Package Structure of Wafer, Power Device and Bonding Method of Wafer Package Structure

Abstract

The present application relates to a packaging structure of a wafer, a power device, and a bonding method of a wafer packaging structure. The packaging structure includes a cathode metal sheet, a wafer, a nanomaterial film, and an anode metal sheet stacked in sequence; the nanomaterial film includes at least one transition layer; the material of the transition layer is an elastic material. In the above packaging structure, by providing a transition layer with elastic deformation ability in the nanomaterial film, the warpage deformation stress of the wafer can be absorbed by the transition layer to release the warpage deformation stress, achieving the effect of reducing the degree of warpage deformation, further reducing the device thermal resistance, improving the long-term reliability of the device, and promoting the application of low-temperature bonding technology in the field of whole-wafer packaging.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor devices, and particularly to a packaging structure of a wafer, a power device, and a bonding method for the wafer packaging structure. Background Art

[0002] As a fully controlled power device with the largest single-tube capacity, the Integrated Gate-Commutated Thyristor (IGCT for short) is widely used in fields such as DC power transmission, smart grid, power converters, and power inverters. With the continuous improvement of the power level of IGCT devices, higher requirements are put forward for the packaging thermal resistance of the devices, and it is necessary to manage the heat of the devices more effectively.

[0003] Currently, the entire wafer of the GCT power device is usually packaged by the nano-silver low-temperature bonding technology. The traditional low-temperature bonding technology uses silver film and silver paste to coat the entire wafer for packaging. However, after bonding, the degree of warping and deformation of the wafer is serious, which seriously affects the optimization effect and reliability of the wafer thermal resistance.

[0004] Therefore, how to reduce the degree of warping and deformation of the wafer during the bonding process has become an urgent problem to be solved in the current semiconductor technology field. Summary of the Invention

[0005] Based on this, in view of the above technical problems, it is necessary to provide a packaging structure of a wafer, a power device, and a bonding method for the wafer packaging structure that can reduce the degree of warping and deformation of the wafer.

[0006] In a first aspect, the present application provides a packaging structure of a wafer, the packaging structure including: a cathode metal sheet, a wafer, a nano-material film, and an anode metal sheet stacked in sequence; the nano-material film includes at least one transition layer; the material of the transition layer is an elastic material.

[0007] In one embodiment, the surface of the transition layer close to the wafer is a convex surface.

[0008] In one embodiment, the surface of the transition layer close to the anode metal sheet is a convex surface.

[0009] In one embodiment, the thickness of the transition layer is 50 - 100 microns; the thickness difference between the thickness of the middle protrusion of the convex surface and the thicknesses of the two edges is 20 - 50 microns.

[0010] In one embodiment, the material of the transition layer includes a metal material with electrical conductivity; preferably, the metal material with electrical conductivity includes at least one of the materials of silver foil and the material of silver-plated copper foil surface.

[0011] In one embodiment, the nanomaterial film further includes at least two layers of nanomaterial layers; each transition layer is disposed between every two adjacent nanomaterial layers.

[0012] In one embodiment, the particle sizes of the materials of the nanomaterial layers are inconsistent.

[0013] In one embodiment, the nanomaterial layer includes a central region and an edge region; the particle size of the material in the edge region gradually increases in a direction away from the central region.

[0014] In one embodiment, the particle size of the material in the central region is 0.05 - 0.1 micrometers; the particle size of the material in the edge region is 0.5 - 1 micrometer.

[0015] In one embodiment, the thickness of the nanomaterial layer is 75 - 50 micrometers.

[0016] In one embodiment, the material of the nanomaterial layer includes a second metal material having electrical conductivity; preferably, the second metal material having electrical conductivity includes at least one of a nanosilver material, a nanocopper material, and a nanosilver / copper composite material.

[0017] In a second aspect, the present application further provides a power device, which includes the packaging structure according to any one of the embodiments of the first aspect.

[0018] In a third aspect, the present application further provides a bonding method for a wafer packaging structure, which is applied to the packaging structure according to any one of the embodiments of the first aspect, and the method includes:

[0019] By a preset coating process, the nanomaterial layer and the transition layer are coated on the surface of the wafer close to the anode metal sheet in an alternating laminated manner to form a nanomaterial film;

[0020] The structure composed of the coated wafer and the nanomaterial film is set under a first preset pressure and a first preset temperature for bonding;

[0021] The anode metal sheet is coated on the surface of the nanomaterial film facing away from the wafer;

[0022] The structure composed of the coated wafer, the nanomaterial film, and the anode metal sheet is set under a second preset pressure and a second preset temperature for bonding.

[0023] The above-mentioned wafer packaging structure, power device, and bonding method of the wafer packaging structure. The packaging structure includes a cathode metal sheet, a wafer, a nano-material film, and an anode metal sheet stacked in sequence; the nano-material film includes at least one transition layer; the material of the transition layer is an elastic material. In the above-mentioned packaging structure, by providing a transition layer with elastic deformation ability in the nano-material film, the warpage deformation stress of the wafer can be absorbed by the transition layer to release the warpage deformation stress, achieving the effect of reducing the degree of warpage deformation, further reducing the device thermal resistance, improving the long-term reliability of the device, and promoting the application of low-temperature bonding technology in the field of whole-wafer packaging. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 Schematic diagram of the wafer packaging structure in one embodiment;

[0026] Figure 2 Schematic diagram of the structure of the transition layer in one embodiment;

[0027] Figure 3 Schematic diagram of the structure of the nano-material film in one embodiment;

[0028] Figure 4 Top view of the structure of the nano-material layer in one embodiment;

[0029] Figure 5 Bonding method of the wafer packaging structure in one embodiment;

[0030] Description of the reference numerals:

[0031] Cathode metal sheet 10; Wafer 20; Nano-material film 30;

[0032] Anode metal sheet 40; Transition layer 301; Nano-material layer 302;

[0033] Central region 3021; Edge region 3022. Detailed Description of the Embodiments

[0034] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant accompanying drawings. Preferred embodiments of the present application are shown in the drawings. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0035] It should be understood that when an element or layer is referred to as "connected to" another element or layer, it can be directly connected to the other element or layer, or there may be intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types, and / or parts, these elements, components, regions, layers, doping types, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type, or part from another element, component, region, layer, doping type, or part.

[0036] Spatial relationship terms such as "above" can be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It should be understood that in addition to the orientation shown in the drawings, spatial relationship terms also include different orientations of the device in use and operation. For example, if the device in the drawing is flipped, the feature described as "above" will be oriented as "below". Therefore, the exemplary term "above" can include both the upper and lower orientations. In addition, the device may also include other orientations (such as rotating 90 degrees or other orientations), and the spatial description terms used herein are accordingly interpreted.

[0037] As used herein, the singular forms "a", "an", and "the" may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that when the terms "comprise" and / or "include" are used in this specification, the presence of the described features, integers, steps, operations, elements, and / or components can be determined, but one or more other features, integers, steps, operations, elements, components, and / or groups are not excluded from existence or addition. At the same time, as used herein, the term "and / or" includes any and all combinations of the related listed items.

[0038] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the ordinary meanings understood by those with ordinary skills in the technical field to which this application belongs. The words such as "a", "an", "one", "the" and the like involved in this application do not indicate a limitation in quantity and may represent a singular or plural number. The terms "comprising", "including", "having" and any variations thereof involved in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may further include steps or units not listed, or may further include other steps or units inherent to these processes, methods, products or devices. The "plurality" involved in this application means greater than or equal to two. "And / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, "A and / or B" may represent: A exists alone, A and B exist simultaneously, and B exists alone. The terms "first", "second" and the like involved in this application are only used to distinguish similar objects and do not represent a specific order for the objects.

[0039] First, before specifically introducing the technical solutions of the embodiments of the present disclosure, the technical background or the technical evolution context based on which the embodiments of the present disclosure are described will be introduced first. As the fully controlled power device with the largest single-tube capacity, the Integrated Gate-Commutated Thyristor (IGCT for short) is widely used in fields such as DC power transmission, smart grid, power converters, and power inverters. With the continuous improvement of the power level of IGCT devices, higher requirements are put forward for the thermal resistance of device packaging, and it is necessary to manage the heat of the device more effectively. Currently, the entire wafer of GCT power devices is usually packaged by the nano-silver low-temperature bonding technology, and the traditional low-temperature bonding technology uses a nano material film and silver paste to coat the entire wafer for packaging. However, after bonding, the warpage deformation degree of the wafer is serious, which seriously affects the thermal resistance optimization effect and reliability of the wafer. Therefore, how to reduce the warpage deformation degree of the wafer during the bonding process has become an urgent problem to be solved in the current semiconductor technology field.

[0040] This application provides a packaging structure for a wafer, as Figure 1 shown. The packaging structure includes: a cathode metal sheet 10, a wafer 20, a nano material film 30, and an anode metal sheet 40 stacked in sequence; the nano material film 30 includes at least one transition layer 301; the material of the transition layer 301 is an elastic material.

[0041] The above elastic material has a certain elastic deformation ability and is used to absorb the warpage deformation stress of the wafer 20. The elastic material is a highly elastic metal and its composite material with certain electrical conductivity and thermal conductivity. The elastic modulus of the elastic material can be set according to actual needs.

[0042] The thickness of the above-mentioned transition layer 301 is 50 - 100 microns. The material of the transition layer 301 is a material that can be directly pre-sintered with nano silver, including metal materials with electrical conductivity; preferably, the metal materials with electrical conductivity include at least one of the materials of silver foil and the material of silver-plated copper foil. The selection of the material of the transition layer 301 needs to follow the principle of being able to complete the bonding process. Specifically, the selection of the material of the transition layer 301 and the surface metallization material follows the principle of being bondable with the nano material layer, preferably the same material as the nano material layer or a gold material with excellent performance. The specific material type can be set according to actual needs. Among them, the nano material layer is the material layer to be bonded with the transition layer 301. The shapes of the upper surface and the lower surface of the transition layer 301 can be the same or different.

[0043] The wafer packaging structure provided by the embodiment of the present application can absorb the warpage deformation stress of the wafer through the transition layer with elastic deformation ability provided in the nano material film, release the warpage deformation stress, achieve the effect of reducing the degree of warpage deformation, and further reduce the device thermal resistance and improve the long-term reliability of the device, which can promote the application of the low-temperature bonding technology in the field of whole-wafer packaging.

[0044] In one embodiment, the surface of the above-mentioned transition layer 301 close to the wafer 20 is a convex surface and / or the surface of the above-mentioned transition layer 301 close to the anode metal sheet 40 is a convex surface.

[0045] Among them, the surface of the transition layer 301 close to the wafer 20 is the upper surface of the transition layer 301, and the surface of the transition layer 301 close to the anode metal sheet 40 is the lower surface of the transition layer 301.

[0046] In the embodiment of the present application, the upper surface of the transition layer 301 can be a flat surface or a convex surface; the lower surface of the transition layer 301 can be a flat surface or a convex surface. Then there are four cases. The first is that both the upper surface and the lower surface of the transition layer 301 are flat surfaces; the second is that both the upper surface and the lower surface of the transition layer 301 are convex surfaces, and specifically, reference can be made to Figure 2 the structure of the transition layer 301 shown; the third is that the upper surface of the transition layer 301 is a flat surface and the lower surface is a convex surface; the fourth is that the upper surface of the transition layer 301 is a convex surface and the lower surface is a flat surface. In the packaging structure described in the embodiment of the present application, by setting the surface of the transition layer as a convex surface, since the convex direction of the convex surface is opposite to the direction of the wafer warpage deformation, when the wafer is about to warp and deform, the convex surface can offset the wafer warpage deformation stress, achieving the effect of reducing the degree of warpage deformation.

[0047] In one embodiment, the above-mentioned nanomaterial film 30 further includes at least two layers of nanomaterial layers 302; each transition layer 301 is disposed between every two adjacent nanomaterial layers 302.

[0048] Among them, the thickness of the nanomaterial layer 302 is 75 - 50 microns. The material of the nanomaterial layer 302 includes a second metal material with electrical conductivity; preferably, the second metal material with electrical conductivity includes at least one of nanosilver material, nanocopper material, and nanosilver composite material. For example, the nanomaterial film 30 can be a silver film. The nanomaterial layer 302 is printed on both sides of the transition layer 301.

[0049] In the embodiment of the present application, the nanomaterial film can be composed of at least one transition layer 301 and nanomaterial layer 302. For example, as Figure 3 shown, the nanomaterial film can be a "sandwich structure", sequentially including nanomaterial layer 302 - transition layer 301 - nanomaterial layer 302. Optionally, it can also be a multi-layer structure, sequentially including nanomaterial layer 302 - transition layer 301 - nanomaterial layer 302 - transition layer 301 -... - nanomaterial layer 302. Optionally, it can also sequentially include nanomaterial layer 302 - transition layer 301 - transition layer 301 -... - transition layer 301 - nanomaterial layer 302. The above packaging structure can release the warping deformation stress by increasing the overall thickness of the entire nanomaterial.

[0050] In one embodiment, the particle sizes of the materials of the above-mentioned nanomaterial layer are inconsistent.

[0051] In the embodiment of the present application, the particle size of the material of the nanomaterial layer is set with the goal of reducing the degree of wafer warping deformation, and can be specifically determined according to the degree of wafer warping deformation at each position. Optionally, the particle size of the intermediate material of the nanomaterial layer can be larger or smaller than that of the edge material. Optionally, the particle size of the material of the nanomaterial layer can gradually increase or decrease from the middle to the edge, showing a gradual change process.

[0052] Preferably, the above-mentioned nanomaterial layer 302 includes a central region 3021 and an edge region 3022; the particle size of the material in the edge region 3022 gradually increases in the direction away from the central region 3021. The particle size of the material in the central region is 0.05 - 0.1 microns; the particle size of the material in the edge region is 0.5 - 1 micron. The shapes of the central region 3021 and the edge region 3022 can be circular, square, or polygonal, and the specific shape is set according to actual needs, and is not limited in the embodiment of the present application. For example, as Figure 4Top view of the nanomaterial layer 302 shown, wherein both the central region 3021 and the edge region 3022 are circular. Among them, the central region 3021 is a dense ring, and the edge region 3022 is a loose ring. In the encapsulation structure described in the embodiments of the present application, by optimizing the radial looseness / density of the nanomaterial, the elastic modulus of a specific region is increased, and the warping deformation stress is released. The particle size of the material of the nanomaterial layer can be such that the particle size of the material in the intermediate layer is smaller than that in the edge layer, and the particle size of the material gradually increases from the middle to the edge. The particle size of the material at a specific position,

[0053] Regarding the encapsulation structure of the wafer described in all the above embodiments, the present application also provides an encapsulation structure of a wafer, which includes: a cathode metal sheet 10, a wafer 20, a nanomaterial film 30, and an anode metal sheet 40 stacked in sequence;

[0054] The nanomaterial film 30 includes at least one transition layer. The material of the transition layer 301 is an elastic material, which has a certain elastic deformation ability and is used to absorb the warping deformation stress of the wafer 20. The elastic modulus of the elastic material can be set according to actual needs. The surface of the transition layer 301 close to the wafer 20 is a convex surface, and the surface of the transition layer 301 close to the anode metal sheet 40 is a convex surface. The thickness difference between the thickness of the middle protrusion and the thickness of the two edges of the convex surface is 20 - 50 microns, and the thickness of the transition layer 301 is 50 - 100 microns. The material of the transition layer 301 is a material that can be directly pre-sintered with nano silver, including a metal material with electrical conductivity; preferably, the metal material with electrical conductivity includes at least one of the materials of silver foil and the material of silver-plated copper foil. The shapes of the upper surfaces of the transition layer 301 can be the same or different. The upper surface of the transition layer 301 can be a flat surface or a convex surface; the lower surface of the transition layer 301 can be a flat surface or a convex surface. Then there are four cases. The first is that both the upper surface and the lower surface of the transition layer 301 are flat surfaces; the second is that both the upper surface and the lower surface of the transition layer 301 are convex surfaces; the third is that the upper surface of the transition layer 301 is a flat surface and the lower surface is a convex surface; the fourth is that the upper surface of the transition layer 301 is a convex surface and the lower surface is a flat surface.

[0055] The nano-material film 30 further includes at least two layers of nano-material layers 302. Each transition layer 301 is disposed between every two adjacent nano-material layers 302. The nano-material layer 302 includes a central region 3021 and an edge region 3022. The particle size of the material in the edge region 3022 gradually increases in a direction away from the central region 3021. The particle size of the material in the central region 3021 is 0.05 - 0.1 micrometers, and the particle size of the material in the edge region 3022 is 0.5 - 1 micrometers. The shapes of the central region 3021 and the edge region 3022 can be circular, square, or polygonal. The specific shape is set according to actual requirements and is not limited in the embodiments of the present application. The thickness of the nano-material layer 302 is 75 - 50 micrometers. The material of the nano-material layer 302 includes a second metal material with electrical conductivity; preferably, a second metal material with electrical conductivity. The nano-material film can be a "sandwich structure", sequentially including a nano-material layer 302 - a transition layer 301 - a nano-material layer 302. Optionally, it can also be a multi-layer structure, sequentially including a nano-material layer 302 - a transition layer 301 - a nano-material layer 302 - a transition layer 301 -... - a nano-material layer 302. Optionally, it can also sequentially include a nano-material layer 302 - a transition layer 301 - a transition layer 301 -... - a transition layer 301 - a nano-material layer 302.

[0056] In the packaging structure described in the embodiments of the present application, by providing a transition layer with elastic deformation ability in the nano-material film, the warpage deformation stress of the wafer can be absorbed by the transition layer to release the warpage deformation stress, achieving the effect of reducing the degree of warpage deformation. Furthermore, the thermal resistance of the device can be further reduced, and the long-term reliability of the device can be improved, which can promote the application of the low-temperature bonding technology in the field of whole-wafer packaging. By setting the surface of the transition layer as a convex surface, since the convex direction of the convex surface is opposite to the direction of the wafer warpage deformation, when the wafer is about to warp and deform, the warpage deformation stress of the wafer can be offset by the convex surface, achieving the effect of reducing the degree of warpage deformation. By increasing the overall thickness of the entire nano-material, the warpage deformation stress can be released. By optimizing the radial looseness / density of the nano-material and increasing the elastic modulus of a specific region, the warpage deformation stress can be released.

[0057] Based on the packaging structure of the wafer described in all the above embodiments, the present application further provides a power device, which includes the packaging structure of any one of the above embodiments.

[0058] In the power device described in the embodiments of the present application, by providing a transition layer with elastic deformation ability in the nano-material film in the packaging structure, the warpage deformation stress of the wafer can be absorbed by the transition layer to release the warpage deformation stress, achieving the effect of reducing the degree of warpage deformation. Furthermore, the device thermal resistance can be further reduced, and the long-term reliability of the device can be improved, which can promote the application of the low-temperature bonding technology in the field of whole-wafer packaging. By setting the surface of the transition layer as a convex surface, since the convex direction of the convex surface is opposite to the direction of the wafer warpage deformation, when the wafer is about to warp and deform, the warpage deformation stress of the wafer can be offset by the convex surface, achieving the effect of reducing the degree of warpage deformation. By increasing the overall thickness of the entire nano-material, the warpage deformation stress can be released. By optimizing the radial looseness / density of the nano-material and increasing the elastic modulus of a specific area, the warpage deformation stress can be released.

[0059] Based on the packaging structure of the wafer described in all the above embodiments, the present application further provides a bonding method for the wafer packaging structure. This method is applied to the packaging structure of any of the above embodiments, as Figure 5 shown, and this method includes:

[0060] S101, through a preset coating process, the nano-material layer and the transition layer are alternately laminated and coated on the surface of the wafer close to the anode metal sheet to form a nano-material film, so as to achieve the pre-bonding operation.

[0061] S102, the structure composed of the coated wafer and the nano-material film is set under a first preset pressure and a first preset temperature for bonding.

[0062] S103, the anode metal sheet is coated on the surface of the nano-material film away from the wafer.

[0063] S104, the structure composed of the coated wafer, the nano-material film and the anode metal sheet is set under a second preset pressure and a second preset temperature for bonding.

[0064] Among them, the preset coating process can be to coat the nano-material layer on the surface of the transition layer by using the screen printing process. The first preset pressure and the second preset pressure can be the same or different. The first preset temperature and the second preset temperature can be the same or different. The process parameters can be: 150 - 180 °C / 3 - 5 MPa / 30 - 60 s. The above-mentioned nano-material film after pre-bonding can be stored in vacuum.

[0065] In the embodiments of the present application, the anode metal sheet / wafer can be assembled by a specially designed fixture, and the low-temperature bonding process can be completed by using a specific bonding device.

[0066] Optionally, a nanomaterial film (e.g., silver film) can also be prepared in advance, and then the prepared nanomaterial film can be used to complete the packaging process of the wafer. Specifically, the following steps can be included: First, the nanomaterial is coated on the transition layer by means of heating and pressure bonding to complete the preparation of the silver film. Then, the surface of the anode metal sheet is metallized. The metallization material in this process can be a material that can be wetted by composite silver film materials such as silver or gold. Finally, the anode metal sheet, the silver film, and the wafer are bonded to achieve the packaging process of the wafer.

[0067] In the bonding method of the wafer packaging structure described in the embodiments of the present application, through a preset coating process, the nanomaterial layer and the transition layer are coated on the surface of the wafer close to the anode metal sheet in an alternating laminated manner to form a nanomaterial film to achieve a pre-bonding operation. Then, the structure composed of the coated wafer and the nanomaterial film is set at a first preset pressure and a first preset temperature for bonding. Then, the anode metal sheet is coated on the surface of the nanomaterial film facing away from the wafer. Finally, the structure composed of the coated wafer, the nanomaterial film, and the anode metal sheet is set at a second preset pressure and a second preset temperature for bonding. In the above method, by setting a transition layer with elastic deformation ability in the nanomaterial film in the packaging structure, the warpage deformation stress of the wafer can be absorbed by the transition layer to release the warpage deformation stress, achieving the effect of reducing the degree of warpage deformation. Furthermore, the device thermal resistance can be further reduced, and the long-term reliability of the device can be improved, which can promote the application of the low-temperature bonding technology in the field of whole-wafer packaging. By setting the surface of the transition layer as a convex surface, since the convex direction of the convex surface is opposite to the direction of the wafer warpage deformation, when the wafer is about to generate warpage deformation, the warpage deformation stress of the wafer can be offset by the convex surface, achieving the effect of reducing the degree of warpage deformation. By increasing the overall thickness of the entire nanomaterial, the warpage deformation stress can be released. By optimizing the radial looseness / density of the nanomaterial and increasing the elastic modulus in a specific area, the warpage deformation stress can be released.

[0068] It should be understood that although the steps in the flowcharts involved in the above-described embodiments are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear indication in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-described embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be executed alternately or alternately with at least a part of other steps or steps in other steps.

[0069] In the description of this specification, the descriptions referring to terms such as "some embodiments", "other embodiments", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0070] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0071] The above-described embodiments merely represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A wafer packaging structure, characterized in that: The packaging structure comprises: a cathode metal sheet, a wafer, a nano material film and an anode metal sheet stacked in sequence; the nano material film comprises at least one transition layer; the material of the transition layer is an elastic material; Among them, the surface of the transition layer close to the wafer is convex; the surface of the transition layer close to the anode metal sheet is convex; the thickness of the transition layer is 50-100 microns; the thickness difference between the middle protrusion of the convex surface and the thickness of the two edges is 20-50 microns; the nanomaterial film also includes at least two layers of nanomaterial layers; each of the transition layers is arranged between each two adjacent nanomaterial layers.

2. The packaging structure according to claim 1, characterized in that: The material of the transition layer includes a first metal material with conductive properties; the first metal material with conductive properties includes at least one of a silver foil material and a copper foil surface-plated silver material.

3. The packaging structure according to claim 1, characterized in that: The material particle sizes of the nano material layer are inconsistent.

4. The packaging structure according to claim 3, characterized in that: The nano material layer includes a central area and an edge area; the particle size of the material in the edge area gradually increases in a direction away from the central area.

5. The packaging structure according to claim 4, characterized in that: The particle size of the material in the central area is 0.05-0.1 micrometers; the particle size of the material in the edge area is 0.5-1 micrometers.

6. The packaging structure according to claim 1, characterized in that: The thickness of the nano material layer is 75-50 microns.

7. The packaging structure according to claim 1, characterized in that: The material of the nano material layer includes a second metal material with conductive properties; the second metal material with conductive properties includes at least one of nano silver material, nano copper material, and nano silver / copper composite material.

8. A power device, characterized in that: The power device comprises the packaging structure according to any one of claims 1 to 7.

9. A bonding method for a wafer packaging structure, characterized in that: The method is applied to the packaging structure according to any one of claims 1 to 7, and the method comprises: Through a preset coating process, the nano material layer and the transition layer are coated on the surface of the wafer close to the anode metal sheet in an alternating manner to form a nano material film; Bonding the coated wafer and the structure formed by the nano material film at a first preset pressure and a first preset temperature; Coating the anode metal sheet on the surface of the nanomaterial film facing away from the wafer; The structure consisting of the coated wafer, the nano material film and the anode metal sheet is set at a second preset pressure and a second preset temperature for bonding.

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