Double-sided silver fast recovery diode and preparation method thereof

Abstract

The invention discloses a double-sided silver fast recovery diode and a preparation method thereof, and relates to the technical field of semiconductors. The method comprises the steps that the front surface of a wafer is covered with a first anti-micro-corrosion metal layer, and main junction diffusion and terminal passivation are completed on the front surface of the wafer; covering the surface of the first anti-micro-corrosion metal layer with a second anti-micro-corrosion metal layer, and enabling the second anti-micro-corrosion metal layer to completely cover the front surface of the wafer; depositing front metal on the surface of the second anti-micro-corrosion metal layer; the front metal is corroded until the second anti-micro-corrosion metal layer is exposed, and the orthographic projection area of the front metal edge is smaller than the orthographic projection area of the first anti-micro-corrosion metal layer; corroding the second anti-micro-corrosion metal layer until a terminal passivation area is exposed; covering the surface of the terminal passivation area with a polyimide layer; and depositing back metal on the back of the wafer. According to the method, the interior of the passivation area of the terminal is not damaged, and the product yield and reliability of the double-sided silver fast recovery diode are improved.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a double-sided silver fast recovery diode and a preparation method thereof. Background Art

[0002] With the promotion and application of new energy, the requirements for charging and discharging power of power sources are getting higher and higher. For example, fast charging piles will use products with higher voltage and larger current to meet the high-power and high-speed charging needs. Therefore, the double-sided silver fast recovery diodes used in charging equipment such as charging piles also need higher current conduction capabilities.

[0003] In order to improve the current flow capacity of the double-sided silver fast recovery diode, the existing double-sided silver fast recovery diode is usually provided with a silver layer with good conductivity and heat dissipation on both sides thereof. In the existing method of preparing the silver layer on both sides of the double-sided silver fast recovery diode, the metal silver layer is usually directly provided on the main junction area of ​​the wafer, and the polyimide layer that plays a passivation protection role is usually coated on the surface of the silver layer. Due to the poor adhesion between the polyimide layer and the silver layer, the polyimide layer is easily caused to peel off; at the same time, when the metal silver layer provided in the terminal passivation area of ​​the wafer is corroded by a micro-corrosive liquid, the monocrystalline silicon and polycrystalline silicon in the terminal passivation area are easily corroded, resulting in poor reliability of the double-sided silver fast recovery diode. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a double-sided silver fast recovery diode, which can enable a polyimide layer to be coated on the surface of a terminal passivation region and a first anti-micro-corrosion metal layer, thereby improving the adhesion and reliability of the polyimide layer; at the same time, it will not damage the interior of the terminal passivation region, thereby improving the product yield of the double-sided silver fast recovery diode.

[0005] The embodiment of the present invention is achieved as follows:

[0006] One aspect of the present invention provides a method for preparing a double-sided silver fast recovery diode, comprising:

[0007] A first anti-micro-corrosion metal layer is coated on the front surface of the wafer, wherein the main junction diffusion and terminal passivation have been completed on the front surface of the wafer; a second anti-micro-corrosion metal layer is coated on the surface of the first anti-micro-corrosion metal layer, so that the second anti-micro-corrosion metal layer completely covers the front surface of the wafer; a metal evaporation process is used on the surface of the second anti-micro-corrosion metal layer to deposit titanium / nickel / silver metal layers in sequence to form a front metal; an area of ​​the front metal corresponding to the terminal passivation area of ​​the wafer is corroded until the second anti-micro-corrosion metal layer is exposed, so that the front metal is positively connected to the wafer in the stacking direction. The projection area is smaller than the orthographic projection area of ​​the first anti-micro-corrosion metal layer; the area of ​​the second anti-micro-corrosion metal layer corresponding to the terminal passivation area of ​​the wafer is corroded until the terminal passivation area is exposed, so that the orthographic projection area of ​​the second anti-micro-corrosion metal layer is equal to the orthographic projection area of ​​the front metal; a polyimide layer is covered on the surface of the terminal passivation area, so that the polyimide layer covers the first anti-micro-corrosion metal layer and protrudes from the second anti-micro-corrosion metal layer; a metal evaporation process is used on the back side of the wafer to deposit titanium / nickel / silver metal layers in sequence to form a back side metal.

[0008] Optionally, a first anti-micro-corrosion metal layer is coated on the front surface of the wafer, including: the first anti-micro-corrosion metal layer is a metal aluminum layer.

[0009] Optionally, a second anti-micro-corrosion metal layer is covered on the surface of the first anti-micro-corrosion metal layer, including: the second anti-micro-corrosion metal layer is a metal aluminum layer.

[0010] Optionally, a first anti-micro-corrosion metal layer is coated on the front surface of the wafer, including: a thickness of the first anti-micro-corrosion metal layer is less than or equal to 10 um.

[0011] Optionally, a second anti-micro-corrosion metal layer is covered on the surface of the first anti-micro-corrosion metal layer, comprising: a thickness of the second anti-micro-corrosion metal layer is less than or equal to 2 um.

[0012] Optionally, before a metal evaporation process is used on the back side of the wafer to sequentially deposit titanium / nickel / silver metal layers to form a back side metal, the method further comprises: thinning the back side of the wafer to a thickness of less than 300 um.

[0013] Optionally, a polyimide layer is covered on the surface of the terminal passivation region, including: the thickness of the polyimide layer is 5-10 um.

[0014] Optionally, a metal evaporation process is used on the surface of the second anti-micro-corrosion metal layer to sequentially deposit titanium / nickel / silver metal layers to form a front metal, including: the thickness of the deposited titanium / nickel / silver metal layers is 1000-5000 angstroms, 2000-10000 angstroms, and 5000-15000 angstroms, respectively.

[0015] Optionally, a metal evaporation process is used on the back side of the wafer to sequentially deposit titanium / nickel / silver metal layers to form back side metal, including: the thickness of the deposited titanium / nickel / silver metal layers is 1000-5000 angstroms, 2000-10000 angstroms, and 5000-15000 angstroms, respectively.

[0016] Another aspect of the present invention provides a double-sided silver fast recovery diode, which is manufactured by the above-mentioned method for manufacturing the double-sided silver fast recovery diode.

[0017] The beneficial effects of the present invention include at least one of the following:

[0018] The present application provides a preparation method of a double-sided silver fast recovery diode, comprising: covering a first anti-micro-corrosion metal layer on the front surface of a wafer, wherein the main junction diffusion and terminal passivation have been completed on the front surface of the wafer; covering a second anti-micro-corrosion metal layer on the surface of the first anti-micro-corrosion metal layer, so that the second anti-micro-corrosion metal layer completely covers the front surface of the wafer; by setting the first anti-micro-corrosion metal layer and the second anti-micro-corrosion metal layer, it is possible to prevent the micro-corrosion liquid from directly contacting the terminal passivation area when the front metal is corroded, thereby protecting the single crystal silicon and polycrystalline silicon in the terminal passivation area, and maintaining the electrical parameter stability and reliability of the double-sided silver fast recovery diode; using a metal evaporation process on the surface of the second anti-micro-corrosion metal layer to sequentially deposit titanium / nickel / silver metal layers to form a front metal; and treating the front metal corresponding to the terminal passivation area of ​​the wafer. The first embodiment of the present invention is to etch the area of ​​the wafer in the second anti-micro-corrosion metal layer until the second anti-micro-corrosion metal layer is exposed, so that the positive projection area of ​​the front metal along the stacking direction is smaller than the positive projection area of ​​the first anti-micro-corrosion metal layer; the second anti-micro-corrosion metal layer is etched in the area corresponding to the terminal passivation area of ​​the wafer until the terminal passivation area is exposed, so that the positive projection area of ​​the second anti-micro-corrosion metal layer is equal to the positive projection area of ​​the front metal; the surface of the terminal passivation area is covered with a polyimide layer, so that the polyimide layer covers the first anti-micro-corrosion metal layer and protrudes from a part of the second anti-micro-corrosion metal layer; through such a setting, the direct adhesion of the polyimide layer to the front metal is avoided, and the adhesion of the polyimide layer and the reliability of the double-sided silver fast recovery diode are improved; the back of the wafer is subjected to a metal evaporation process, and titanium / nickel / silver metal layers are deposited in sequence to form a back metal. The above-mentioned preparation method of the double-sided silver fast recovery diode ensures its current flow capacity without damaging the internal part of the terminal passivation area, thereby improving the product yield and reliability of the double-sided silver fast recovery diode.

[0019] The present application also provides a double-sided silver fast recovery diode, which is prepared by the above-mentioned preparation method of the double-sided silver fast recovery diode. The double-sided silver fast recovery diode improves the reliability of use and the product yield while ensuring its current flow capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 A flow chart for preparing a double-sided silver fast recovery diode provided by an embodiment of the present invention;

[0022] Figure 2 One of the structural schematic diagrams of the double-sided silver fast recovery diode during the preparation process provided by the embodiment of the present invention;

[0023] Figure 3 The second structural schematic diagram of the double-sided silver fast recovery diode during the preparation process provided by the embodiment of the present invention;

[0024] Figure 4 The third structural schematic diagram of the double-sided silver fast recovery diode during the preparation process provided by the embodiment of the present invention;

[0025] Figure 5 The fourth structural schematic diagram of the double-sided silver fast recovery diode during the preparation process provided by the embodiment of the present invention.

[0026] Icon: 100-wafer; 110-main junction region; 120-terminal passivation region; 130-first anti-micro-corrosion metal layer; 140-second anti-micro-corrosion metal layer; 150-front metal; 160-polyimide layer; 170-back metal. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0030] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0031] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0032] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] Please refer to Figure 1 This embodiment provides a method for preparing a double-sided silver fast recovery diode, which specifically includes the following steps:

[0034] Step S100, a first anti-micro-corrosion metal layer 130 is formed on the front surface of the wafer 100, wherein the main junction diffusion and terminal passivation have been completed on the front surface of the wafer 100;

[0035] Specifically, Figure 2As shown, the upper surface of the wafer 100 is composed of a main junction region 110 and a terminal passivation region 120 from the center to the outside. The main electrical process will occur in the main junction region 110 to realize the basic functions of the device, such as current conduction, signal processing, etc. The terminal passivation region 120 is located outside the main junction region 110. Its main function is to protect and optimize the edge of the semiconductor device, which can effectively reduce the adverse effects of the surface state and interface state on the device performance. By forming a stable passivation layer, it prevents external environmental factors from interfering with and damaging the internal part of the device, thereby improving the stability, reliability and electrical performance of the double-sided silver fast recovery diode.

[0036] like Figure 2 As shown, the present application first deposits a first anti-micro-corrosion metal layer 130 on the front surface of the wafer 100. The first anti-micro-corrosion metal layer 130 can resist the micro-corrosion liquid that subsequently corrodes the front metal 150. Therefore, when the front metal 150 is subsequently corroded, the first anti-micro-corrosion metal layer 130 can provide a good protective effect on the main junction region 110.

[0037] It should be noted that, first, in a specific embodiment of the present application, the first anti-micro-corrosion metal layer 130 is a metal aluminum layer. Of course, in addition to the metal aluminum layer, the first anti-micro-corrosion metal layer 130 can also be other metal layers that can resist corrosion to micro-corrosion liquid, such as a metal chromium layer, a metal tin layer, etc. The present application does not impose any restrictions on the specific setting form of the first anti-micro-corrosion metal layer 130, as long as it can protect the wafer 100.

[0038] Second, in a specific embodiment of the present application, the thickness of the first anti-micro-corrosion metal layer 130 is less than or equal to 10 um, and such a configuration can save costs and is easier to control during the deposition of the first anti-micro-corrosion metal layer 130. In addition, such a configuration can provide an effective anti-micro-corrosion function while maintaining good thermal conductivity or electrical conductivity of the device.

[0039] Step S200: Figure 2 As shown, a second anti-micro-corrosion metal layer 140 is covered on the surface of the first anti-micro-corrosion metal layer 130, so that the second anti-micro-corrosion metal layer 140 completely covers the front surface of the wafer 100;

[0040] Specifically, Figure 2As shown, after the first anti-micro-corrosion metal layer 130 is covered on the front surface of the wafer 100, a second anti-micro-corrosion metal layer 140 is covered on the surface of the first anti-micro-corrosion metal layer 130, wherein the second anti-micro-corrosion metal layer 140 completely covers the surface of the wafer 100 to ensure that the second anti-micro-corrosion metal layer 140 can shield the terminal passivation area 120 of the wafer 100, thereby ensuring that the subsequent corrosion process of the front metal 150 will not affect the single crystal silicon and polycrystalline silicon in the terminal passivation area 120, so that it has a good protective effect on the terminal passivation area 120.

[0041] It should be noted that, first, in a specific embodiment of the present application, the second anti-micro-corrosion metal layer 140 is a metal aluminum layer. Of course, in addition to the metal aluminum layer, the second anti-micro-corrosion metal layer 140 can also be other metal layers that can resist corrosion to micro-corrosion liquids, such as a metal chromium layer, a metal tin layer, etc. The present application does not impose any restrictions on the specific setting form of the second anti-micro-corrosion metal layer 140, as long as it can protect the terminal passivation area 120 of the wafer 100.

[0042] Second, in a specific embodiment of the present application, the thickness of the second anti-micro-corrosion metal layer 140 is less than or equal to 2 um, and such a configuration can save costs and is easier to control during the deposition of the second anti-micro-corrosion metal layer 140. In addition, such a configuration can provide an effective anti-micro-corrosion function to facilitate the subsequent corrosion removal of the second anti-micro-corrosion metal layer 140 on the surface of the terminal passivation region 120, thereby improving the preparation efficiency of the double-sided silver fast recovery diode.

[0043] Step S300: Figure 2 As shown, a metal evaporation process is used on the surface of the second anti-micro-corrosion metal layer 140 to deposit titanium / nickel / silver metal layers in sequence to form a front metal 150;

[0044] Specifically, if Figure 2 As shown, the present application gradually deposits a uniform metal film on the surface of the second anti-micro-corrosion metal layer 140 through a metal evaporation process. The first deposited is a titanium metal layer. Titanium has good adhesion and diffusion barrier properties, so it can be tightly attached to the surface of the second anti-micro-corrosion metal layer 140, providing a stable and solid foundation for the deposition of subsequent metal layers; at the same time, the titanium metal layer can also effectively prevent other metal atoms from diffusing to the bottom layer, ensuring the stability and purity of the entire metal structure.

[0045] Then, a nickel metal layer is deposited. Nickel further enhances the bonding between metal layers on the titanium layer and helps improve the conductivity and corrosion resistance of the entire metal structure. The presence of the nickel layer allows the subsequently deposited silver metal layer to better exert its excellent conductive properties.

[0046] Finally, a silver metal layer is deposited. Silver has extremely high conductivity and can provide a low-resistance current conduction path for the double-sided silver fast recovery diode during operation, ensuring the efficiency and stability of signal transmission, thereby improving the current conduction capacity of the double-sided silver fast recovery diode.

[0047] It should be noted that, in one possible implementation of the present application, the thickness of the titanium / nickel / silver metal layer deposited in the front metal 150 is 1000-5000 angstroms, 2000-10000 angstroms, and 5000-15000 angstroms, respectively.

[0048] Step S400: Figure 3 As shown, the area of ​​the front metal 150 corresponding to the terminal passivation area 120 of the wafer 100 is corroded until the second anti-micro-corrosion metal layer 140 is exposed, so that the orthographic projection area of ​​the front metal 150 along the stacking direction is smaller than the orthographic projection area of ​​the first anti-micro-corrosion metal layer 130;

[0049] Specifically, when the double-sided silver fast recovery diode is working, an electric field will exist inside it. If the terminal passivation area 120 is properly exposed, the distribution of the electric field at the edge of the chip can be adjusted to make the electric field distribution more uniform, thereby increasing the reverse breakdown voltage of the diode. Therefore, in order to expose the terminal passivation area 120, the front metal 150 and the second anti-micro-corrosion metal layer 140 on the top of the terminal passivation area 120 need to be corroded in turn.

[0050] like Figure 3 As shown, the present application first etches the area of ​​the front metal 150 corresponding to the terminal passivation area 120 of the wafer 100 by photolithography etching until the second anti-micro-corrosion metal layer 140 is exposed. At this time, the second anti-micro-corrosion metal layer 140 can adhere to the surface of the terminal passivation area 120 of the wafer 100, and avoid direct contact between the micro-etching solution of the front metal 150 and the terminal passivation area 120 during photolithography etching.

[0051] During the preparation process of the existing double-sided silver fast recovery diode, when the metal silver layer arranged in the terminal passivation area of ​​the wafer is corroded by a micro-corrosive liquid, the single crystal silicon and polycrystalline silicon in the terminal passivation area are easily corroded, resulting in poor reliability of the double-sided silver fast recovery diode. However, when the metal layer is corroded by the present application, the micro-corrosive liquid can be brought into contact with the second anti-micro-corrosion metal layer 140. Since the second anti-micro-corrosion metal layer 140 is resistant to corrosion by the micro-corrosive liquid, the reliability of the double-sided silver fast recovery diode is improved.

[0052] In this application, when etching the area of ​​the front metal 150 corresponding to the terminal passivation area 120 of the wafer 100, firstly, photoresist is coated on the area of ​​the front metal 150 that does not need to be etched; in the remaining areas that need to be photoetched, the silver metal layer is first etched by silver etching liquid, and then the nickel metal layer and the titanium metal layer are sequentially etched by micro-etching liquid. The micro-etching liquid is mainly composed of a mixed solution of nitric acid, hydrofluoric acid, glacial acetic acid, water, etc. The application does not impose any restrictions on the specific concentration of the micro-etching liquid, and it can be adjusted according to the specific thickness of the front metal 150 in the actual preparation process.

[0053] It should be noted that if Figure 3 As shown, the orthographic projection area of ​​the corroded front metal 150 along the stacking direction is smaller than the orthographic projection area of ​​the first anti-micro-corrosion metal layer 130, so that the area of ​​the uncorroded front metal 150 is smaller than the main junction area 110 of the wafer 100. In this way, the periphery of the first anti-micro-corrosion metal layer 130 can be convex, so that the subsequent polyimide layer 160 can be covered on the periphery of the first anti-micro-corrosion metal layer 130, thereby improving the adhesion of the polyimide layer 160 and the reliability of the double-sided silver fast recovery diode.

[0054] Step S500: Figure 4 As shown, the area of ​​the second anti-micro-corrosion metal layer 140 corresponding to the terminal passivation area 120 of the wafer 100 is corroded until the terminal passivation area 120 is exposed, so that the orthographic projection area of ​​the second anti-micro-corrosion metal layer 140 is equal to the orthographic projection area of ​​the front metal 150;

[0055] Specifically, Figure 4 As shown, after the etching of the area corresponding to the terminal passivation area 120 of the wafer 100 in the front metal 150 is completed, it is necessary to continue to etch the area corresponding to the terminal passivation area 120 of the wafer 100 in the second anti-micro-corrosion metal layer 140 to expose the terminal passivation area 120. Since the uncorroded area is coated with photoresist when the front metal 150 is corroded, the second anti-micro-corrosion metal layer 140 can be directly corroded by the aluminum etching solution. The area of ​​the second anti-micro-corrosion metal layer 140 after corrosion is equal to the area of ​​the front metal 150 after corrosion, so that the periphery of the first anti-micro-corrosion metal layer 130 can be convex, so that the subsequent polyimide layer 160 can be covered on the periphery of the first anti-micro-corrosion metal layer 130.

[0056] Compared with the prior art, the metal silver layer disposed in the terminal passivation region 120 of the wafer 100 is directly corroded by the micro-corrosion liquid, which may cause the micro-corrosion liquid to corrode the single crystal silicon and polycrystalline silicon in the terminal passivation region 120. The present application, by corroding the front metal 150 and the second anti-micro-corrosion metal layer 140 in sequence, can not only corrode the front metal 150 and the second anti-micro-corrosion metal layer 140 at the top of the terminal passivation region 120, but also avoid the micro-corrosion liquid corroding the front metal 150 from directly contacting the second anti-micro-corrosion metal layer 140, thereby protecting the terminal passivation region 120. The aluminum etching liquid used to corrode the second anti-micro-corrosion metal layer 140 is a chemical reagent specifically used for corroding aluminum. Even if it contacts the terminal passivation region 120, it will not react with the single crystal silicon and polycrystalline silicon in the terminal passivation region 120, thereby improving the reliability of the double-sided silver fast recovery diode.

[0057] After the second anti-micro-corrosion metal layer 140 is etched to expose the terminal passivation region 120 , the photoresist coated on the top of the front metal 150 may be removed.

[0058] Step S600: Figure 5 As shown, a polyimide layer 160 is coated on the surface of the terminal passivation region 120, so that the polyimide layer 160 covers the first anti-micro-corrosion metal layer 130 and protrudes from a portion of the second anti-micro-corrosion metal layer 140;

[0059] Specifically, after the terminal passivation region 120 is exposed, in order to provide a certain protection effect on the terminal passivation region 120, a polyimide layer 160 is covered on the surface of the terminal passivation region 120. Polyimide has good insulation properties, which can effectively prevent abnormal conduction of charges between different metal layers or other regions of the chip, reduce the risk of leakage, and ensure the stability of the electrical performance of the chip.

[0060] In the existing preparation method of the double-sided silver fast recovery diode, the side edge of the polyimide layer is usually directly adhered to the surface of the front metal. However, due to the poor adhesion between the polyimide layer and the metallic silver, the polyimide layer is easily warped and falls off, reducing the reliability of the double-sided silver fast recovery diode.

[0061] The preparation method of the double-sided silver fast recovery diode of the present application first corrodes the front metal 150 and the second anti-micro-corrosion metal layer 140. The areas of the front metal 150 and the second anti-micro-corrosion metal layer 140 are both smaller than the first anti-micro-corrosion metal layer 130, that is, the periphery of the first anti-micro-corrosion metal layer 130 protrudes from the front metal 150 and the second anti-micro-corrosion metal layer 140. Through such a setting, when the polyimide layer 160 is covered on the surface of the terminal passivation area 120, its periphery can adhere to the surface of the first anti-micro-corrosion metal layer 130, thereby improving the adsorption of the polyimide layer 160 and improving the reliability of the double-sided silver fast recovery diode.

[0062] It should be noted that, in one possible implementation of the present application, the thickness of the polyimide layer 160 is 5-10 um.

[0063] Step S700: Figure 5 As shown, a metal evaporation process is used on the back side of the wafer 100 to sequentially deposit titanium / nickel / silver metal layers to form a back side metal 170 .

[0064] Specifically, after the front metal 150 of the wafer 100 is prepared, Figure 5 As shown, a back metal 170 may also be prepared on the back side of the wafer 100 to sequentially deposit titanium / nickel / silver metal layers on the back side of the wafer 100 .

[0065] It should be noted that, first, in one possible implementation mode of the present application, the thickness of the titanium / nickel / silver metal layer deposited in the back metal 170 is 1000-5000 angstroms, 2000-10000 angstroms, and 5000-15000 angstroms, respectively.

[0066] Second, before the metal evaporation process is applied to the back side of the wafer 100, the back side of the wafer 100 may be thinned to a thickness of less than 300 um. By thinning the back side of the wafer 100, the heat dissipation efficiency and reliability of the double-sided silver fast recovery diode can be improved.

[0067] The preparation method of the double-sided silver fast recovery diode ensures its current carrying capacity while not damaging the interior of the terminal passivation region 120, thereby improving the product yield and reliability of the double-sided silver fast recovery diode.

[0068] In another aspect of the embodiment of the present application, a double-sided silver fast recovery diode is provided, which is prepared by the preparation method of the double-sided silver fast recovery diode. The double-sided silver fast recovery diode improves the reliability and product yield while ensuring its current flow capacity.

[0069] The above description is only an optional embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0070] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A method for preparing a double-sided silver fast recovery diode, characterized in that: include: A first anti-micro-corrosion metal layer (130) is provided on the front surface of the wafer (100), wherein the main junction diffusion and terminal passivation have been completed on the front surface of the wafer (100); A second anti-micro-corrosion metal layer (140) is provided on the surface of the first anti-micro-corrosion metal layer (130), so that the second anti-micro-corrosion metal layer (140) completely covers the front surface of the wafer (100); Using a metal evaporation process on the surface of the second anti-micro-corrosion metal layer (140), sequentially depositing titanium / nickel / silver metal layers to form a front metal (150); Etching a region of the front metal (150) corresponding to the terminal passivation region (120) of the wafer (100) until the second anti-micro-corrosion metal layer (140) is exposed, so that the orthographic projection area of ​​the front metal (150) along the stacking direction is smaller than the orthographic projection area of ​​the first anti-micro-corrosion metal layer (130); Etching a region of the second anti-micro-corrosion metal layer (140) corresponding to the terminal passivation region (120) of the wafer (100) until the terminal passivation region (120) is exposed, so that the orthographic projection area of ​​the second anti-micro-corrosion metal layer (140) is equal to the orthographic projection area of ​​the front metal (150); A polyimide layer (160) is provided on the surface of the terminal passivation region (120), so that the polyimide layer (160) covers a portion of the first anti-micro-corrosion metal layer (130) protruding from the second anti-micro-corrosion metal layer (140); A metal evaporation process is used on the back side of the wafer (100) to sequentially deposit titanium / nickel / silver metal layers to form a back side metal (170).

2. The method for preparing a double-sided silver fast recovery diode according to claim 1, characterized in that: The first anti-micro-corrosion metal layer (130) is coated on the front surface of the wafer (100), comprising: the first anti-micro-corrosion metal layer (130) is a metal aluminum layer.

3. The method for preparing a double-sided silver fast recovery diode according to claim 1, characterized in that: The second anti-micro-corrosion metal layer (140) is provided on the surface of the first anti-micro-corrosion metal layer (130), comprising: The second anti-micro-corrosion metal layer (140) is a metal aluminum layer.

4. The method for preparing a double-sided silver fast recovery diode according to claim 1, characterized in that: The method of covering the front surface of the wafer (100) with a first anti-micro-corrosion metal layer (130) comprises: The thickness of the first anti-micro-corrosion metal layer (130) is less than or equal to 10 um.

5. The method for preparing a double-sided silver fast recovery diode according to claim 1, characterized in that: The second anti-micro-corrosion metal layer (140) is provided on the surface of the first anti-micro-corrosion metal layer (130), comprising: The thickness of the second anti-micro-corrosion metal layer (140) is less than or equal to 2 um.

6. The method for preparing a double-sided silver fast recovery diode according to claim 1, characterized in that: Before the back side metal (170) is formed by sequentially depositing titanium / nickel / silver metal layers on the back side of the wafer (100) using a metal evaporation process, the method further comprises: The back side of the wafer (100) is thinned to a thickness within 300 um.

7. The method for preparing a double-sided silver fast recovery diode according to claim 1, characterized in that: The polyimide layer (160) is coated on the surface of the terminal passivation region (120), comprising: The thickness of the polyimide layer (160) is 5-10 um.

8. The method for preparing a double-sided silver fast recovery diode according to claim 1, characterized in that: The method of using a metal evaporation process to deposit titanium / nickel / silver metal layers in sequence on the surface of the second anti-micro-corrosion metal layer (140) to form a front metal (150) comprises: The thickness of the deposited titanium / nickel / silver metal layers is 1000-5000 angstroms, 2000-10000 angstroms, and 5000-15000 angstroms, respectively.

9. The method for preparing a double-sided silver fast recovery diode according to claim 1, characterized in that: The back side of the wafer (100) is subjected to a metal evaporation process to deposit titanium / nickel / silver metal layers in sequence to form a back side metal (170), comprising: The thickness of the deposited titanium / nickel / silver metal layers is 1000-5000 angstroms, 2000-10000 angstroms, and 5000-15000 angstroms, respectively.

10. A double-sided silver fast recovery diode, characterized in that: The double-sided silver fast recovery diode is prepared by the preparation method of any one of claims 1 to 9.

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