Substrate thinning method

Abstract

The invention provides a method for thinning a substrate, which comprises the following steps of: providing a substrate comprising a plurality of cellular regions, each cellular region comprising an active region and a terminal region surrounding the active region; forming a middle support layer dividing the active area into a plurality of areas and a terminal isolation layer covering the upper surface of the terminal area on the upper surface of the cellular area; forming a protective layer covering the exposed surfaces of the middle support layer and the terminal isolation layer and the exposed upper surface of the active region; and thinning the substrate to a preset thickness from the bottom surface of the substrate, and removing the protective layer. According to the invention, the middle supporting layer which divides the active area into a plurality of areas and has the preset width is formed on the upper surface of the active area, so that the stress of the cellular area is uniform in the substrate thinning process, the subfissure of the area caused by the large stress of the terminal area is avoided, the quality of the substrate is ensured, and the yield of products is improved.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor integrated circuit manufacturing and relates to a substrate thinning method. Background Art

[0002] Fast Recovery Diode (FRD) is a power semiconductor device with good switching performance, short reverse recovery time, and soft recovery characteristics. At present, there is an increasing demand for FRD in the fields of high-voltage frequency conversion, industrial control, rectification, etc. These fields usually have large currents, which means that the chip area is large. In order to ensure the optimal performance of FRD devices, the silicon substrate should be thinned to a relatively thin degree. For example, the thickness of the silicon substrate in the FRD product with a withstand voltage of 650V is about 65μm, the thickness of the silicon substrate in the FRD product with a withstand voltage of 750V is about 75μm, the thickness of the silicon substrate in the FRD product with a withstand voltage of 1200V is about 120μm, and the thickness of the silicon substrate in the FRD product with a withstand voltage of 1700V is about 170μm. Large-sized chips are prone to hidden cracks when thinned to 120μm or less, and hidden cracks appear in the terminal area. Usually, a polyimide protective layer is provided on the upper surface of the terminal area of ​​the chip, resulting in a step difference between the active area and the terminal area. The terminal area of ​​a large-sized chip accounts for a small proportion of the area, and the pressure it is subjected to is greater. Compared with a small chip, it is more prone to hidden cracks, which in turn affects the yield and reliability of the chip. In the process of thinning the substrate of the FRD device, the hidden cracks in the terminal area of ​​the substrate are usually optimized by reducing the grinding speed, and the thinning speed has a lower limit. When the thickness of the silicon substrate is thin, the chip size is large, and the Polymide protective layer is thick, there is a risk of hidden cracks even when the slowest grinding speed is used, and the reduction in the thinning speed will also affect the product's production capacity.

[0003] Therefore, there is an urgent need to find a substrate thinning method that can prevent the fast recovery diode substrate from generating hidden cracks during the thinning process. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a substrate thinning method for solving the problem that hidden cracks are easily generated in the substrate of a large-size fast recovery diode chip during the thinning process in the prior art.

[0005] To achieve the above object and other related objects, the present invention provides a method for thinning a substrate, comprising the following steps:

[0006] Providing a substrate including a plurality of cell regions, wherein the cell region includes an active region and a terminal region surrounding the active region;

[0007] Forming an intermediate support layer dividing the active area into a plurality of areas and a terminal isolation layer covering the upper surface of the terminal area on the upper surface of the cell area;

[0008] forming a protective layer covering the exposed surfaces of the intermediate support layer and the terminal isolation layer and the exposed upper surface of the substrate;

[0009] The substrate is thinned from the bottom surface of the substrate to a preset thickness, and the protective layer is removed.

[0010] Optionally, the width of the intermediate support layer ranges from 500 μm to 1000 μm.

[0011] Optionally, the shape of the intermediate support layer includes a cross, a tic-tac-toe, a U-shape, and a Ⅴ shape.

[0012] Optionally, the difference between the thickness of the intermediate support layer and the thickness of the terminal isolation layer is not greater than 10% of the thickness of the terminal isolation layer.

[0013] Optionally, the protective layer includes a UV film layer.

[0014] Optionally, the thickness of the protective layer located on the upper surfaces of the intermediate supporting layer and the terminal isolation layer is not greater than 2 μm.

[0015] Optionally, thinning the substrate comprises the following steps:

[0016] Using a grinding tool with a first particle size and a first rotation speed to cut a first thickness from the back side of the substrate, and then using a first rotation speed and a first thinning speed to grind and thin the substrate to a second thickness from the back side of the substrate;

[0017] After the second thickness is reduced, the substrate is reduced to a third thickness by grinding at the first rotation speed and the second thinning speed, and then the substrate is reduced to a fourth thickness by grinding at the first rotation speed and the third thinning speed;

[0018] After the fourth thickness thinning is completed, the fifth thickness is cut from the back side of the substrate by using a grinding tool with a second particle size and a second rotation speed, and then the substrate is thinned to a sixth thickness by continuing the grinding at the second rotation speed and the fourth thinning speed;

[0019] After the sixth thickness thinning is completed, the substrate is thinned to a seventh thickness at the second rotation speed and the fifth thinning speed.

[0020] Optionally, the first particle size is larger than the second particle size.

[0021] Optionally, the first rotation speed is the same as the second rotation speed; the first thickness is the same as the fifth thickness.

[0022] Optionally, the first thinning speed is greater than the second thinning speed, the second thinning speed is greater than the third thinning speed; and the fourth thinning speed is greater than the fifth thinning speed.

[0023] As described above, the substrate thinning method of the present invention forms an intermediate support layer with a preset width on the upper surface of the active area to divide the active area into multiple areas. The thickness of the intermediate support layer is similar to or the same as that of the terminal isolation layer. The supporting effect of the intermediate support layer and the reasonably controlled thinning speed of the substrate make the forces on various parts of the cell area more uniform during the thinning of the substrate, reduce the pressure on the terminal area, avoid the terminal area being subjected to large and concentrated pressure, and cause hidden cracks inside the substrate under the action of large pressure, thereby ensuring the quality of the substrate during the thinning process, improving the yield of the product and the reliability of the diodes subsequently manufactured, and because the forces on various parts in the cell area are uniform, the quality of the substrate is ensured while the thinning speed is appropriately increased, thereby shortening the thinning time and improving the efficiency of the thinning process, which has a high industrial utilization value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A process flow chart showing a method for thinning a substrate according to the present invention is shown.

[0025] Figure 2 A schematic diagram showing the cross-sectional structure of a substrate in accordance with the substrate thinning method of the present invention.

[0026] Figure 3 It shows a schematic diagram of a top surface structure after forming an intermediate support layer and a terminal isolation layer in the substrate thinning method of the present invention.

[0027] Figure 4 It is a schematic diagram of another top surface structure after forming an intermediate support layer and a terminal isolation layer in the substrate thinning method of the present invention.

[0028] Figure 5 It is a schematic diagram showing a third top surface structure after forming an intermediate support layer and a terminal isolation layer in the substrate thinning method of the present invention.

[0029] Figure 6 Display as Figure 3 Schematic diagram of the cross-sectional structure.

[0030] Figure 7 Display as Figure 3 Schematic diagram of the cross-sectional structure after a protective layer is formed on the upper surface of the middle structure.

[0031] Figure 8 Display as Figure 7 Schematic diagram of the cross-sectional structure after removing the protective layer of the structure.

[0032] Description of Figure Numbers

[0033] 1 Substrate

[0034] 11 Cell area

[0035] 12 Active area

[0036] 13 Terminal Area

[0037] 2 Terminal isolation layer

[0038] 3. Intermediate support layer

[0039] 4. Protective layer DETAILED DESCRIPTION

[0040] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0041] See also Figures 1 to 8 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0042] This embodiment provides a method for thinning a substrate, such as Figure 1 As shown, it is a process flow chart of the substrate thinning method, which includes the following steps:

[0043] S1: providing a substrate including a plurality of cell regions, wherein the cell region includes an active region and a terminal region surrounding the active region;

[0044] S2: forming an intermediate support layer for dividing the active area into a plurality of areas and a terminal isolation layer for covering the upper surface of the terminal area on the upper surface of the cell area;

[0045] S3: forming a protective layer covering the exposed surfaces of the intermediate support layer and the terminal isolation layer and the exposed upper surface of the substrate;

[0046] S4: thinning the substrate from the bottom surface of the substrate to a preset thickness, and removing the protective layer.

[0047] See also Figures 2 to 6 , perform step S1 and step S2: provide a substrate 1 including a plurality of cell regions 11, the cell region 11 including an active region 12 and a terminal region 13 surrounding the active region 12; form an intermediate support layer 3 dividing the active region 12 into a plurality of regions and a terminal isolation layer 2 covering the upper surface of the terminal region 13 on the upper surface of the cell region 11.

[0048] Specifically, Figure 2 As shown, it is a schematic diagram of the cross-sectional structure of the substrate 1. Usually, the substrate 1 is a wafer to be thinned, and the wafer is a wafer to be manufactured into a fast recovery diode. Under the condition of ensuring the performance of the device to be manufactured later, the thickness, size and shape of the substrate 1 can be selected according to the actual situation; the number of cell regions 11 in the substrate 1 can be selected according to the actual situation; the size and shape of the cell region 11 can be selected according to the actual situation; the distance between two adjacent cell regions 11 can be selected according to the actual situation. In this embodiment, the initial thickness of the substrate 1 is 735μm.

[0049] Specifically, the size and shape of the active area 12 can be selected according to actual conditions while ensuring the performance of the device to be manufactured subsequently; the size and shape of the terminal area 13 surrounding the active area 12 can be selected according to actual conditions. Preferably, the shape of the active area 12 is a regular quadrilateral, and the terminal area 13 surrounding the active area 12 is a regular quadrilateral ring.

[0050] It should be noted that the terminal isolation layer 2 is usually used to protect the terminal area 13, and the terminal isolation layer 2 and the intermediate support layer 3 can be formed simultaneously or in steps.

[0051] Specifically, Figure 6 , which is a schematic diagram of the cross-sectional structure after forming the terminal isolation layer 2 and the intermediate support layer 3, the terminal isolation layer 2 is made of polyimide or other suitable materials. Preferably, the polyimide layer is used as the terminal isolation layer 2.

[0052] Specifically, while ensuring the performance of the subsequently formed device, the thickness and size of the terminal isolation layer 2 can be selected according to actual conditions. The size here refers to the size of the inner and outer rings of the terminal isolation layer 2. In this embodiment, the thickness of the terminal isolation layer 2 is 9 μm.

[0053] As an example, the width of the intermediate support layer 3 is in the range of 500 μm to 1000 μm. For example, the width of the intermediate support layer 3 may be 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 1000 μm.

[0054] Specifically, by disposing the intermediate support layer 3 , the area ratio of the support structure on the upper surface of the cell region 11 can be increased, thereby reducing the pressure intensity borne by the terminal region 13 during the subsequent thinning process of the substrate 1 .

[0055] Specifically, when the terminal isolation layer 2 and the intermediate supporting layer 3 are formed simultaneously, the formation of the terminal isolation layer 2 and the intermediate supporting layer 3 includes the following steps: forming a supporting material layer of a preset thickness on the upper surface of the substrate 1, and forming a patterned shielding layer covering the upper surface of the supporting material layer; etching the supporting material layer based on the patterned shielding layer to obtain the terminal isolation layer 2 covering the upper surface of the terminal area 13 and the intermediate supporting layer 3 located on the upper surface of the active area 12.

[0056] Specifically, the method of forming the support material layer includes coating or other suitable methods.

[0057] Specifically, the shielding layer is usually a photoresist layer, and the method of forming the shielding layer is a common photoresist coating, drying, exposure, and development process, which will not be described here.

[0058] Specifically, the method of etching the support material layer includes dry etching, wet etching or other suitable methods.

[0059] Specifically, when the terminal isolation layer 2 and the intermediate support layer 3 are formed simultaneously, after the terminal isolation layer 2 and the intermediate support layer 3 are formed, a protective layer is subsequently formed (see the following Figure 7 ), it also includes the step of removing the shielding layer. The method for removing the shielding layer is a commonly used photoresist stripping method, which will not be repeated here.

[0060] As an example, the difference between the thickness of the intermediate support layer 3 and the thickness of the terminal isolation layer 2 is not greater than 10% of the thickness of the terminal isolation layer 2, that is, when the intermediate support layer 3 and the terminal isolation layer 2 are formed in steps, the thickness of the intermediate support layer 3 and the terminal isolation layer 2 may have a thickness difference, but the difference is less than 10% of the thickness of the terminal isolation layer 2. Preferably, the intermediate support layer 3 is flush with the upper surface of the terminal isolation layer 2.

[0061] Specifically, when the terminal isolation layer 2 and the intermediate support layer 3 are formed in steps, the intermediate support layer 3 may be formed first, or the terminal isolation layer 2 may be formed first.

[0062] Specifically, the method of forming the intermediate support layer 3 includes coating, chemical vapor deposition, physical vapor deposition or other suitable methods.

[0063] Specifically, the material of the intermediate support layer 3 includes polyimide, silicon oxide, silicon nitride or other suitable materials. Preferably, the material of the intermediate support layer 3 is the same as that of the terminal isolation layer 2, so as to form the terminal isolation layer 2 and the intermediate support layer 3 simultaneously, reduce process steps, and save production costs.

[0064] Specifically, the shape of the middle support layer 3 includes a cross shape, a well shape, a circle shape, a rice shape or other suitable shapes. Preferably, the middle support layer 3 adopts a cross shape or a well shape, such as Figure 3 , Figure 4 and Figure 5 shown.

[0065] See also Figures 7 and 8 , perform steps S3 and S4: form a protective layer 4 covering the exposed surfaces of the intermediate support layer 3 and the terminal isolation layer 2 and the exposed upper surface of the substrate 1; thin the substrate 1 from the bottom surface of the substrate 1 to a preset thickness, and remove the protective layer 4.

[0066] Specifically, Figure 7 , which is a schematic diagram of the cross-sectional structure after the protection layer 4 is formed. The protection layer 4 is used to protect the front structure of the substrate 1 during the thinning process of the substrate 1 to avoid damage to the terminal isolation layer 2 and the front of the substrate 1.

[0067] As an example, the protective layer 4 includes a UV film layer or other suitable film layers. Preferably, a UV film is used as the protective layer 4 to facilitate the removal of the protective layer 4.

[0068] Specifically, the method for forming the protective layer 4 includes coating or other suitable methods. In this embodiment, a UV film material layer of a preset thickness is uniformly coated on the upper surface of the substrate 1 formed with the terminal isolation layer 2 and the intermediate support layer 3 through a coating process, and then the UV film layer material is UV cured to obtain the protective layer 4.

[0069] It should be noted that in the process of forming the UV film material layer, it is necessary to ensure that there are no bubbles between the UV film material layer and the exposed surfaces of the terminal isolation layer 2 and the intermediate support layer 3 and the upper surface of the substrate 1, so that the subsequently formed protective layer 4 has good adhesion with the terminal isolation layer 2, the intermediate support layer 3 and the substrate 1, thereby ensuring the protective performance of the protective layer 4.

[0070] As an example, the thickness of the protective layer 4 located on the upper surface of the intermediate support layer 3 and the terminal isolation layer 2 is not greater than 2 μm. Preferably, the thickness of the protective layer 4 covering the upper surface of the intermediate support layer 3 and the terminal isolation layer 2 is 1 μm.

[0071] Specifically, due to the formation of the intermediate support layer 3 on the front side of the substrate 1, the active area 12 is divided into a plurality of areas surrounded by the intermediate support layer 3 or enclosed by the terminal isolation layer 2 and the intermediate support layer 3. At the same time, since the height difference between the upper surface of the protective layer 4 above the intermediate support layer 3 and the upper surface of the protective layer 4 above the terminal isolation layer 2 is small or flush, through the support of the intermediate support layer 3, in the process of thinning the back side of the substrate 1, the stress on each area of ​​the cell area 11 is more uniform, thereby avoiding the terminal area 13 being subjected to a large and concentrated pressure in the process of thinning the substrate 1, resulting in hidden cracks in the substrate 1 in the area where it is located under the action of large pressure.

[0072] Specifically, the method for thinning the substrate 1 includes chemical mechanical polishing or other suitable methods. Preferably, the back side of the substrate 1 is thinned by a chemical mechanical polishing process.

[0073] As an example, thinning the substrate 1 includes the following steps: using a grinding tool with a first particle size and a first rotational speed to cut a first thickness from the back side of the substrate 1, and then grinding the back side of the substrate 1 to thin the substrate 1 to a second thickness at the first rotational speed and the first thinning speed; after the thinning of the second thickness is completed, grinding the substrate 1 to a third thickness at the first rotational speed and the second thinning speed, and then grinding the substrate 1 to a fourth thickness at the first rotational speed and the third thinning speed; after the thinning of the fourth thickness is completed, using a grinding tool with a second particle size and a second rotational speed to cut a fifth thickness from the back side of the substrate 1, and then continuing to grind the substrate 1 to a sixth thickness at the second rotational speed and the fourth thinning speed; after the thinning of the sixth thickness is completed, grinding the substrate 1 to a seventh thickness at the second rotational speed and the fifth thinning speed.

[0074] It should be noted that before thinning the substrate 1 , the substrate 1 needs to be fixed on a thinning device to facilitate grinding with a grinding tool.

[0075] As an example, the first particle size is larger than the second particle size, that is, thinning the substrate 1 by a grinding tool of the first particle size is equivalent to rough grinding in the thinning process, and thinning the substrate 1 by a grinding tool of the second particle size is equivalent to fine grinding in the thinning process of the substrate 1.

[0076] Specifically, under the condition of ensuring the safety of the substrate 1 during the thinning process, the particle size of the abrasive particles in the grinding tool with the first particle size can be selected according to actual conditions; the particle size of the abrasive particles in the grinding tool with the second particle size can be selected according to actual conditions.

[0077] As an example, the first rotation speed is the same as the second rotation speed; the first thickness is the same as the fifth thickness.

[0078] As an example, the first thinning speed is greater than the second thinning speed, the second thinning speed is greater than the third thinning speed; the fourth thinning speed is greater than the fifth thinning speed.

[0079] Specifically, the first speed ranges from 3500 rpm to 5500 rpm, the second speed ranges from 3500 rpm to 5500 rpm, the first thickness ranges from 40 μm to 60 μm, the second thickness ranges from 300 μm to 340 μm, the third thickness ranges from 50 μm to 70 μm, the fourth thickness ranges from 100 μm to 140 μm, the fifth thickness ranges from 40 μm to 60 μm, and the sixth thickness ranges from 20 μm to 350 μm. m~40μm, the seventh thickness range is 100μm~140μm, the first thinning speed range is 3.5μm / s~4.5μm / s, the second thinning speed range is 1.5μm / s~2.5μm / s, the third thinning speed range is 0.8μm / s~1.2μm / s, the fourth thinning speed range is 0.25μm / s~0.4μm / s, and the fifth thinning speed range is 0.1μm / s~0.2μm / s. In this embodiment, the first rotational speed and the second rotational speed are both 4500rpm, the first thickness and the fifth thickness are both 50μm, the second thickness is 320μm, the third thickness is 60μm, the fourth thickness and the seventh thickness are both 120μm, the sixth thickness is 30μm, the first thinning speed is 4μm / s, the second thinning speed is 2μm / s, the third thinning speed is 1μm / s, the fourth thinning speed is 0.3μm / s, and the fifth thinning speed is 0.2μm / s.

[0080] It should be noted that, in the rough grinding stage, the back side of the substrate 1 is firstly cut to make the back side of the substrate 1 evenly ground, and then the thinning speed is reduced for multiple times to reduce the corresponding thickness, so as to better control the roughness of the back side of the substrate 1 and avoid excessive wear or damage to the back side of the substrate 1. In the fine grinding stage, the first step is to cut to reduce the wear and accumulation of abrasives, ensure the grinding efficiency, and reduce the damage to the back side of the substrate 1. After the cutting, the thinning speed is reduced for multiple times to more finely control the material removal rate of the back side of the substrate 1, reduce the damage to the substrate 1, and ensure the quality of the substrate 1. At the same time, since the thickness of the thinned substrate 1 is related to the withstand voltage requirements of the diode device, etc., it is no longer limited here.

[0081] Specifically, Figure 8 , which is a schematic diagram of the cross-sectional structure after the protective layer 4 is removed. The method for removing the protective layer 4 is a commonly used UV adhesive stripping method, which will not be described in detail here.

[0082] It should be noted that after removing the protective layer 4, the step of continuing to perform the subsequent front structure manufacturing process of the fast recovery diode device on the front side of the substrate 1 is also included. Since the subsequent front structure manufacturing process of the fast recovery diode device is a conventional manufacturing process, it will not be repeated here.

[0083] Specifically, by arranging an intermediate support layer 3 with a preset width in the active area 12 to divide the active area 12 into multiple areas, and the thickness of the intermediate support layer 3 is similar to or the same as the terminal isolation layer 2, the supporting effect of the intermediate support layer 3 and the reasonable control of the thinning speed of the substrate 1 can make the pressure distribution of various areas of the cell area 11 more uniform, and at the same time reduce the pressure on the terminal area 13.

[0084] Specifically, the active area 12 is divided into multiple areas by the intermediate support layer 3. In the process of thinning the substrate 1, it is avoided that the upper surface of the protective layer 4 above the terminal area 13 is higher than the upper surface of the protective layer 4 above the active area 12, causing the substrate 1 in the terminal area 13 to be subjected to greater pressure and produce hidden cracks under the action of the greater pressure. The quality of the thinned substrate 1 and the reliability of the subsequently manufactured diode devices are ensured, and the yield of the devices is improved. In addition, since the force on the substrate 1 in the area where the cell area 11 is located is uniform, the quality of the substrate 1 in the thinning process is guaranteed, and the thinning speed of the substrate 1 can be appropriately increased while the thinning speed of the substrate 1 can be appropriately increased, thereby improving the efficiency of the substrate 1 thinning process to improve production capacity.

[0085] In summary, the substrate thinning method of the present invention forms an intermediate support layer with a preset width on the upper surface of the active area to divide the active area into multiple areas, and the thickness of the intermediate support layer is similar to or the same as that of the terminal isolation layer. The supporting effect of the intermediate support layer and the reasonable control of the thinning speed of the thinning process make the stress of the substrate in each area of ​​the cell area more uniform, reduce the pressure on the terminal area, avoid the terminal area from being subjected to large and concentrated pressure and causing hidden cracks, ensure the quality of the substrate, and improve the reliability of the diode device manufactured subsequently. In addition, since the stress of each area of ​​the cell area is relatively uniform, the speed of thinning the substrate can be appropriately increased while ensuring the quality of the substrate, thereby improving the efficiency of the thinning process. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has a high industrial utilization value.

[0086] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for thinning a substrate, characterized in that: The following steps are involved: Providing a substrate including a plurality of cell regions, wherein the cell region includes an active region and a terminal region surrounding the active region; Forming an intermediate support layer for dividing the active area into a plurality of areas and a terminal isolation layer covering the upper surface of the terminal area on the upper surface of the cell area; forming a protective layer covering the exposed surfaces of the intermediate support layer and the terminal isolation layer and the exposed upper surface of the substrate; The substrate is thinned from the bottom surface of the substrate to a preset thickness, and the protective layer is removed.

2. The method for thinning a substrate according to claim 1, characterized in that: The width of the intermediate support layer ranges from 500 μm to 1000 μm.

3. The method for thinning a substrate according to claim 1, characterized in that: The shapes of the intermediate support layer include a cross, a well, a U-shape, and a M-shape.

4. The method for thinning a substrate according to claim 1, characterized in that: The difference between the thickness of the intermediate support layer and the thickness of the terminal isolation layer is not greater than 10% of the thickness of the terminal isolation layer.

5. The method for thinning a substrate according to claim 1, characterized in that: The protective layer includes a UV film layer.

6. The method for thinning a substrate according to claim 1, characterized in that: The thickness of the protective layer located on the upper surfaces of the intermediate support layer and the terminal isolation layer is not greater than 2 μm.

7. The method for thinning a substrate according to claim 1, characterized in that: Thinning the substrate comprises the following steps: Using a grinding tool with a first particle size and a first rotation speed to cut a first thickness from the back side of the substrate, and then using a first rotation speed and a first thinning speed to grind and thin the substrate to a second thickness from the back side of the substrate; After the second thickness is reduced, the substrate is reduced to a third thickness by grinding at the first rotation speed and the second thinning speed, and then the substrate is reduced to a fourth thickness by grinding at the first rotation speed and the third thinning speed; After the fourth thickness thinning is completed, the fifth thickness is cut from the back side of the substrate by using a grinding tool with a second particle size and a second rotation speed, and then the substrate is thinned to a sixth thickness by continuing the grinding at the second rotation speed and the fourth thinning speed; After the sixth thickness thinning is completed, the substrate is thinned to a seventh thickness at the second rotation speed and the fifth thinning speed.

8. The method for thinning a substrate according to claim 7, characterized in that: The first particle size is larger than the second particle size.

9. The method for thinning a substrate according to claim 7, characterized in that: The first rotational speed is the same as the second rotational speed; The first thickness is the same as the fifth thickness.

10. The method for thinning a substrate according to claim 7, characterized in that: The first thinning speed is greater than the second thinning speed, the second thinning speed is greater than the third thinning speed; the fourth thinning speed is greater than the fifth thinning speed.

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