Silicon carbide MOS device chemical plating grid electrode protection method and process structure

Abstract

The invention provides a silicon carbide MOS device chemical plating grid electrode protection method and a process structure, and the protection method comprises the steps: enabling a contact surface of a printing net to be pasted on a target wafer, enabling the position of a mesh to correspond to the position of a grid electrode bonding pad, enabling a net body to accurately cover a region of a source electrode bonding pad, enabling a protection glue to be accurately coated on a designated region instead of the whole surface of the target wafer, and enabling the surface of the target wafer to be protected. Therefore, the use amount of the protective glue is effectively saved and cost is reduced. After gluing is completed, a protective glue layer with a stable structure is formed on the surface of the grid bonding pad through a light curing process, and the protective layer has the peelable characteristic while keeping good adhesive force. And after the chemical plating treatment of the source electrode bonding pad is completed, the protection glue layer can be completely removed without residual pollutants, so that the reliable protection of the grid electrode bonding pad is realized. According to the chemical plating grid protection method for the silicon carbide MOS device, the protection effect and the process stability of the grid region in the chemical plating process are improved by optimizing the selection of the protection material and the coating process.

Description

Technical Field

[0001] The present application belongs to the field of semiconductor manufacturing technology, and more specifically, relates to a method and process structure for protecting a gate electrodeposited in a silicon carbide MOS device. Background Art

[0002] Silicon carbide (SiC) MOS device module packaging typically requires the source pad to be solderable, while the gate pad must retain an aluminum surface for aluminum wire bonding. To this end, electroless nickel-palladium-gold plating is widely used for source metallization of SiC devices. However, to achieve aluminum wire bonding on the gate pad, the gate area must be protected during the electroless plating process to prevent its surface from being covered by the plating layer.

[0003] Currently, photoresist masking is commonly used. By coating the gate pad with photoresist, only the source region is exposed for nickel-palladium-gold plating. While this process enables selective metallization, it involves multiple equipment steps, including coaters, exposure machines, developers, and strippers. This makes the process complex and presents numerous challenges. First, photoresist materials are expensive and chemically unstable. While they are reasonably acid-resistant, they struggle to withstand strong alkaline environments. Chemical plating solutions are typically highly alkaline, which can easily cause the photoresist to dissolve or even peel, severely impacting process reliability. Second, the stripping solution used in the stripping process is susceptible to degradation due to humidity, resulting in a short lifespan. Furthermore, the photoresist removal process generates micron-sized adhesive debris, which adheres to the wafer surface, forming stubborn residues and making cleaning more difficult. Furthermore, in thin-wafer electroless plating processes, the stripping solution can erode and dissolve the protective film on the wafer's backside during the stripping phase, further complicating process control. These issues not only increase production costs and process risks, but can also negatively impact device performance and yield. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a method and process structure for protecting the gate of a silicon carbide MOS device during chemical plating, so as to solve the technical problem of gate protection of silicon carbide MOS devices during chemical plating in the prior art.

[0005] To achieve the above objectives, the technical solution adopted in this application is:

[0006] A method for protecting a silicon carbide MOS device by chemical plating gate is provided, comprising the following steps:

[0007] Gluing: Place the contact surface of the printed mesh on the target wafer so that the mesh position corresponds to the position of the gate pad and the mesh body covers the source pad; apply protective glue on the glued surface of the printed mesh so that the gate pad is coated with protective glue;

[0008] Curing the protective glue: Remove the printed screen and use curing light to irradiate the protective glue on the target wafer to form a cured protective glue layer on the gate pad;

[0009] Removal of adhesive after chemical plating: After chemical plating on the source pad of the target wafer, the protective adhesive layer on the gate pad is peeled off.

[0010] As a further improvement of the above technical solution:

[0011] Optionally, the printing mesh is an electroformed steel mesh, and an anti-wear coating is provided on the contact surface of the electroformed steel mesh.

[0012] Optionally, the printed screen is a silk screen, the mesh of the silk screen covers the source pad, and the area outside the source pad on the target wafer is exposed under the mesh of the silk screen.

[0013] Optionally, after chemically plating the source pad of the target wafer, the target wafer is immersed in a degumming solution to cause the protective adhesive layer to fall off as a whole, thereby peeling off the protective adhesive layer on the gate pad.

[0014] Optionally, the target wafer is immersed in the degumming solution for a time period ranging from 5 minutes to 10 minutes.

[0015] Optionally, after chemically plating the source pad of the target wafer, an adhesive film is applied to the target wafer so that the protective adhesive layer adheres to the adhesive film, and then the adhesive film is torn off to peel off the protective adhesive layer on the gate pad.

[0016] Optionally, the viscosity of the protective glue ranges from 13000 cps to 15000 cps.

[0017] Optionally, the thickness of the protective adhesive layer ranges from 80um to 100um.

[0018] Optionally, the curing light is ultraviolet light with a wavelength range of 320nm-420nm, the curing energy range of the ultraviolet light is 4000mJ / cm2-5000mJ / cm2, and the curing time range is 5s-15s.

[0019] The present application also provides a process structure for protecting the electroless plating gate of a silicon carbide MOS device, comprising:

[0020] A printed screen having meshes and a mesh body, wherein the printed screen is attached to the target wafer, the positions of the meshes correspond to the positions of the gate pads, and the mesh body covers the source pads;

[0021] The protective glue is coated on the printing net and leaks onto the gate pad through the mesh. After the protective glue is cured, a protective glue layer is formed on the gate pad.

[0022] The beneficial effects of the chemical plating gate protection method for silicon carbide MOS devices provided in this application are:

[0023] The present application provides a method for chemically plating gate protection for silicon carbide MOS devices, which first covers the contact surface of the printed mesh on the target wafer so that the mesh position corresponds to the position of the gate pad, and the mesh body accurately covers the area of ​​the source pad, so that the protective glue is accurately coated on the specified area, rather than the entire target wafer surface, thereby effectively saving the amount of protective glue and reducing costs. After the glue is applied, a structurally stable protective glue layer is formed on the surface of the gate pad through a light curing process. The protective layer has a peelable property while maintaining good adhesion. After the source pad is chemically plated, the protective glue layer can be completely removed without residual contaminants, thereby achieving reliable protection of the gate pad. The present application's method for chemically plating gate protection for silicon carbide MOS devices improves the protection effect and process stability of the gate area during the chemical plating process by optimizing the selection of protective materials and the coating process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1 Flowchart of the chemically plated gate protection method for silicon carbide MOS devices provided in this application;

[0026] Figures 2 to 7 Schematic diagram of the structural change of the silicon carbide MOS device in the first gate protection method;

[0027] Figures 8 to 12 Schematic diagram of the structural changes of silicon carbide MOS devices in the second gate protection method.

[0028] Among them, the reference numerals in the figures are:

[0029] 1. Printing screen; 2. Target wafer;

[0030] 21. Gate pad; 22. Source pad;

[0031] 3. Protect the rubber layer. DETAILED DESCRIPTION

[0032] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0034] Furthermore, 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 the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0035] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0036] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0037] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of the present invention.

[0038] In the following description, suffixes such as “module,” “component,” “assembly,” or “unit” are used only to facilitate the description of the present invention and have no specific meanings. Therefore, they can be used interchangeably.

[0039] The present invention will be further described in detail below through specific embodiments with reference to the accompanying drawings.

[0040] In order to solve the problem of protecting the gate pad 21 of the silicon carbide (SiC) MOS device during the chemical plating process of the source pad 22, as shown in FIG. Figures 3 to 5 、 Figure 9 and Figure 10 As shown, the present application provides a process structure for protecting the electroless plating gate of a silicon carbide MOS device, including a printing screen 1 and a protective glue.

[0041] Among them, the printing mesh 1 can specifically be an electroformed steel mesh or a silk screen. The printing mesh 1 is precisely aligned and then affixed to the surface of the target wafer 2, wherein the position of the mesh strictly corresponds to the position of the gate pad 21, and the mesh body completely covers the source pad 22 area. The protective glue should be a polyurethane acrylate UV glue, which is evenly applied to the upper surface of the printing mesh 1 by scraper coating. The protective glue leaks through the mesh to the surface of the gate pad 21. After removing the printing mesh 1, it is cured by UV light to form a protective glue layer 3. Due to the shielding effect of the mesh body, the protective glue will not contact the surface of the source pad 22. During chemical plating, the plating solution can only react with the exposed source pad 22, thereby effectively avoiding the gate pad 21 from being affected by the chemical plating process. This process structure achieves precise protection of the gate pad 21 by physical shielding.

[0042] like Figure 1As shown, the present application also provides a method for chemically plating gate protection of silicon carbide MOS devices. This method requires that the contact surface of the printed screen 1 be attached to the target wafer 2 so that the mesh position corresponds to the position of the gate pad 21, and the mesh body covers the source pad 22. Among them, the mesh size of the printed screen 1 must match the geometric parameters of the gate pad 21 on the target wafer 2 to ensure that the mesh and the gate pad 21 are accurately aligned when the printed screen 1 is attached, and at the same time, the mesh body accurately covers the area of ​​the source pad 22, so that the protective glue is accurately coated on the specified area, rather than the entire target wafer 2 surface, thereby effectively saving the amount of protective glue and reducing costs. The printed screen 1 can be customized according to the position and size of the gate pad 21 and the source pad 22, or an existing printed screen that meets the working requirements can be selected. When applying the glue, the protective glue specifically uses a polyurethane acrylate UV glue that is resistant to chemical plating solutions. This material is applied to the surface of the gate pad 21 through the mesh structure of the printing screen 1. Its molecular structure characteristics enable it to effectively resist the erosion of the plating solution in the subsequent chemical plating process, avoiding the swelling or decomposition problems that are prone to occur in conventional UV glue. The glue coating equipment can use an existing printing press, and the glue coating tool can use a scraper made of natural rubber or synthetic rubber with lower hardness to avoid the generation of metal debris during the printing process. After the glue is applied, a structurally stable protective glue layer 3 is formed on the surface of the gate pad 21 through a light curing process. The protective layer has a peelable property while maintaining good adhesion. After the source pad 22 completes the chemical plating treatment, the protective glue layer 3 can be completely removed without residual contaminants, thereby achieving reliable protection of the gate pad 21. The silicon carbide MOS device chemical plating gate protection method of the present application improves the protection effect and process stability of the gate area during the chemical plating process by optimizing the selection of protective materials and the coating process.

[0043] In a specific embodiment of the present application, the printing mesh 1 specifically uses an electroformed steel mesh as a mask substrate. The electroformed steel mesh is formed by an electrochemical deposition process, and its mesh size tolerance is controlled within the range of ±5μm, which can directly match the design size of the gate pad 21 without the need for additional aperture compensation or hole wall finishing. In order to reduce the risk of mechanical damage during the contact between the mask and the target wafer 2, a certain thickness of anti-wear coating is provided on the surface of the electroformed steel mesh in contact with the target wafer 2. The anti-wear coating can specifically be a polyurethane nanocoating. While maintaining the accuracy of the mesh structure, the contact friction coefficient can also be reduced, effectively avoiding the problem of scratches on the target wafer surface that may be caused by traditional steel meshes during contact printing. When using an electroformed steel mesh, the UV glue is only filled into the gate pad 21 corresponding to each mesh, thereby reducing the material loss caused by the UV glue flowing to other areas.

[0044] In another specific embodiment of the present application, the printed screen 1 can be an alternative to a silk screen. When installing, the silk screen ensures that its mesh completely covers the source pad 22 area on the target wafer 2, while exposing the gate pad 21 and other non-plated areas under the mesh structure of the silk screen. When UV glue is applied, the glue is evenly filled into the gate pad 21 and the surrounding non-plated areas through the mesh of the silk screen to form a continuous protective film layer, so that the UV glue can completely cover all non-plated areas that need to be protected, which not only improves the consistency of the protection effect, but also makes the cured protective film layer have integrity, which is convenient for subsequent manual tearing off in one go, while ensuring the protection effect and simplifying the subsequent glue removal process.

[0045] In a specific embodiment of the present application, after the source pad 22 of the target wafer 2 is subjected to chemical plating, an isopropylamine (IPA) solution is used as a stripping medium to remove the protective adhesive layer 3. The IPA solution can penetrate into the interface between the protective adhesive layer 3 and the gate pad 21, causing the polyurethane acrylate UV adhesive to swell and reduce its adhesion, ultimately achieving the stripping of the protective adhesive layer 3 from the surface of the gate pad 21. This method avoids the surface damage that may be caused by mechanical stripping. At the same time, the IPA solution has no corrosive effect on the already formed chemical plating layer, ensuring that the plating quality of the source pad 22 is not affected. IPA solution debonding is suitable for debonding after electroforming steel mesh coating and silk screen coating.

[0046] In a specific embodiment of the present application, the target wafer 2 is immersed in the isopropylamine solution for a time range of 5 minutes to 10 minutes, which ensures that the protective adhesive layer 3 can fully swell and completely detach from the surface of the gate pad 21, while avoiding unnecessary impact of the solution on other functional areas of the target wafer 2 due to excessively long immersion time.

[0047] In another specific embodiment of the present application, after the source pad 22 of the target wafer 2 is chemically plated, an adhesive film can also be applied to the target wafer 2 to remove the protective adhesive layer 3 by mechanical stripping. The adhesive film is applied flatly to the surface of the target wafer 2 to ensure that the adhesive film is in full contact with the protective adhesive layer 3 and forms an effective bond. The adhesive film is then torn off at a uniform speed at a peeling angle of 45°-90°, and the protective adhesive layer 3 is completely peeled off from the surface of the gate pad 21 using the adhesion of the adhesive film. The mechanical stripping process does not require the use of chemical solvents, which avoids the possible impact of solvents on other functional areas on the surface of the target wafer 2, and also simplifies the subsequent cleaning process. The film is more suitable for removing glue after the electroformed steel mesh is coated with glue.

[0048] In a specific embodiment of the present application, the viscosity of the protective glue ranges from 13000 cps to 15000 cps.

[0049] In a specific embodiment of the present application, the thickness of the protective adhesive layer 3 is in the range of 80um-100um.

[0050] In a specific embodiment of the present application, the curing light is an ultraviolet light with a wavelength range of 320nm-420nm, and the curing energy range of the ultraviolet light is 4000mJ / cm 2 -5000mJ / cm 2 , the curing time range is 5s-15s.

[0051] like Figures 2 to 7 As shown, taking the electroformed steel mesh as an example, the specific steps and parameters of the electroless plating gate protection method for silicon carbide MOS devices are as follows:

[0052] S1. Glue application: An electroformed steel mesh with a mesh size corresponding to the size of the gate pad 21 to be protected is applied to the target wafer 2, with the mesh position corresponding to the position of the gate pad 21 and the mesh covering the source pad 22. A polyurethane acrylate UV adhesive is applied to the electroformed steel mesh with a viscosity controlled at 13,000 cps. The UV adhesive is applied to the gate pad 21 to be protected using a printer, with the thickness of the UV adhesive applied to the gate pad 21 being at least 80 μm.

[0053] S2. Curing protective glue: Remove the electroformed steel mesh and use a wavelength of 320nm and a curing energy range of 4000mJ / cm 2 Expose the UV glue to the gate pad 21 with ultraviolet light for at least 5 seconds to form a cured protective glue layer 3;

[0054] S3. Removal of adhesive after chemical plating: After chemical plating the source pad 22 of the target wafer 2, apply an adhesive film on the target wafer 2 and remove the protective adhesive layer 3 by mechanical peeling; alternatively, soak the target wafer 2 in IPA solution for at least 5 minutes to allow the protective adhesive layer 3 to fall off as a whole, and then rinse and dry with water.

[0055] like Figures 8 to 12 As shown, taking the silk screen as an example, the specific steps and parameters of the electroless plating gate protection method for silicon carbide MOS devices are as follows:

[0056] S1. Glue application: A silk screen with a mesh size corresponding to the size of the gate pad 21 to be protected is applied to the target wafer 2, so that the mesh covers the source pad 22 and the other non-plated areas are exposed under the mesh structure of the silk screen; a polyurethane acrylate UV glue is applied to the silk screen, and the viscosity of the UV glue is controlled at 15,000 cps; the UV glue is applied to the non-plated areas using a printer, and the thickness of the UV glue applied to the non-plated areas is at least 100 μm;

[0057] S2. Curing protective glue: remove the screen and use a wavelength of 420nm and a curing energy range of 5000mJ / cm 2 Expose the UV adhesive with ultraviolet light for at least 15 seconds to form a cured protective adhesive layer 3 on the non-plating area;

[0058] S3. Removal of adhesive after chemical plating: After chemical plating the source pad 22 of the target wafer 2, manually remove the protective adhesive layer 3 on the target wafer 2; alternatively, soak the target wafer 2 in IPA solution for at least 10 minutes to allow the protective adhesive layer 3 to fall off as a whole, and then rinse and dry with water.

[0059] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for protecting a silicon carbide MOS device by electroless plating gate, characterized in that: The steps include: Gluing: placing the contact surface of the printing mesh (1) on the target wafer (2) so that the mesh position corresponds to the position of the gate pad (21), and the mesh body covers the source pad (22); applying protective glue on the glue-coated surface of the printing mesh (1) so that the gate pad (21) is coated with the protective glue; Curing the protective glue: removing the printed screen (1) and irradiating the protective glue on the target wafer (2) with curing light to form a cured protective glue layer (3) on the gate pad (21); Removing adhesive after chemical plating: After chemical plating the source pad (22) of the target wafer (2), the protective adhesive layer (3) on the gate pad (21) is peeled off.

2. The method for protecting the gate of a silicon carbide MOS device by chemical plating according to claim 1, wherein: The printing screen (1) is an electroformed steel screen, and an anti-wear coating is provided on the contact surface of the electroformed steel screen.

3. The method for protecting the gate of a silicon carbide MOS device by chemical plating according to claim 1, wherein: The printing screen (1) is a silk screen, the mesh of the silk screen covers the source electrode pad (22), and the area outside the source electrode pad (22) on the target wafer (2) is exposed under the mesh of the silk screen.

4. The method for protecting the gate of a silicon carbide MOS device by chemical plating according to any one of claims 1 to 3, wherein: After chemical plating is performed on the source pad (22) of the target wafer (2), the target wafer (2) is immersed in a degumming solution to cause the protective adhesive layer (3) to fall off as a whole, thereby peeling off the protective adhesive layer (3) on the gate pad (21).

5. The method for protecting the gate of a silicon carbide MOS device by chemical plating according to claim 4, wherein: The target wafer (2) is immersed in the degumming solution for a time ranging from 5 minutes to 10 minutes.

6. The method for protecting the gate of a silicon carbide MOS device by chemical plating according to any one of claims 1 to 3, wherein: After chemical plating is performed on the source pad (22) of the target wafer (2), an adhesive film is applied to the target wafer (2), so that the protective adhesive layer (3) adheres to the adhesive film, and then the adhesive film is torn off, thereby peeling off the protective adhesive layer (3) on the gate pad (21).

7. The method for protecting the gate of a silicon carbide MOS device by chemical plating according to any one of claims 1 to 3, wherein: The viscosity of the protective glue ranges from 13000 cps to 15000 cps.

8. The method for protecting the gate of a silicon carbide MOS device by electroless plating according to any one of claims 1 to 3, wherein: The thickness of the protective adhesive layer (3) ranges from 80um to 100um.

9. The method for protecting the gate of a silicon carbide MOS device by electroless plating according to any one of claims 1 to 3, wherein: The curing light is an ultraviolet light with a wavelength range of 320nm-420nm, and the curing energy range of the ultraviolet light is 4000mJ / cm 2 -5000mJ / cm 2 , the curing time range is 5s-15s.

10. A process structure for protecting the electroless plating gate of a silicon carbide MOS device, characterized in that: include A printing screen (1) having meshes and a mesh body, wherein the printing screen (1) is attached to a target wafer (2), the positions of the meshes corresponding to the positions of the gate pads (21), and the mesh body covers the source pads (22); The protective glue is coated on the printing screen (1) and leaks through the mesh to the gate pad (21). After the protective glue is cured, a protective glue layer (3) is formed on the gate pad (21).

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