Method for thinning a wafer

Abstract

The application relates to a wafer thinning method, the wafer has a front surface and a back surface arranged oppositely, the wafer thinning method comprises the following steps: attaching an acid-resistant film to the front surface of the wafer; wherein the acid-resistant film completely covers the front surface of the wafer; grinding and thinning the back surface of the wafer until the thickness of the wafer reaches a target thickness; and performing a planarization treatment on the back surface of the wafer by using etching liquid. In the process of performing the planarization treatment on the back surface, the etching liquid can be prevented from penetrating into the front surface of the wafer to corrode the front surface of the wafer, the subsequent processing technologies such as evaporation and electrode manufacturing on the front surface of the wafer can be effectively avoided, and the semiconductor device failure caused by the corrosion of the front surface of the wafer by the etching liquid can be avoided.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a method for thinning a wafer. Background Technology

[0002] In related technologies, the chip stacking three-dimensional packaging process includes wafer thinning process. The wafer thinning process usually includes the process of grinding and thinning the back of the wafer and the process of etching the back of the wafer. However, when the wafers produced by the traditional wafer thinning process are used to manufacture semiconductor devices, the reliability of the semiconductor devices may fail. Summary of the Invention

[0003] Therefore, it is necessary to provide a wafer thinning method to address the problem that semiconductor devices may fail due to the reliability issues arising from wafers produced by traditional wafer thinning processes during semiconductor device fabrication.

[0004] To achieve the above objectives, the present invention provides a wafer thinning method, wherein the wafer has a front side and a back side disposed opposite to each other, the thinning method comprising:

[0005] An acid-resistant film is applied to the front side of the wafer; wherein the acid-resistant film completely covers the front side of the wafer.

[0006] The back side of the wafer is thinned by grinding until the wafer reaches the target thickness;

[0007] The back side of the wafer is planarized using an etching solution.

[0008] In one embodiment, the acid-resistant membrane includes an acid-resistant base layer and an adhesive layer stacked together;

[0009] The step of attaching the acid-resistant film to the front side of the wafer includes:

[0010] The acid-resistant base layer is bonded to the front side of the wafer via the adhesive layer.

[0011] In one embodiment, the acid-resistant base layer is made of a polyolefin copolymer.

[0012] In one embodiment, the thickness of the acid-resistant base layer is greater than or equal to 90 μm; and / or

[0013] The thickness of the adhesive layer is greater than or equal to 30 μm.

[0014] In one embodiment, attaching the acid-resistant film to the front side of the wafer includes:

[0015] The acid-resistant film is pressed onto the front side of the wafer using rollers.

[0016] In one embodiment, the acid-resistant film includes a first portion that completely covers the front side of the wafer, and a second portion that surrounds the first portion;

[0017] The process of attaching the acid-resistant film to the front side of the wafer further includes:

[0018] The cutting head is heated, and the acid-resistant membrane is cut using the heated cutting head to separate the second part from the first part.

[0019] In one embodiment, planarizing the back side of the wafer using an etching solution includes:

[0020] The wafer is immersed in the etching solution and left to stand for a first preset time to planarize the back side of the wafer.

[0021] The etching solution includes hydrofluoric acid, sulfuric acid, and nitric acid.

[0022] In one embodiment, the first preset time is less than or equal to 3 minutes.

[0023] In one embodiment, after planarizing the back side of the wafer using an etching solution, the process further includes:

[0024] The wafer is cleaned using pure water at a preset temperature.

[0025] In one embodiment, the preset water temperature is less than or equal to 50°C.

[0026] In one embodiment, the cleaning time for cleaning the wafer does not exceed 6 minutes.

[0027] In one embodiment, the etching solution includes an acidic solution with oxidizing properties; the step of cleaning the wafer with pure water at a preset temperature further includes:

[0028] Remove the oxide film layer on the back side of the wafer.

[0029] In one embodiment, removing the oxide film layer on the back side of the wafer includes:

[0030] The wafer is immersed in hydrofluoric acid solution and left to stand for a second preset time to remove the oxide film layer on the back side of the wafer.

[0031] The second preset time is less than or equal to 3 minutes.

[0032] In one embodiment, the process of removing the oxide film layer on the back side of the wafer further includes:

[0033] The wafer is cleaned at least once with pure water at a preset temperature;

[0034] The wafer is dried.

[0035] The acid-resistant film is removed from the wafer.

[0036] The above-mentioned wafer thinning method, because the acid-resistant film is applied and completely covers the front side of the wafer, can form a protective layer on the front side of the wafer, preventing the etching solution from penetrating into the front side of the wafer and corroding it during the planarization process of the back side. It can also effectively avoid affecting subsequent processing processes such as evaporation and electrode fabrication on the front side of the wafer, and can also prevent semiconductor device failure caused by the etching solution corroding the front side of the wafer. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 A schematic flowchart of the wafer thinning method in the first embodiment of this application is shown;

[0039] Figure 2 A schematic diagram of the structure of the wafer and the acid-resistant film in one embodiment of this application is shown;

[0040] Figure 3 A schematic flowchart of the wafer thinning method in the second embodiment of this application is shown;

[0041] Figure 4 A schematic diagram of the structure of the wafer, acid-resistant film, and roller in one embodiment of this application is shown;

[0042] Figure 5 This illustration shows a schematic diagram of the structure when the acid-resistant film completely covers the wafer in one embodiment of this application;

[0043] Figure 6 A schematic diagram of the structure of the wafer and the acid-resistant film in another embodiment of this application is shown;

[0044] Figure 7 It shows Figure 6 An enlarged view of point A;

[0045] Figure 8 A schematic flowchart of the wafer thinning method in the third embodiment of this application is shown;

[0046] Figure 9 A schematic flowchart of the wafer thinning method in the fourth embodiment of this application is shown;

[0047] Figure 10 A schematic flowchart of the wafer thinning method according to the fifth embodiment of this application is shown.

[0048] Explanation of reference numerals in the attached figures: 210, wafer; 211, front side; 212, back side; 220, acid-resistant film; 221, acid-resistant base layer; 222, adhesive layer; 230, roller; 2201, first part; 2202, second part. Detailed Implementation

[0049] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0051] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, parts, regions, layers, doping types, and / or portions, these elements, parts, regions, layers, doping types, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, part, region, layer, doping type, or portion from another element, part, region, layer, doping type, or portion. Therefore, without departing from the teachings of this invention, the first element, component, region, layer, doping type, or portion discussed below may be represented as a second element, component, region, layer, or portion; for example, the first doping type may be referred to as the second doping type, and similarly, the second doping type may be referred to as the first doping type; the first doping type and the second doping type are different doping types, for example, the first doping type may be P-type and the second doping type may be N-type, or the first doping type may be N-type and the second doping type may be P-type.

[0052] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as “below,” “under,” or “below” will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both above and below orientations. Furthermore, the device may also include other orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.

[0053] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, in this specification, the term “and / or” includes any and all combinations of the associated listed items.

[0054] The inventors of this application discovered through research that in traditional wafer thinning processes, etching solutions (such as strong acids) are typically used to etch the back side of the wafer. This causes the front side of the wafer to be easily corroded by the etching solution (such as strong acids) during the etching process (invisible to the naked eye), which in turn affects subsequent processing processes such as evaporation and electrode fabrication on the front side of the wafer. It can even cause semiconductor devices to experience increased leakage current and decreased breakdown voltage after a period of use, resulting in reliability failure of the semiconductor device.

[0055] It should be noted that since the situation of "the front side of the wafer being corroded by the etching solution (such as strong acid) during the etching process on the back side of the wafer" is invisible to the naked eye, it is understandable that this situation is not easy to detect, and therefore it is not easy to find the cause of the reliability failure of the semiconductor device. However, after verifying with a large amount of experimental data, the inventors of this application have concluded that "the situation of the front side of the wafer being corroded by the etching solution (such as strong acid) during the etching process on the back side of the wafer" will lead to the reliability failure of the semiconductor device.

[0056] To address the problem of semiconductor device reliability failure caused by strong acid corrosion on the front side of the wafer, the inventors of this application further conducted in-depth research and applied an acid-resistant film to the front side of the wafer during the wafer thinning process. This effectively prevents the etching solution from penetrating to and corroding the front side of the wafer during the wafer thinning process, thereby improving the reliability of the semiconductor device.

[0057] Figure 1 A schematic flowchart of a wafer thinning method according to an embodiment of this application is shown. Figure 2 A schematic diagram of the structure of the wafer and the acid-resistant film in one embodiment of this application is shown.

[0058] In some embodiments, please refer to Figure 1 and Figure 2 This invention provides a wafer thinning method, comprising the following steps:

[0059] S110, A wafer 210 is provided; wherein the wafer 210 has a front side 211 and a back side 212 disposed opposite to each other.

[0060] S120. The acid-resistant film 220 is attached to the front side 211 of the wafer 210. The acid-resistant film 220 completely covers the front side 211 of the wafer 210.

[0061] S130. The back side 212 of wafer 210 is ground and thinned until the thickness of wafer 210 reaches the target thickness. The target thickness can be set according to the required thickness of wafer 210. For example, if the initial thickness of wafer 210 is 750 μm and the target thickness is 200 μm, then the back side 212 of wafer 210 is ground and thinned until the thickness of wafer 210 reaches 200 μm.

[0062] S140. Planarize the back surface 212 of wafer 210 using an etching solution. During the grinding and thinning process of the back surface 212 of wafer 210, a rough surface is formed on the back surface 212 of the wafer. Therefore, planarizing the back surface 212 of wafer 210 using an etching solution can make the rough surface formed by grinding smooth, which can effectively reduce the contact resistance.

[0063] It is understood that in the wafer thinning method of this application, since the acid-resistant film 220 is applied and completely covers the front side 211 of the wafer 210, the acid-resistant film 220 can form a protective layer on the front side 211 of the wafer 210, preventing the etching solution from penetrating into the front side 211 of the wafer 210 and corroding the front side 211 of the wafer 210 during the planarization process of the back side 212. It can also effectively avoid affecting the subsequent processing processes such as evaporation and electrode fabrication on the front side of the wafer, and can also prevent the semiconductor device from failing due to the etching solution corroding the front side 210 of the wafer 210.

[0064] In some embodiments, the etching solution may be at least one of hydrofluoric acid, sulfuric acid and nitric acid, or other liquids that can smooth the rough surface formed on the back side 212 of the wafer, without any specific limitation.

[0065] In some embodiments, please refer to Figure 2 The acid-resistant film 220 includes an acid-resistant base layer 221 and an adhesive layer 222 stacked together. The step S120 of attaching the acid-resistant film 220 to the front side 211 of the wafer 210 includes: attaching the acid-resistant base layer 221 to the front side 211 of the wafer 210 through the adhesive layer 222, so that the acid-resistant film 220 is attached and completely covers the front side 211 of the wafer 210.

[0066] The acid-resistant base layer 221 is sealed to the front side 211 of the wafer 210 through the adhesive layer 222, and the whole formed by the acid-resistant base layer 221 and the adhesive layer 222 can completely cover the front side 211 of the wafer 210. In this way, the front side 211 of the wafer 210 can be protected to better prevent the etching solution from corroding the front side 211 of the wafer 210 during the planarization process of the back side 212.

[0067] In some embodiments, the acid-resistant base material may be a polyolefin copolymer or other material that can prevent the etching solution from corroding the front side 211 of the wafer 210, without specific limitations.

[0068] In some embodiments, the acid-resistant base material includes a polyolefin copolymer, which can effectively prevent the etching solution from corroding the front side 211 of the wafer 210.

[0069] In some embodiments, the thickness of the acid-resistant substrate 221 is greater than or equal to 90 μm. If the thickness of the acid-resistant substrate 221 is too small, the etching solution can easily penetrate through the acid-resistant substrate 221 to the front side 211 of the wafer 210. Therefore, the thickness of the acid-resistant substrate 221 needs to be large enough, for example, greater than or equal to 90 μm, to ensure that the etching solution does not easily penetrate through the acid-resistant substrate 221 to the front side 211 of the wafer 210.

[0070] In some embodiments, the thickness of the adhesive layer 222 is greater than or equal to 30 μm. If the thickness of the adhesive layer 222 is too small, the adhesion of the acid-resistant base layer 221 will be insufficient, and the etching solution will easily penetrate from between the adhesive layer 222 and the wafer 210 to the front side 211 of the wafer 210. Therefore, the thickness of the adhesive layer 222 needs to be large enough, for example, the thickness of the adhesive layer 222 should be greater than or equal to 30 μm, so that the etching solution will not easily penetrate from between the adhesive layer 222 and the wafer 210 to the front side 211 of the wafer 210, and the acid-resistant base layer 221 will be firmly sealed to the front side 211 of the wafer 210.

[0071] In some embodiments, the thickness of the acid-resistant base layer 221 is greater than or equal to 90 μm, and the thickness of the adhesive layer 222 is greater than or equal to 30 μm. This configuration ensures that, on the one hand, the etching solution does not easily penetrate through the acid-resistant base layer 221 to the front side 211 of the wafer 210, and on the other hand, it ensures that the etching solution does not easily penetrate from the sidewall of the adhesive layer 222 to the front side 211 of the wafer 210, while also ensuring that the acid-resistant base layer 221 is firmly and securely sealed to the front side 211 of the wafer 210.

[0072] In some embodiments, the adhesive layer 222 may be a UV-curable adhesive. The UV-curable adhesive has suitable adhesion to ensure that the acid-resistant base layer 221 is firmly and sealed to the front side 211 of the wafer 210, preventing the etching solution from penetrating from between the adhesive layer 222 and the wafer 210 to the front side 211 of the wafer 210. Of course, the adhesive layer 222 may also be made of other materials that can firmly and sealed the acid-resistant base layer 221 to the front side 211 of the wafer 210, and no specific limitation is made here.

[0073] In some embodiments, please refer to Figure 3 and Figure 4Step S120, which involves attaching the acid-resistant film 220 to the front side 211 of the wafer 210, includes:

[0074] S1201, Select acid-resistant membrane 220.

[0075] S1202, The acid-resistant film 220 is pressed onto the front side 211 of the wafer 210 by the roller 230, so that the acid-resistant film 220 is applied and completely covers the front side 211 of the wafer 210.

[0076] The acid-resistant film 220 is pressed onto the front side 211 of the wafer 210 by the rolling action of the roller 230, so that the acid-resistant film 220 can be applied and completely cover the front side 211 of the wafer 210.

[0077] In some embodiments, the rolling pressure applied by the roller 230 to the wafer 210 is 0.1-0.3 MPa. If the rolling pressure applied by the roller 230 to the wafer 210 is too small, the acid-resistant film 220 will not adhere firmly. If the rolling pressure applied by the roller 230 to the wafer 210 is too large, it will affect the quality of the wafer and may also cause adhesive residue to remain on the wafer 210 during the film removal process. Therefore, it is necessary to control the rolling pressure applied by the roller 230 to the wafer 210 within a suitable range, such as 0.1-0.3 MPa, so as to ensure that the acid-resistant film 220 is firmly bonded to the front side 211 of the wafer 210 and to avoid adhesive residue on the wafer 210 during film removal.

[0078] In some embodiments, please refer to Figure 3 and Figure 5 The acid-resistant film 220 includes a first portion 2201 that completely covers the front side 211 of the wafer 210, and a second portion 2202 surrounding the first portion 2201. Following step S120 of attaching the acid-resistant film 220 to the front side 211 of the wafer 210, the process further includes:

[0079] S121. Heat the cutting head and use the heated cutting head to cut the acid-resistant membrane 220 to remove and separate the second part 2202 from the first part 2201.

[0080] It is understandable that using a heated cutting head makes it easier to cut off the second part 2202 of the acid-resistant film 220, making the edge of the first part 2201 flat, and ensuring that the retained first part 2201 completely covers the front side 211 of the wafer 210.

[0081] In some embodiments, the first portion 2201 includes a portion of the acid-resistant base layer 221 and a portion of the adhesive layer 222, and the second portion 2202 includes another portion of the acid-resistant base layer 221 and another portion of the adhesive layer 222. The heated cutting head enables at least partial melting of the adhesive layer 222 of the acid-resistant film 220, so that the adhesive layer 222 of the acid-resistant film 220, guided by the cutting force of the cutting head, can cover the top of the wafer 210 to form an enclosure around the front side 211 of the wafer 210 (e.g., ...). Figure 6 and Figure 7 As shown), after the adhesive layer 222 is cured, it can better prevent the etching solution from penetrating from between the adhesive layer 222 and the wafer 210 to the front side 211 of the wafer 210.

[0082] In some embodiments, the temperature of the heated cutting head is 70-120°C. If the temperature of the heated cutting head is too low, it will be difficult to cut off the second part 2202 of the acid-resistant film 220. If the temperature of the heated cutting head is too high, the acid-resistant film 220 will melt excessively, affecting the bonding effect. Therefore, the temperature of the heated cutting head needs to be controlled within a suitable temperature range, such as 70-120°C. This ensures that the heated cutting head can easily cut off the second part 2202 of the acid-resistant film 220, making the edge of the first part 2201 flat, while also ensuring that the retained first part 2201 completely covers the front side 211 of the wafer 210, resulting in a better bonding effect.

[0083] In some embodiments, please refer to Figure 8 Step S140, which involves planarizing the back surface 212 of wafer 210 using an etching solution, includes:

[0084] S141. Immerse wafer 210 in etching solution and leave it for a first preset time to planarize the back side 21 of wafer 210. The etching solution includes hydrofluoric acid, sulfuric acid and nitric acid.

[0085] Hydrofluoric acid, sulfuric acid and nitric acid combine to form a strong acid mixture, which is highly corrosive and can planarize the back side 21 of wafer 210 in a short time. It is understood that the first preset time is short, that is, the time when wafer 210 is placed in the etching solution is short. In this way, the etching solution can be better prevented from penetrating to the front side 211 of wafer 210.

[0086] In some embodiments, step S140 of planarizing the back surface 212 of the wafer 210 using an etching solution includes:

[0087] Multiple wafers 210 are immersed in the etching solution in an etching tank and left to stand for a first preset time to planarize the back surface 21 of the wafers 210. The etching solution includes hydrofluoric acid, sulfuric acid, and nitric acid. This allows for simultaneous planarization of the back surface 21 of multiple wafers 210, improving the efficiency of the planarization process. For example, 12 wafers 210 can be immersed in the etching solution in the etching tank.

[0088] In some embodiments, the first preset time should not be too long to avoid the wafer 210 being placed in the etching solution for too long. Therefore, the first preset time is set to less than or equal to 3 minutes, which can effectively planarize the back side 21 of the wafer 210 and effectively prevent the etching solution from penetrating to the front side 211 of the wafer 210.

[0089] It should be noted that this application adopts the method of "wafer 210 being placed in etching solution", which abandons the method of shaking the wafer up and down in the traditional back cleaning process, and avoids the etching solution from penetrating the front side 211 of the wafer 210 more easily due to shaking the wafer up and down.

[0090] In some embodiments, please refer to Figure 8 After step S140, which involves planarizing the back surface 212 of wafer 210 using an etching solution, the process further includes:

[0091] S150. Use pure water with a preset water temperature to clean the wafer 210.

[0092] To avoid the temperature of the residual etching solution on the wafer rising due to excessively high pure water temperature, and thus to prevent the residual etching solution from penetrating more easily to the front side 211 of the wafer 210 due to the increased etching rate of the etching solution at excessively high temperature.

[0093] In some embodiments, the preset water temperature is less than or equal to 50°C.

[0094] To avoid the residual etching solution from getting too hot, it is also effective to prevent the etching solution from penetrating to the front side 211 of the wafer 210.

[0095] In some embodiments, the cleaning time for wafer 210 does not exceed 6 minutes. The cleaning time for wafer 210 should not be too long to avoid problems such as poor adhesion of the acid-resistant film 220 due to excessive cleaning time.

[0096] In some embodiments, step S150 of cleaning the wafer 210 with pure water at a preset temperature includes: performing a first cleaning of the wafer using a nozzle; wherein the nozzle faces the back side 212 of the wafer 210 and the nozzle is capable of spraying pure water at a preset temperature.

[0097] The wafer 210 is rinsed selectively to prevent the etching solution from being flushed between the acid-resistant film 220 and the front side 211 of the wafer 210 due to the impact force of the nozzle on the wafer.

[0098] It should be noted that during the first cleaning of wafer 210, the nozzle should be kept away from the sidewall of the acid-resistant film 220 to avoid the etching solution being flushed between the acid-resistant film 220 and the front side 211 of wafer 210 due to the impact force of the nozzle on the acid-resistant film 220.

[0099] In some embodiments, the etching solution comprises an acidic solution with oxidizing properties; see [link to relevant documentation]. Figure 8 After step S150, which involves cleaning the wafer 210 with pure water at a preset temperature, the process further includes:

[0100] S160, Remove the oxide film layer on the back side 212 of wafer 210.

[0101] The acidic solution in the etching solution has oxidizing properties. When the back side 212 of the wafer 210 is planarized using the etching solution, it is equivalent to performing wet etching on the back side 212 of the wafer 210. Thus, the oxidizing acidic solution will cause an oxide film layer to form on the back side 212 of the wafer 210, which needs to be removed.

[0102] In some embodiments, the etching solution includes sulfuric acid, nitric acid, and hydrofluoric acid, wherein the oxidizing acidic solutions are sulfuric acid and nitric acid. During the planarization process of the back side 212 of the wafer 210 using the etching solution, the strongly oxidizing sulfuric acid and nitric acid can cause an oxide film layer to form on the back side 212 of the wafer 210. Of course, the etching solution can also be other oxidizing acidic solutions, which are not specifically limited here.

[0103] In some embodiments, please refer to Figure 8 and Figure 9 Step S160, which involves removing the oxide film layer on the back side 212 of wafer 210, includes:

[0104] S161. Immerse wafer 210 in hydrofluoric acid solution and let it stand for a second preset time to remove the oxide film layer on the back side 212 of wafer 210. The second preset time is less than or equal to 3 minutes.

[0105] It is understood that the material of wafer 210 is Si, and the oxide film layer on the back side 212 of wafer 210 is usually SiO2. Combining the reaction SiO2 + 6HF → H2SiF6 + 2H2O, hydrofluoric acid solution can effectively remove the oxide film layer on the back side 212 of wafer 210. Furthermore, hydrofluoric acid has a small molecular weight and easily penetrates wafer 210. Therefore, the second preset time should not be too long; it can be set to less than or equal to 3 minutes to prevent hydrofluoric acid molecules from penetrating to the front side 211 of wafer 210.

[0106] It should be added that, during the process of immersing the wafer in the hydrofluoric acid solution, if the hydrofluoric acid solution is placed in the pickling tank, the practice of circulating the hydrofluoric acid solution into the pickling tank by a circulation pump should be abandoned. Instead, an appropriate amount and concentration of hydrofluoric acid solution can be pumped into the pickling tank, the circulation pump can be turned off, and then the wafer can be immersed in the hydrofluoric acid solution and left to stand for a second preset time to prevent the circulating hydrofluoric acid solution from penetrating to the front side 211 of the wafer 210.

[0107] In some embodiments, please refer to Figure 9 and Figure 10 After step S160, which removes the oxide film layer on the back side 212 of wafer 210, the thinning method further includes:

[0108] The wafer 210 is cleaned at least once with pure water at a preset temperature.

[0109] The wafer 210 is dried.

[0110] Remove the acid-resistant film 220 from the wafer 210.

[0111] Specifically, such as Figure 9 In the embodiment shown, after step S160 of removing the oxide film layer on the back side 212 of wafer 210, the thinning method further includes:

[0112] S170. Use pure water with a preset temperature to clean the wafer 210 again.

[0113] S180, Dry wafer 210.

[0114] S190, Remove the acid-resistant film 220 from the wafer 210.

[0115] Specifically, such as Figure 10 In the embodiment shown, after step S260 of removing the oxide film layer on the back side 212 of wafer 210, the thinning method further includes:

[0116] S270. The wafer 210 is cleaned multiple times with pure water at a preset temperature. The multiple times in step S270 can be two separate cleanings with pure water at a preset temperature, or three or more cleanings with pure water at a preset temperature. No specific limitation is made here.

[0117] S280, Dry wafer 210.

[0118] S290, Remove the acid-resistant film 220 from the wafer 210.

[0119] By cleaning the wafer 210 multiple times, residual hydrofluoric acid solution can be effectively prevented from penetrating to the front side 211 of the wafer 210, and the surface of the wafer 210 can be made cleaner.

[0120] In some embodiments, the cleaning time for each cleaning of wafer 210 shall not exceed 6 minutes, and the cleaning time for each cleaning of wafer 210 shall not be too long, so as to avoid the acid-resistant film 220 from not adhering properly due to excessive cleaning time.

[0121] In some embodiments, please refer to Figure 10 Thinning methods include:

[0122] S210, a wafer 210 is provided; wherein the wafer 210 has a front side 211 and a back side 212 disposed opposite to each other.

[0123] S220, Apply the acid-resistant film 220 to the front side 211 of the wafer 210.

[0124] S230. Grind and thin the back side 212 of wafer 210 until the thickness of wafer 210 reaches the target thickness.

[0125] S240. Planarize the back surface 212 of wafer 210 using an etching solution. Specifically, wafer 210 can be immersed in the etching solution and left to stand for a first preset time to planarize the back surface 212 of wafer 210. The etching solution includes hydrofluoric acid, sulfuric acid, and nitric acid. The first preset time is equal to 2 minutes.

[0126] S250. The wafer 210 is cleaned with pure water at a preset temperature of 25°C.

[0127] S260. Remove the oxide film layer on the back side 212 of the wafer 210. Specifically, the wafer 210 can be immersed in a hydrofluoric acid solution and left to stand for a second preset time to remove the oxide film layer on the back side 212 of the wafer 210. The second preset time is equal to 2 minutes.

[0128] S270. The wafer 210 is cleaned multiple times with pure water at a preset temperature of 25°C.

[0129] S280, Dry wafer 210.

[0130] S290, Remove the acid-resistant film 220 from the wafer 210.

[0131] In the wafer thinning method of this application, since the acid-resistant film 220 is applied and completely covers the front side 211 of the wafer 210, the acid-resistant film 220 can form a protective layer on the front side 211 of the wafer 210, preventing the etching solution from penetrating into the front side 211 of the wafer 210 and corroding the front side 211 of the wafer 210 during the planarization process of the back side 212. It can also effectively avoid affecting subsequent processing processes such as evaporation and electrode fabrication on the front side of the wafer, and can also prevent semiconductor device failure caused by the etching solution corroding the front side 210 of the wafer 210. This can broaden the application range of the wafer structure obtained by this thinning method.

[0132] In some embodiments, after the wafer 210 is thinned using the wafer thinning method of this application, metals such as Ti, Ni or Ag can be deposited on the back side 212 of the wafer 210, which can effectively reduce the on-resistance and thermal effect of the chip, reduce energy consumption and ensure the reliability of the chip.

[0133] It should be understood that, although Figure 1 , Figure 3 and Figures 8-10 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 1 , Figure 3 and Figures 8-10 At least some of the steps in the process may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but may be executed at different times. The execution order of these steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least some of the steps or stages in other steps.

[0134] In the description of this specification, references to terms such as "some embodiments," "other embodiments," "ideal embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0135] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0136] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for thinning a wafer, the wafer having a front side and a back side disposed opposite to each other, characterized in that, The thinning method includes: An acid-resistant film is applied to the front side of the wafer; wherein the acid-resistant film completely covers the front side of the wafer. The back side of the wafer is thinned by grinding until the wafer reaches the target thickness; The back side of the wafer is planarized using an etching solution; The acid-resistant film includes a first portion that completely covers the front side of the wafer, and a second portion that surrounds the first portion; The process of attaching the acid-resistant film to the front side of the wafer further includes: The cutting head is heated, and the acid-resistant membrane is cut using the heated cutting head to separate the second part from the first part; The temperature of the heated cutting head is 70-120℃; The acid-resistant film includes an acid-resistant base layer and an adhesive layer stacked together; the heated cutting head can at least partially melt the adhesive layer of the acid-resistant film so that the adhesive layer of the acid-resistant film can cover the top and part of the sidewall of the wafer under the guidance of the cutting force of the cutting head, so as to surround the front side of the wafer.

2. The wafer thinning method according to claim 1, characterized in that, The step of attaching the acid-resistant film to the front side of the wafer includes: The acid-resistant base layer is bonded to the front side of the wafer via the adhesive layer.

3. The wafer thinning method according to claim 2, characterized in that, The acid-resistant base layer is made of polyolefin copolymer.

4. The wafer thinning method according to claim 2, characterized in that, The thickness of the acid-resistant base layer is greater than or equal to 90 μm; and / or The thickness of the adhesive layer is greater than or equal to 30 μm.

5. The wafer thinning method according to any one of claims 1-4, characterized in that, The step of attaching the acid-resistant film to the front side of the wafer includes: The acid-resistant film is pressed onto the front side of the wafer using rollers.

6. The wafer thinning method according to any one of claims 1-4, characterized in that, The planarization process of the back side of the wafer using an etching solution includes: The wafer is immersed in the etching solution and left to stand for a first preset time to planarize the back side of the wafer. The etching solution includes hydrofluoric acid, sulfuric acid, and nitric acid.

7. The wafer thinning method according to claim 6, characterized in that, The first preset time is less than or equal to 3 minutes.

8. The wafer thinning method according to any one of claims 1-4, characterized in that, The method of planarizing the back side of the wafer using an etching solution further includes: The wafer is cleaned using pure water at a preset temperature.

9. The wafer thinning method according to claim 8, characterized in that, The preset water temperature is less than or equal to 50°C.

10. The wafer thinning method according to claim 8, characterized in that, The cleaning time for the wafer shall not exceed 6 minutes.

11. The wafer thinning method according to claim 8, characterized in that, The etching solution includes an acidic solution with oxidizing properties; After cleaning the wafer with pure water at a preset temperature, the process further includes: Remove the oxide film layer on the back side of the wafer.

12. The wafer thinning method according to claim 11, characterized in that, The removal of the oxide film layer on the back side of the wafer includes: The wafer is immersed in hydrofluoric acid solution and left to stand for a second preset time to remove the oxide film layer on the back side of the wafer. The second preset time is less than or equal to 3 minutes.

13. The wafer thinning method according to claim 12, characterized in that, The process of removing the oxide film layer on the back side of the wafer further includes: The wafer is cleaned at least once with pure water at a preset temperature; The wafer is dried. The acid-resistant film is removed from the wafer.

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