A water-soluble protective film, a method for preparing the same, and an application thereof

Abstract

The application relates to the technical field of semiconductor manufacturing, in particular to a water-soluble protective film and a preparation method and application thereof; the water-soluble protective film is prepared from raw materials comprising the following components: 2wt%-8wt% of a film forming agent; 0.05wt%-0.5wt% of a fluoride removing agent; 0.05wt%-0.5wt% of a buffer; and the balance of a solvent; the fluoride removing agent comprises ammonium tetraborate and / or ammonium gluconate. Compared with the prior art, the water-soluble protective film is prepared from raw materials comprising specific components, the components realize good mutual interaction under specific proportioning conditions, the water-soluble protective film can complex and absorb Al surface F ‑ under certain conditions, and can physically isolate water vapor, so that corrosion of the Al surface is effectively avoided; meanwhile, the water-soluble protective film is soluble in water and can be removed through water washing operation, the operation is simple, and the cost is low.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and more specifically, to a water-soluble protective film, its preparation method, and its application. Background Technology

[0002] In integrated circuits, copper (Cu) is a widely used metal interconnect material, and it is also used in components such as chip packaging pads and heat dissipation structures. Its core advantages are high conductivity and low resistivity, which can significantly improve chip performance and reduce power consumption. However, Cu is a soft metal and is easily oxidized in air to form a loosely structured CuO, which does not form a protective layer. Therefore, aluminum (Al) is used as the top layer metal.

[0003] Integrated circuit chip pads are typically made of aluminum (Al) and serve as the interface between the integrated circuit and the outside world. They are primarily used to achieve electrical connections and mechanical fixation between component pins, wires, and the substrate. Currently, in the traditional manufacturing process of aluminum pads, the passivation process is completed, and the Al pad is considered OK, meaning it meets the requirements. However, after being shipped to the packaging and testing plant, the Al surface will be corroded, and the longer the shipping time, the more severe the corrosion. Summary of the Invention

[0004] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. Therefore, the present invention provides a water-soluble protective film, its preparation method, and its application. The water-soluble protective film provided by the present invention can complex and absorb F on the Al surface. - Furthermore, it can physically isolate water vapor under certain conditions, thereby effectively preventing corrosion of the Al surface; at the same time, this water-soluble protective film is soluble in water and can be removed by water washing, which is simple to operate and low in cost.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0006] According to one aspect of the present invention, a water-soluble protective film is provided, prepared from raw materials comprising the following components:

[0007] Film-forming agent 2wt%~8wt%;

[0008] Defluorinating agent 0.05wt%~0.5wt%;

[0009] Buffer 0.05wt%~0.5wt%;

[0010] The remaining solvent;

[0011] The defluorinating agent includes ammonium tetraborate and / or ammonium gluconate.

[0012] In some embodiments, the film-forming agent includes one or more of polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol.

[0013] In some of these embodiments, the solvent is water.

[0014] In some of these embodiments, the buffer includes ammonium citrate and / or ammonium acetate.

[0015] In some embodiments, the water-soluble protective film is prepared from raw materials containing the following components:

[0016] Film-forming agent 4wt%~6wt%;

[0017] Defluorinating agent 0.1wt%~0.5wt%;

[0018] Buffer 0.05wt%~0.2wt%;

[0019] Solvent content: 93.3 wt% to 95.85 wt%.

[0020] In some embodiments, the thickness of the water-soluble protective film is 0.4 μm to 1 μm.

[0021] According to another aspect of the present invention, the present invention also provides a method for preparing the water-soluble protective film described in the above technical solution, comprising the following steps:

[0022] a) Mix the film-forming agent, defluorinating agent, buffer, and solvent, and react to obtain a hydrogel;

[0023] b) Coat the water-soluble gel obtained in step a) onto the wafer surface, and after curing, obtain a water-soluble protective film.

[0024] In some embodiments, step a) specifically includes the following steps: adding a first amount of solvent to a reaction apparatus, adding a film-forming agent while stirring at 45°C to 55°C and 100 rpm to 500 rpm, stirring for 4 to 6 hours, then cooling to 35°C to 40°C, adding a defluorinating agent, stirring for 20 to 30 minutes, then cooling to 25°C to 30°C, adding a buffer, stirring for 20 to 30 minutes until the solution is clear, finally adding the remaining solvent, and stirring at room temperature for 1 to 2 hours to complete the mixing process; the first amount of solvent accounts for 60% to 80% of the total mass of the solvent.

[0025] In some of these embodiments, in step a), the reaction is carried out under sealed conditions, at a temperature of 15°C to 35°C, for a time of 12 to 24 hours.

[0026] In some embodiments, step b) specifically includes: statically dropping 1 ml to 10 ml of the water-soluble gel onto the wafer surface, spreading it by rotating at 400 rpm to 600 rpm for 2 to 10 seconds, and then homogenizing the gel at 1200 rpm to 1800 rpm for 10 to 50 seconds to complete the coating process.

[0027] In some of these embodiments, in step b), the curing temperature is 60°C to 80°C and the time is 50s to 150s.

[0028] According to another aspect of the present invention, the present invention also provides a method for corrosion protection of aluminum pads, comprising the following steps:

[0029] After the aluminum pad passivation process is completed, a water-soluble protective film is formed on the wafer surface to prevent corrosion of the aluminum pads; the water-soluble protective film is the water-soluble protective film described in the above technical solution or the water-soluble protective film prepared by the preparation method described in the above technical solution.

[0030] In some embodiments, the method for preventing corrosion of the aluminum pads further includes:

[0031] Before the wafer undergoes packaging and testing, the water-soluble protective film is removed; the removal process specifically includes:

[0032] After rinsing with water at 25℃~50℃ for 1min~4min, wash with isopropanol at 20℃~30℃ for 0.5min~1.5min, and finally purge with N2 until the wafer surface is dried to complete the removal process.

[0033] Implementing the technical solution of the present invention has at least the following beneficial effects:

[0034] 1. The water-soluble protective film provided by this invention is prepared from raw materials containing specific amounts of components. Under specific mixing conditions, the components achieve good overall interaction, and the resulting water-soluble protective film can complex and absorb F on the Al surface. - Furthermore, under certain conditions (when the relative humidity is <60%, the water-soluble protective film is not affected by water vapor), it can physically isolate water vapor, thereby effectively preventing the Al surface from being corroded; at the same time, the water-soluble protective film is soluble in water and can be removed by water washing, which is simple to operate and low in cost.

[0035] 2. The preparation method provided by the present invention can form a water-soluble protective film on the wafer surface through spin coating and curing processes. The process is simple, the conditions are mild and easy to control, and only water is used as a solvent, avoiding the use of organic solvents. It is safer and more environmentally friendly and has broad application prospects.

[0036] 3. The water-soluble protective film provided by the present invention is particularly suitable for corrosion protection of aluminum pads. After the passivation process of aluminum pads is completed, a water-soluble protective film is formed on the wafer surface to effectively prevent corrosion of the Al surface. When the wafer needs to be packaged and tested, the water-soluble protective film can be completely removed by further steps such as washing and drying without any adverse effects.

[0037] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0038] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0039] Figure 1 This is a schematic diagram of Al corrosion on aluminum pads in the prior art.

[0040] Figure 2 The overall process flow diagram of the method for preventing corrosion of aluminum pads provided by the present invention.

[0041] Figure 3 This is a SEM image of the uncorroded Al pad surface provided in Embodiment 1 of the present invention.

[0042] Figure 4 This is a SEM image of the corroded Al pad surface.

[0043] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0044] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0045] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0046] In the description of this application, "same chemical composition" should be interpreted broadly, that is, the main components of the two have the same chemical composition, or the two have substantially the same chemical composition, but may have errors or impurities within the acceptable range that can be understood by those skilled in the art.

[0047] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0048] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0049] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0050] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0051] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0052] Currently, integrated circuit chip pads are typically made of aluminum (Al) pads. These serve as the interface between the integrated circuit and the external environment, primarily used for electrical connections and mechanical fixation between component pins, wires, and the substrate. In the traditional aluminum pad manufacturing process, the Al pad is considered OK after the passivation process. However, after being shipped to the packaging and testing plant, the Al surface becomes corroded, and the corrosion worsens with longer shipping times. This invention, through in-depth research, has discovered that the main cause of Al corrosion is the continuous corrosion of Al by halogen elements under humid conditions. (See [link to relevant documentation]). Figure 1 As shown, the reaction principle is as shown in equations (I) to (II):

[0053] AlF3+3H2O→Al(OH)3+3HF (I);

[0054] 6HF+2Al→2AlF3+3H2 (II).

[0055] Based on this, the present invention forms a water-soluble protective film on the wafer surface after the passivation process by spin coating and curing. This water-soluble protective film can complex and absorb F on the Al surface. - Furthermore, after curing into a film, it can physically isolate moisture under certain conditions (relative humidity <60%), preventing Al corrosion. When the wafer needs to be packaged and tested, the water-soluble protective film can be removed by washing and drying. This yields a water-soluble protective film, its preparation method, and its application to solve the above technical problems. Specifically, the present invention adopts the following technical solution:

[0056] According to one aspect of the present invention, a water-soluble protective film is provided, prepared from raw materials comprising the following components:

[0057] Film-forming agent 2wt%~8wt%;

[0058] Defluorinating agent 0.05wt%~0.5wt%;

[0059] Buffer 0.05wt%~0.5wt%;

[0060] The remaining solvent;

[0061] The defluorinating agent includes ammonium tetraborate and / or ammonium gluconate.

[0062] In this invention, the water-soluble protective film is prepared from raw materials including a film-forming agent, a defluorinating agent, a buffer, and a solvent, preferably from the same components. Under specific formulation conditions, these components achieve good overall interaction. The main function of the film-forming agent is to form a physical barrier with the solvent, isolating water vapor in environments with relative humidity <60%, thereby obtaining a water-soluble protective film and ensuring that the film is not damaged by water vapor in the air during actual use, thus meeting its protective requirements. The main function of the defluorinating agent is to provide a weakly alkaline (pH=8~9) solution for dissolving AlF3 and complexing F... - Furthermore, it will not corrode Al; the main function of the buffer is to reduce the crystallization temperature of the defluorinating agent (such as ammonium tetraborate) and ensure that the pH of the system is stable and less than 9; the above functional components, the defluorinating agent and the buffer, can work synergistically in the reaction system of the film-forming agent and the solvent to finally obtain a water-soluble protective film that meets the performance requirements of the present invention.

[0063] In a specific embodiment of the present invention, the film-forming agent, as the name suggests, has a film-forming effect. Specifically, it is a water-soluble polymeric film-forming agent, which plays a key role in the formation of a water-soluble protective film. It can form a physical barrier, isolating water vapor under ambient relative humidity <60%, thus meeting the protection requirements. In the present invention, the film-forming agent preferably includes one or more of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and polyethylene glycol (PEG), more preferably polyvinylpyrrolidone (PVP). The present invention does not have any special restrictions on the source of the film-forming agent; commercially available products or homemade products of the above-mentioned water-soluble polymeric materials well known to those skilled in the art can be used.

[0064] In a specific embodiment of the present invention, the raw material components for preparing the water-soluble protective film include 2wt% to 8wt% of a film-forming agent, specifically 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, or any value between the above two, preferably 4wt% to 6wt%. If the content of the film-forming agent is too low, the film layer will be thin, affecting its ability to isolate water vapor and remove sulfur. If it is too high, the film layer will be thick. Although this can improve the ability to isolate water vapor and remove sulfur to some extent, it is very detrimental to the subsequent water washing process. Considering all factors, the above-mentioned suitable dosage range yields the best overall performance.

[0065] The present invention selects the above-mentioned suitable types of film-forming agents and limits the appropriate content of film-forming agents, which is beneficial to obtaining a water-soluble protective film with stable structure and meeting the performance requirements of the present invention; without the film-forming agents, film cannot be formed.

[0066] In a specific embodiment of the present invention, the main function of the defluorinating agent is to provide a weakly alkaline (pH=8~9) solution for dissolving AlF3 and complexing F. - Furthermore, it does not corrode Al, and plays a crucial role in the anti-corrosion effect of the water-soluble protective film. In this invention, the defluorinating agent comprises ammonium tetraborate and / or ammonium gluconate, preferably ammonium tetraborate. Taking ammonium tetraborate as an example, in this invention, the defluorinating agent complexes and absorbs F... - The mechanism is as follows:

[0067] Ammonium tetraborate dissolves in water and ionizes to hydrolyze into H3BO3 and OH-. - F is absorbed through complexation via the following reaction. - :

[0068] AlF3+3OH - →Al(OH)3+3F - ;

[0069] H3BO3+4F - →BF4 - +3H2O.

[0070] The present invention does not impose any special restrictions on the source of the defluorinating agent; commercially available products well known to those skilled in the art can be used.

[0071] In a specific embodiment of the present invention, the raw material components for preparing the water-soluble protective film include 0.05wt% to 0.5wt% of a defluorinating agent, specifically 0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, or any value between the above two, preferably 0.1wt% to 0.5wt%. If the amount of defluorinating agent is too high, the pH increases, and the alkalinity becomes too strong, which will damage the passivation layer on the Al surface and cause alkaline corrosion. Although the defluorinating agent has a strong F removal ability, it damages the substrate, significantly increasing the risk of Al corrosion. If the amount is too low, it is not conducive to the defluorinating agent exerting its function. In addition, when the defluorinating agent is missing, the system lacks an alkaline buffer, cannot dissociate AlF3, and cannot complex F with boric acid. - F - Residue leads to electrochemical corrosion. Therefore, the present invention selects the above-mentioned suitable range of defluorinating agent content, which yields the best overall effect.

[0072] In a specific embodiment of the present invention, the main function of the buffer is to lower the crystallization temperature of the defluorinating agent (such as ammonium tetraborate), ensuring that the pH of the system is stable and less than 9, thereby avoiding excessive alkalinity due to excessive pH, which could lead to alkaline corrosion and damage to the substrate. In the present invention, the buffer preferably includes ammonium citrate and / or ammonium acetate, more preferably ammonium citrate. Taking ammonium citrate as an example, the mechanism of pH buffering by the buffer is as follows:

[0073] (NH4)3C6H5O7→3NH4 + +C6H5O7 3- ;

[0074] C6H5O7 3- +H₂O→HC₆H₅O₇ 2- +OH - ;

[0075] NH4 + →NH3+H + (Neutralizing OH- in an alkaline system) - ).

[0076] This invention has found that a dense aluminum oxide (Al2O3) passivation film forms on the surface of aluminum between pH 4 and 9. This film can prevent further corrosion, so aluminum is most stable in the above pH range.

[0077] The present invention does not impose any special restrictions on the source of the buffer, and commercially available or self-made organic carboxylic acid ammonium salt compounds known to those skilled in the art can be used.

[0078] In a specific embodiment of the present invention, the raw material components for preparing the water-soluble protective film include 0.05wt% to 0.5wt% of a buffer, specifically: 0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, or any value between the above two, preferably 0.05wt% to 0.2wt%. It should be noted that when the buffer is lacking, ammonium tetraborate crystals may precipitate in the solution, resulting in an incomplete film layer; simultaneously, the pH buffering capacity is weak, and localized areas may become overly alkaline, causing Al corrosion.

[0079] The present invention selects the above-mentioned suitable types of buffers and limits the appropriate buffer content, which is conducive to achieving better overall results, thereby further obtaining a water-soluble protective film that meets the performance requirements of the present invention.

[0080] In a specific embodiment of the present invention, the solvent mainly serves to dissolve the aforementioned raw material components, and also evaporates to form a film after coating, which can subsequently be used to remove the water-soluble protective film. In the present invention, the solvent is preferably water, and deionized water (DIW), which is well known to those skilled in the art, can be used.

[0081] In a specific embodiment of the present invention, the raw material components for preparing the water-soluble protective film include the remainder solvent, which, calculated as 100wt%, is specifically 91wt%~97.9wt%, preferably 93.3wt%~95.85wt%.

[0082] In a specific embodiment of the present invention, the thickness of the water-soluble protective film is preferably 0.4 μm to 1 μm, more preferably 0.6 μm to 0.8 μm. In this invention, the thickness of the water-soluble protective film within the above range can achieve the desired anti-corrosion effect.

[0083] The water-soluble protective film provided by this invention is prepared from raw materials containing specific amounts of components. Under specific mixing conditions, the components achieve good overall interaction, and the resulting water-soluble protective film can complex and absorb F on the Al surface. - Furthermore, it can physically isolate water vapor under certain conditions, thereby effectively preventing corrosion of the Al surface; at the same time, this water-soluble protective film is soluble in water and can be removed by water washing, which is simple to operate and low in cost.

[0084] According to another aspect of the present invention, the present invention also provides a method for preparing the water-soluble protective film described in the above technical solution, comprising the following steps:

[0085] a) Mix the film-forming agent, defluorinating agent, buffer, and solvent, and react to obtain a hydrogel;

[0086] b) Coat the water-soluble gel obtained in step a) onto the wafer surface, and after curing, obtain a water-soluble protective film.

[0087] This invention first involves mixing a film-forming agent, a defluorinating agent, a buffer, and a solvent, and then reacting them to obtain a hydrogel. In this invention, the film-forming agent, defluorinating agent, buffer, and solvent are the same as those in the aforementioned technical solutions, and will not be repeated here.

[0088] In a specific embodiment of the present invention, the mixing process preferably includes: adding a first amount of solvent to a reaction apparatus, adding a film-forming agent while stirring at 45°C to 55°C and 100 rpm to 500 rpm, stirring for 4 h to 6 h, then cooling to 35°C to 40°C, adding a defluorinating agent, stirring for 20 min to 30 min, then cooling to 25°C to 30°C, adding a buffer, stirring for 20 min to 30 min until the solution is clear, and finally adding the remaining solvent and stirring at room temperature for 1 h to 2 h to complete the mixing process;

[0089] More preferably:

[0090] The first amount of solvent is added to the reaction apparatus. The film-forming agent is added while stirring at 50°C and 200-400 rpm. The mixture is stirred for 4.5-5.5 hours. The temperature is then lowered to 40°C, and the defluorinating agent is added. The mixture is stirred for 20-30 minutes. The temperature is then lowered to 30°C, and the buffer is added. The mixture is stirred for 20-30 minutes until the solution is clear. Finally, the remaining solvent is added, and the mixture is stirred at 25°C for 1-2 hours to complete the mixing process.

[0091] The present invention employs the above-mentioned specific mixing process, which ensures that the components are fully mixed, facilitating subsequent reactions. At the same time, the present invention does not impose any special restrictions on the reaction apparatus used in the mixing process, as long as it can carry out subsequent sealed reactions. In a preferred embodiment of the present invention, the reaction apparatus is a reaction flask.

[0092] In a specific embodiment of the present invention, the solvent used in the first amount preferably accounts for 60% to 80% of the total mass of the solvent, specifically it can be 60%, 65%, 70%, 75%, 80%, or any value between the above two.

[0093] After completing the above mixing process, the present invention reacts the resulting mixture to obtain a hydrosoluble gel. The reaction is preferably carried out under sealed conditions, using a static curing technique. The reaction temperature is preferably 15℃~35℃, specifically 15℃, 20℃, 25℃, 30℃, 35℃, or any value between two of these. The reaction time is preferably 12h~24h, specifically 12h, 14h, 16h, 18h, 20h, 22h, 24h, or any value between two of these. The present invention, using the reaction process defined by the above conditions and parameters, can ensure the acquisition of a hydrosoluble gel with the desired effect.

[0094] After obtaining the water-soluble gel, the present invention coats the obtained water-soluble gel onto the surface of a wafer, and after curing, obtains a water-soluble protective film. The present invention does not have any special limitations on the wafer; any conventional wafer known to those skilled in the art can be used. A chip region is formed on the wafer, the chip region including a circuit region and a pixel region. The circuit region is arranged around the pixel region, and transistors and aluminum pads are formed in the circuit region, with the aluminum pads surrounding the transistors.

[0095] In a specific embodiment of the present invention, the coating process preferably includes: statically dropping 1 ml to 10 ml of the water-soluble gel onto the wafer surface, spreading it by rotating at 400 rpm to 600 rpm for 2 to 10 seconds, and then uniformly coating it by rotating at 1200 rpm to 1800 rpm for 10 to 50 seconds to complete the coating process.

[0096] More preferably:

[0097] 5.5 ml to 6.5 ml of the hydrosoluble gel is statically dropped onto the wafer surface, spread by spinning at 450 rpm to 550 rpm for 4 to 6 seconds, and then homogenized at 1400 rpm to 1600 rpm for 20 to 40 seconds to complete the coating process. This invention uses the above spin-coating method to cover the hydrosoluble gel onto the wafer surface, ensuring the subsequent formation of a water-soluble protective film of uniform thickness.

[0098] In a specific embodiment of the present invention, the curing temperature is preferably 60℃~80℃, specifically 60℃, 65℃, 70℃, 75℃, 80℃, or any value between the two; the curing time is preferably 50s~150s, specifically 50s, 60s, 90s, 120s, 150s, or any value between the two. The curing process defined by the above conditions and parameters ensures sufficient solvent evaporation, forming a solid, continuous gel film, ultimately obtaining a water-soluble protective film with the desired effect.

[0099] The preparation method provided by this invention can form a water-soluble protective film on the wafer surface through spin coating and curing processes. The process is simple, the conditions are mild and easy to control, and only water is used as a solvent, avoiding the use of organic solvents. It is safer and more environmentally friendly and has broad application prospects.

[0100] According to another aspect of the present invention, the present invention also provides a method for corrosion protection of aluminum pads, comprising the following steps:

[0101] After the aluminum pad passivation process is completed, a water-soluble protective film is formed on the wafer surface to prevent corrosion of the aluminum pads; the water-soluble protective film is the water-soluble protective film described in the above technical solution or the water-soluble protective film prepared by the preparation method described in the above technical solution.

[0102] In this invention, the water-soluble protective film is the water-soluble protective film described in the above-mentioned technical solution or the water-soluble protective film prepared by the preparation method described in the above-mentioned technical solution. Based on this, the water-soluble protective film possesses all the features and advantages of the water-soluble protective film described in the above-mentioned technical solution, which will not be repeated here. In this invention, the overall process flow diagram of the aluminum pad corrosion prevention method can be found in [reference needed]. Figure 2 As shown, the process of forming a water-soluble protective film on the wafer surface is the same as the preparation method of the water-soluble protective film in the above technical solution, and will not be repeated here.

[0103] In a specific embodiment of the present invention, the method for preventing corrosion of the aluminum pads preferably further includes:

[0104] Before the wafer undergoes packaging and testing, the water-soluble protective film is removed. In a preferred embodiment of the present invention, the removal process specifically includes:

[0105] After rinsing with water at 25℃~50℃ for 1min~4min, the wafer is washed with isopropanol at 20℃~30℃ for 0.5min~1.5min, and finally purged with N2 until the wafer surface is dry, thus completing the removal process. In this invention, the water-soluble protective film is a water-soluble film, which can be dissolved in water through the above-mentioned water spray rinsing process, thereby achieving effective removal of the water-soluble protective film; simultaneously, the subsequent isopropanol washing process and N2 purging achieve wafer surface drying, ultimately obtaining the target product with the desired effect.

[0106] Therefore, the water-soluble protective film provided by the present invention is particularly suitable for corrosion protection of aluminum pads. After the passivation process of aluminum pads is completed, the formation of a water-soluble protective film on the wafer surface can effectively prevent Al surface corrosion. When the wafer needs to be packaged and tested, the water-soluble protective film can be completely removed by further steps such as washing and drying without any adverse effects.

[0107] The present application will be described in detail below with reference to the accompanying drawings and embodiments. However, the implementation and protection of the present invention are not limited thereto. The following embodiments are only some embodiments of the present application and are not intended to limit the present application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0108] Example 1

[0109] (1) Preparation of hydrosol gel: According to the mass ratio, 70wt% of the total amount of solvent (DIW) was weighed and added to the reaction flask. Under the conditions of continuous stirring at 300rpm and 50℃, an appropriate amount of film-forming agent (PVP) powder was slowly added and stirred for 5h. Then, under the condition of continuous stirring at 40℃, an appropriate amount of defluorinating agent (ammonium tetraborate) was slowly added and stirred for 25min. Then, under the condition of continuous stirring at 30℃, an appropriate amount of buffer (ammonium citrate) was added and stirred for 25min until the solution was clear. Finally, the remaining 30wt% of solvent (DIW) was added, the temperature was lowered to 25℃ and stirring was continued for 1.5h to obtain a homogeneous mixed solution. The reaction flask was sealed and allowed to stand and mature at 25℃ for 18h to obtain the hydrosol gel.

[0110] The proportions of the above substances are shown in Table 1 below.

[0111] (2) Preparation of water-soluble protective film: 5.5~6.5 ml of the water-soluble gel obtained in step (1) is statically dropped onto the surface of the wafer to be treated, spread by rotating at 500 rpm for 5 s, and homogenized at 1500 rpm for 30 s to coat the water-soluble gel onto the wafer surface; then it is cured on a clean hot plate at 70℃ for 110 s to allow the solvent to evaporate completely and form a solid, continuous gel film with a thickness of 0.6~0.8 μm, which is the target product water-soluble protective film.

[0112] (3) Application of water-soluble protective film: After the passivation process is completed, a water-soluble protective film is formed on the wafer surface through the above process. The protective effect is shown in Table 1 below. The results show that the water-soluble protective film provided in Example 1 of this invention can complex and remove F from the Al surface. - Furthermore, once cured into a film, it can physically isolate moisture under ambient relative humidity conditions of <60%, effectively preventing Al pad corrosion.

[0113] Before the wafer is sent to the packaging and testing plant for encapsulation, the water-soluble protective film can be removed. This water-soluble protective film is water-soluble and can be removed using the following dissolution process:

[0114] Rinse with a 40℃ DIW spray for 2.5 minutes.

[0115] Then, wash with IPA (isopropanol) at 25°C for 1 min.

[0116] Finally, the wafer was purged with N2 until the wafer surface was completely dry; the SEM image of the uncorroded Al pad surface provided in Example 1 of this invention is shown below. Figure 3 As shown; additionally, for comparison with the case without water-soluble protective film, the SEM image of the corroded Al pad surface is shown in [reference needed]. Figure 4 As shown.

[0117] Examples 2-5 and Comparative Examples 1-5

[0118] The water-soluble gel and the water-soluble protective film were obtained sequentially using the preparation method provided in Example 1, and the obtained water-soluble protective film was further applied according to step (3) of Example 1; the differences from Example 1 are shown in Table 1 below.

[0119] Table 1. Data on the selection and proportion of substances in the examples and comparative examples, and their protective effects.

[0120]

[0121] Note: In Table 1, "%" refers to mass percentage; Defect count is the number of Al etching points on the wafer surface scanned by KLA. The more points, the more severe the Al etching.

[0122] The comparison shows that the water-soluble protective films provided in Examples 1-5 of the present invention can complex and absorb F on the Al surface. - Furthermore, it can physically isolate water vapor under ambient relative humidity <60%, thereby effectively preventing Al surface corrosion. Simultaneously, this water-soluble protective film is soluble in water and can be removed by washing, making the operation simple and cost-effective. Example 1, in particular, effectively prevents Al pad corrosion. In Example 2, the content of each functional component is reduced, the film layer becomes thinner, the F removal ability is slightly lower, and the overall performance is slightly worse. In Example 3, the content of each functional component is increased, the film is thicker, the protection is better, and the F removal ability is stronger, but the viscosity is high, and the water dissolution process is slightly slower. Examples 4-5 use alternative components, and the overall effect is slightly lower than Example 1, but Examples 2-5 can still achieve the effect of preventing Al pad corrosion. Comparative Example 1 lacks the key component defluorinating agent, the system has no alkaline buffer, cannot dissociate AlF3, and cannot complex F with boric acid. - F -Residues lead to electrochemical corrosion; Comparative Example 2 lacks a buffer, and ammonium tetraborate crystals may precipitate in the solution, resulting in an incomplete film, weak pH buffering capacity, and potential localized over-alkalinity; Comparative Example 3 lacks a film-forming agent and cannot form a film; Comparative Example 4 uses an unsuitable solvent, PGMEA, as PVP is insoluble in PGMEA, and salts such as ammonium tetraborate also cannot be dissolved, thus preventing film formation; Comparative Example 5, due to excessive defluorinating agent, increases pH, significantly increasing the risk of Al corrosion.

[0123] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0124] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0125] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-soluble protective film, characterized in that, It is prepared from the following raw materials: Film-forming agent 2wt%~8wt%; Defluorinating agent 0.05wt%~0.5wt%; Buffer 0.05wt%~0.5wt%; The remaining solvent; The film-forming agent is polyvinylpyrrolidone; the defluorinating agent includes ammonium tetraborate and / or ammonium gluconate; the buffer includes ammonium citrate and / or ammonium acetate.

2. The water-soluble protective film according to claim 1, characterized in that, The solvent is water.

3. The water-soluble protective film according to claim 1, characterized in that, The water-soluble protective film is prepared from the following raw materials: Film-forming agent 4wt%~6wt%; Defluorinating agent 0.1wt%~0.5wt%; Buffer 0.05wt%~0.2wt%; Solvent content: 93.3 wt% to 95.85 wt%.

4. The water-soluble protective film according to claim 1, characterized in that, The thickness of the water-soluble protective film is 0.4 μm to 1 μm.

5. A method for preparing a water-soluble protective film according to any one of claims 1 to 4, characterized in that, Includes the following steps: a) Mix the film-forming agent, defluorinating agent, buffer, and solvent, and react to obtain a hydrogel; b) Coat the water-soluble gel obtained in step a) onto the wafer surface, and after curing, obtain a water-soluble protective film.

6. The preparation method according to claim 5, characterized in that, In step a): The mixing process specifically includes: adding a first amount of solvent to the reaction apparatus, adding a film-forming agent while stirring at 45℃~55℃ and 100rpm~500rpm, stirring for 4h~6h, then cooling to 35℃~40℃, adding a defluorinating agent, stirring for 20min~30min, then cooling to 25℃~30℃, adding a buffer, stirring for 20min~30min until the solution is clear, and finally adding the remaining solvent, stirring at room temperature for 1h~2h to complete the mixing process; the first amount of solvent accounts for 60%~80% of the total mass of the solvent; and / or, The reaction is carried out under sealed conditions, at a temperature of 15℃ to 35℃, for a time of 12h to 24h.

7. The preparation method according to claim 5, characterized in that, In step b): The coating process specifically includes: statically dropping 1 ml to 10 ml of the aqueous gel onto the wafer surface, spreading it by rotating at 400 rpm to 600 rpm for 2 to 10 seconds, and then homogenizing the gel at 1200 rpm to 1800 rpm for 10 to 50 seconds to complete the coating process; and / or, The curing temperature is 60℃~80℃, and the time is 50s~150s.

8. A method for preventing corrosion of aluminum solder pads, characterized in that, Includes the following steps: After the aluminum pad passivation process is completed, a water-soluble protective film is formed on the wafer surface to prevent corrosion of the aluminum pads; the water-soluble protective film is the water-soluble protective film according to any one of claims 1 to 4 or the water-soluble protective film prepared by the preparation method according to any one of claims 5 to 7.

9. The method for corrosion protection of aluminum pads according to claim 8, characterized in that, Also includes: The water-soluble protective film is removed before the wafer is packaged and tested. The removal process specifically includes: After rinsing with water at 25℃~50℃ for 1min~4min, wash with isopropanol at 20℃~30℃ for 0.5min~1.5min, and finally purge with N2 until the wafer surface is dried to complete the removal process.

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