grinding table, with the edge of the protective film attached to the table surface of the grinding table, and performing a grinding process on the second surface of the substrate to thin the thickness of the substrate; and irradiating the protective film with a specific light source to reduce the viscosity of the protective film on the substrate, and then removing the protective film.

[0044] That is, in the thinning method provided by the present invention, the top surface of the protective film located at the edge area of ​​the substrate has a higher height, so that when the substrate is placed on the table top of the grinding table, the edge portion of the protective film can be attached to the table top, so that the edge portion of the protective film can form a closed loop on the table top, avoiding the formation of a gap between the edge of the protective film and the table top, thereby effectively improving the grinding debris generated during the grinding process from entering the gap and adhering to the top surface of the protective film, ensuring that the protective film can be smoothly removed when the film is removed.

[0045] Furthermore, a dielectric layer can be formed on the first surface of the substrate, and a portion of the dielectric layer covering the edge of the substrate can be retained to form an edge ring, so that the edge ring can be used to increase the overall step height of the edge area of ​​the substrate, and the edge of the protective film can be attached to the edge ring with a higher step, thereby achieving a higher top surface height of the protective film located in the edge area of ​​the substrate.

[0046] Furthermore, the dielectric layer formed on the substrate may specifically include an organic material layer, which covers the chip area for sealing and protecting the device structure in the chip area, and also allows the portion of the organic material layer covering the edge of the substrate to be retained to form an edge ring. For example, the method for preparing the dielectric layer may include: first, coating a photoresist layer on the substrate; then, performing a first exposure process and a second exposure process on the photoresist layer, using the first exposure process to define the capping pattern of each chip area in the photoresist layer, and using the second exposure process to perform edge exposure so that the edge portion of the photoresist layer is retained to form an edge ring. In this example, the chip area is sealed and protected by the photoresist layer, and edge exposure can also be performed based on the photoresist layer to directly use the photoresist material at the edge to form an edge ring, which simplifies the preparation process of the edge ring, helps save costs, and improves production efficiency.

[0047] The following is a further detailed description of a substrate thinning method proposed in the present invention in conjunction with specific embodiments. According to the following description, the advantages and features of the present invention will become clearer. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. It should be recognized that relative terms such as "above", "below", "top", "bottom", "above" and "below" shown in the drawings can be used to describe the relationship between various elements. These relative terms are intended to cover different orientations of elements other than the orientations depicted in the drawings. For example, if the device is inverted relative to the view in the drawing, an element described as being "above" another element will now be below the element.

[0048] Figure 3 The schematic diagram of the process of the substrate thinning method in one embodiment of the present invention is as follows. Figure 3 The thinning method shown is used as an example to explain the thinning process in this embodiment. In practical applications, the thinning method can be applied to the thinning process of a substrate formed with an IGBT chip, for example.

[0049] First, step S100 is performed to provide a substrate 100 , and a protective film 120 is attached to a first surface of the substrate 100 , wherein the top surface of the protective film 120 located in the edge area 100B of the substrate 100 is not lower than the top surface of the protective film 120 located in the inner area 100A of the substrate 100 .

[0050] Specifically, the substrate 100 has a first surface and a second surface opposite to each other, the first surface is, for example, the front side of the substrate 100, and the second surface is the back side of the substrate 100. In this embodiment, a protective film 120 is attached to the front side of the substrate 100 to protect the front side structure of the substrate 100 when the back side of the substrate 100 is subsequently ground.

[0051] Furthermore, there are multiple chip areas on the substrate 100. Specifically, among the chip areas arranged on the substrate 100, due to the restrictions of the substrate shape and the chip shape, the chip area located at the edge of the substrate is usually an incomplete chip area, that is, an invalid chip area. For example, Figure 4 The substrate 100 shown is specifically a wafer, wherein the chips arranged at the edge of the wafer are incomplete chips. Therefore, the chip area located inside the substrate is usually a valid chip area, while the chip area located at the edge of the substrate is usually an invalid chip area. In this case, the invalid chip area at the edge of the substrate can be defined as the edge area 100B of the substrate 100. For example, the width of the invalid chip area at the edge of the substrate is 3 mm. In this case, the width of the substrate 100 from the edge to the inside of 3 mm can be defined as the edge area 100B of the substrate, and the inner side of the edge area 100B is the inner surrounding area 100A, and the inner surrounding area 100A has multiple valid chip areas.

[0052] When attaching the protective film 120, the portion of the protective film 120 covering the edge region 100B of the substrate 100 may have a higher top surface to form a convex ring structure. In a specific example, the method of attaching the protective film 120 on the first surface of the substrate 100 may include: forming a dielectric layer 110 on the first surface of the substrate 100, the dielectric layer 110 covering the chip area on the substrate 100 and also covering the edge region 100B of the substrate 100 to have an edge ring 110a; and attaching the protective film 120 on the first surface of the substrate 100, the edge of the protective film 120 being attached to the edge ring 110a of the dielectric layer 110, so that the top surface of the protective film 120 located at the edge of the substrate is not lower than the top surface of the protective film 120 located inside the substrate.

[0053] Combine the following Figure 4-Figure 5 and Figure 7 , an example is given to illustrate a method for attaching the protective film 120 in one embodiment.

[0054] First, a photoresist layer is coated on the first surface of the substrate 100. The material of the photoresist layer may include photosensitive polyimide. The photoresist layer is used to pattern the dielectric layer covering the chip area and the edge of the substrate 100 through an exposure process in subsequent steps.

[0055] Next, a first exposure process is performed on the photoresist layer to define a capping pattern for each chip region in the photoresist layer by the first exposure process. The photoresist material corresponding to the capping pattern covers the chip region on the substrate 100, and is used to cap the device structure in the chip region to achieve closed protection of the device structure.

[0056] Next, a second exposure process is performed on the photoresist layer to perform edge exposure, so that an edge portion of the photoresist layer is retained to form an edge ring 110 a.

[0057] like Figure 4 and Figure 5 As shown, the dielectric layer 110 in this embodiment is a photoresist layer, so that the edge exposure process, such as wafer edge exposure (WEE), can be directly used to retain the photoresist material at the edge of the substrate to form an edge ring 110a, which is conducive to simplifying the preparation process of the edge ring 110a and reducing production costs. For ease of understanding, Figure 4 Only the edge ring 110a covering the edge of the substrate in the dielectric layer 110 is shown, and other parts of the dielectric layer 110 are omitted, such as Figure 4 As shown, the edge ring 110 a continuously surrounds the edge region 100B of the substrate 100 .

[0058] It should be noted that the order of the first exposure process and the second exposure process described above is not limited. For example, the first exposure process may be performed first, and then the second exposure process may be performed on the edge of the substrate; or the second exposure process may be performed first on the edge of the substrate, and then the first exposure process may be performed; or the first exposure process and the second exposure process may be performed simultaneously.

[0059] Next, continue to refer to Figure 5 and Figure 7 As shown, a protective film 120 is attached to the first surface of the substrate 100, and the edge of the protective film 120 is attached to the edge ring 110a of the dielectric layer 110. Specifically, the dielectric layer 110 is formed on the substrate 100, so that a step is generated on the substrate 100, and the dielectric layer 110 has an edge ring 110a retained at the edge of the substrate, so that the surface of the substrate edge is raised, and the edge portion of the protective film 120 is correspondingly attached to the higher step surface.

[0060] In one example, for example Figure 5 As shown, the protective film 120 is completely attached to the edge ring 110a. In another example, for example Figure 7 As shown, the protective film 120 extends from the inside of the substrate to cover a portion of the edge ring 110a, so that the end of the protective film 120 is retracted relative to the outer wall of the edge ring 110a. It should be recognized that the retracted dimension of the end of the protective film 120 is smaller than the width dimension of the edge ring 110a to ensure that the end of the protective film 120 can still cover the top surface of the edge ring 110a. For example, if the width dimension of the edge ring is 3mm, the retracted dimension of the end of the protective film 120 is less than 3mm. Figure 7 , Figure 8In the example, since the end of the protective film 120 is retracted and the edge ring 110a provides a shielding effect, the grinding debris can be reduced from adhering to the side wall of the protective film 120 during the subsequent grinding process, and the use of the protective film material can be reduced, which is beneficial to cost saving.

[0061] In this embodiment, before attaching the protective film 120 to the substrate 100, a dielectric layer 110 is formed on the first surface of the substrate 100. The dielectric layer 110 covers the chip area on the substrate 100 and is used to cover the device structure in the chip area to achieve closed protection of the device structure. In addition, the dielectric layer 110 also covers the edge area 100B of the substrate 100 and has an edge ring 110a, which raises the overall step height of the edge area 100B of the substrate 100. In this way, when attaching the protective film 120, the edge of the protective film 120 can be attached to the edge ring 11a of the dielectric layer 110, and the overall step height of the edge portion of the protective film 120 is correspondingly raised, so that the edge portion of the protective film 120 can be attached to the grinding table during the grinding process to form a closed ring, effectively blocking the grinding debris generated during the grinding process, so that the protective film 120 can be smoothly removed from the substrate 100 after the thinning operation is completed. For details, please refer to step S200 and step S300.

[0062] In step S200, reference Figure 6 and Figure 8 As shown, the substrate 100 is placed on the table of the grinding table 20 with its first surface facing the grinding table 20, and the edge surface of the protective film 120 can be attached to the table.

[0063] In step S300 , the second surface of the substrate 100 is ground to reduce the thickness of the substrate 100 .

[0064] Specifically, for Figure 5 For the substrate 100 with the protective film attached, the edge of the protective film 120 completely covers the edge ring 110a, so that the edge of the substrate 100 is completely attached to the surface of the polishing table 20 without any edge gap (such as Figure 6 As shown), the grinding debris 50 can be effectively blocked from entering the bottom of the substrate 100, and accordingly the grinding debris 50 can be prevented from accumulating on the top surface of the protective film 120.

[0065] And, for Figure 7 For the substrate 100 with the protective film attached as shown, the edge of the protective film 120 only partially covers the edge ring 120, so even if there is still an edge gap between the edge of the substrate 100 and the table (such as Figure 8As shown), it should be recognized that the edge gap does not expose the top surface of the protective film 120, so even if grinding debris 50 enters the bottom of the substrate 100, it will not contact the top surface of the protective film 120; at the same time, due to the eaves shielding effect brought by the edge ring 110a, it can also effectively reduce the adhesion of grinding debris 50 to the side wall of the protective film 120, further improving the cleanliness of the protective film 120 and reducing the subsequent workload of cleaning the side wall of the protective film. In addition, the end of the protective film 120 is retracted, which also correspondingly reduces the use of protective film materials, which is conducive to cost saving.

[0066] In a further solution, during the grinding process, a cleaning liquid may be sprayed on the periphery of the substrate 100 to promptly remove the grinding debris 50 generated by grinding, thereby preventing the grinding debris 50 from accumulating in large quantities on the periphery of the substrate 100 and reducing the risk of the grinding debris 50 further remaining on the top surface of the protective film 120. In addition, by cleaning the periphery of the substrate 100, the grinding debris 50 adhering to the outer wall of the substrate 100 can be removed, effectively preventing the grinding debris 50 from being brought into the subsequent process along with the substrate 100 and causing pollution to the processing equipment and processing environment in the subsequent process.

[0067] In particular, in the case of Figure 7 and Figure 8 When the substrate 100 shown is being ground, there is still a gap between the edge of the substrate 100 and the table surface, so the grinding debris 50 can easily enter the gap. At this time, the generated grinding debris 50 can be promptly removed using a cleaning liquid, which can greatly reduce the amount of grinding debris 50 entering under the substrate, thereby further reducing the amount of grinding debris 50 adhering to the side wall of the protective film.

[0068] Fig. 9 The following diagram shows some structures of the grinding equipment, such as Fig. 9 As shown, the grinding device may include a grinding table 20, a grinding head 30, a first nozzle 41 and a second nozzle 42. The grinding table 20 is used to place the substrate 100; the grinding head 30 is used to grind the surface of the substrate 100; the first nozzle 41 is used to spray the grinding liquid onto the second surface of the substrate 100 to cooperate with the grinding head 30 to grind the substrate 100; the second nozzle 42 is used to spray the cleaning liquid onto the periphery of the substrate 100 to timely remove the grinding debris 50 generated during the grinding process. Further, the first nozzle 41 and the second nozzle 42 can be connected to the same liquid pipeline, so that the same cleaning liquid or grinding liquid can be sprayed. Alternatively, the first nozzle 41 and the second nozzle 42 can also be connected to different liquid pipelines respectively to control the liquid sprayed by the first nozzle 41 and the second nozzle 42 respectively.

[0069] In a further solution, after grinding the substrate 100, the side walls of the protective film 120 may be specially cleaned to further remove the grinding debris 50 that may remain on the side walls of the protective film after cleaning the periphery of the substrate 100 during the aforementioned grinding process. In one example, the side walls of the protective film 120 may be scrubbed, specifically by spraying a cleaning liquid on the protective film 120 and scrubbing it with a cleaning brush. For example, a cleaning liquid may be sprayed with a third nozzle, and the cleaning liquid may be sprayed onto the cleaning brush, which not only allows the cleaning brush to scrub with the cleaning liquid, but also allows the contaminants attached to the cleaning brush to be rinsed in time. At the same time, in addition to the rinsing force of the cleaning liquid, the scrubbing force of the cleaning brush may be used to completely clean the grinding debris that may remain on the side walls of the protective film.

[0070] In addition, after grinding the substrate 100, the ground substrate may be surface treated by etching, for example, SEZ treatment may be performed on the substrate 100 to reduce damage to the substrate surface and improve thickness uniformity during the thinning process.

[0071] Then, step S400 is performed, in which the protective film 120 is irradiated with a specific light source to reduce the viscosity of the protective film 120 on the substrate 100, and the protective film 120 is removed. In a specific example, the protective film 120 is, for example, a UV film, and UV light can be used to irradiate the protective film to reduce the viscosity of the protective film 120. It should be recognized that since there is no grinding debris left on the top surface of the edge of the protective film 120, the edge of the protective film 120 can also be fully irradiated by the light source, the viscosity can be effectively reduced, and it is easy to be removed from the substrate 100, thereby effectively improving the problem of the protective film 120 being difficult to remove and resulting in fragments.

[0072] It should be noted that, although the present invention has been disclosed as a preferred embodiment, the above embodiment is not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belongs to the scope of protection of the technical solution of the present invention.

[0073] It should also be understood that, unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the specification are only used to distinguish the various components, elements, steps, etc. in the specification, rather than to represent the logical relationship or sequential relationship between the various components, elements, steps, etc. It should also be recognized that the terms described herein are only used to describe specific embodiments, rather than to limit the scope of the present invention. It must be noted that the singular forms "one" and "a kind" used herein and in the appended claims include plural references unless the context clearly indicates the opposite meaning. For example, a reference to "a step" or "a device" means a reference to one or more steps or devices, and may include secondary steps and secondary devices. All conjunctions used should be understood in the broadest sense. And, the word "or" should be understood to have the definition of a logical "or", rather than a logical "exclusive or" definition, unless the context clearly indicates the opposite meaning.

Claims

1. A method for thinning a substrate, characterized in that: include: A protective film is attached to the first surface of the substrate, wherein the top surface of the protective film located in the edge region of the substrate is not lower than the top surface of the protective film located in the inner peripheral region of the substrate; Placing the substrate on a grinding table with its first surface facing the grinding table, with the edge of the protective film attached to the table surface of the grinding table, and performing a grinding process on the second surface of the substrate to reduce the thickness of the substrate; and The protective film is irradiated with a specific light source to reduce the viscosity of the protective film on the substrate, and then the protective film is removed.

2. The method for thinning a substrate as claimed in claim 1, characterized in that: The method of attaching a protective film on a first surface of a substrate comprises: forming a dielectric layer on the first surface of the substrate, wherein the dielectric layer covers the chip area on the substrate and also covers the edge area of ​​the substrate to have an edge ring; A protective film is attached to the first surface of the substrate, and the edge of the protective film is attached to the edge ring of the dielectric layer so that the top surface of the protective film at the edge of the substrate is not lower than the top surface of the protective film inside the substrate.

3. The method for thinning a substrate as claimed in claim 2, characterized in that: The method for preparing the dielectric layer comprises: A photoresist layer is coated on the first surface of the substrate, and a first exposure process and a second exposure process are performed on the photoresist layer. The first exposure process is used to define a capping pattern for each chip area in the photoresist layer, and the second exposure process is used to perform edge exposure so that the edge portion of the photoresist layer is retained to form the edge ring.

4. The method for thinning a substrate as claimed in claim 1, characterized in that: The substrate has multiple chip areas, the chip area inside the substrate is a valid chip area, the chip area at the edge of the substrate is an invalid chip area, the area of ​​the invalid chip area constitutes the edge area of ​​the substrate, and the part of the protective film covering the edge area forms a convex ring structure.

5. The method for thinning a substrate according to claim 1, wherein: The protective film is completely attached to the edge of the substrate.

6. The method for thinning a substrate according to claim 1, wherein: The protective film covers a portion of the edge region of the substrate, so that the end of the protective film is retracted relative to the outer side wall of the substrate.

7. The method for thinning a substrate as claimed in claim 6, characterized in that: The inward dimension of the end of the protective film relative to the outer side wall of the substrate is less than 3 mm.

8. The method for thinning a substrate as claimed in claim 1, characterized in that: During the grinding process, the method further includes spraying a cleaning liquid to the periphery of the substrate to remove grinding debris accumulated on the periphery of the substrate.

9. The method for thinning a substrate as claimed in claim 8, characterized in that: During the grinding process, a grinding liquid is sprayed onto the second surface of the substrate by using a first nozzle to grind the substrate; And, a cleaning liquid is sprayed onto the periphery of the substrate by using a second nozzle to remove grinding debris generated during the grinding process.

10. The method for thinning a substrate according to claim 1, wherein: After the grinding process is performed, the method further includes: cleaning the side wall of the protective film to remove grinding debris on the side wall of the protective film.

11. The method for thinning a substrate according to claim 1, wherein: The protective film is a UV film. Before removing the protective film, the protective film is irradiated with a UV light source to reduce the viscosity of the protective film.

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