A bonding wafer and a wafer bonding method

Abstract

The present application discloses a bonding wafer, comprising: a first wafer and a second wafer arranged opposite to each other, the first wafer having a first concave portion and a second concave portion connected to the bottom of the first concave portion, and the width of the second concave portion is greater than the width of the first concave portion, the second wafer having a first convex portion and a second convex portion corresponding to the first concave portion and the second concave portion; a first metal layer located on the opposite surface of the first wafer and the second wafer; a second metal layer located on the opposite surface of the second wafer and the first wafer; the width of the first concave portion whose sidewall is covered with the first metal layer is not greater than the width of the second convex portion away from one end of the second concave portion. The first metal layer and the second metal layer are mutually fused, and the second convex portion is tightly combined with the first concave portion and the second concave portion of the first wafer, so that there is no gap between the first wafer and the second wafer, thereby improving air tightness. The present application also provides a wafer bonding method with the above advantages.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing process technology, and in particular to a bonding wafer and a wafer bonding method. Background Art

[0002] Wafer bonding technology refers to the process of tightly combining two wafers together through chemical and physical effects. This process can form an airtight cavity for the device, thereby improving the reliability of the device.

[0003] At present, when two wafers are bonded, a sealing ring is formed around each device in the wafer, a bonding point is formed at the electrode of the device, and a through-silicon via and a metal interconnect structure located above the through-silicon via are used to form an electrode connection. Metal materials are deposited at the sealing rings and bonding points formed on the surfaces of the two wafers, and then through bonding technology, under certain conditions, the metals at the bonding points of the two wafers are melted together to complete the bonding process. In addition, there is currently a method of making a raised structure on the bonding point of the wafer located above and then bonding. For large-sized wafers, such as 8-inch and 12-inch, the current bonding method does not make the airtightness of the bonded device good. Due to the large size of the wafer, the uniformity of the thickness of the bonding surface cannot be completely consistent. Therefore, during the bonding process, it is impossible to ensure that the entire surface area of ​​the wafer is well bonded, and there may be regional virtual bonding, especially in the edge area. In the bonding process, since the bonding is carried out between two planes, if there is residue on the surface of the wafer or other residues fall on the bonding surface, it will also cause local poor bonding and affect the airtightness of the device after bonding.

[0004] Therefore, how to solve the above technical problems should be the focus of technical personnel in this field. Summary of the invention

[0005] The purpose of the present application is to provide a bonding wafer and a wafer bonding method to improve the airtightness of the bonded wafer.

[0006] In order to solve the above technical problems, the present application provides a bonding wafer, comprising:

[0007] A first wafer and a second wafer are arranged opposite to each other, wherein the first wafer has a first concave portion and a second concave portion connected to the bottom of the first concave portion, and the width of the second concave portion is greater than the width of the first concave portion, and the second wafer has a first convex portion and a second convex portion corresponding to the first concave portion and the second concave portion, and the first convex portion is connected to the root of the second convex portion;

[0008] A first metal layer located on opposite surfaces of the first wafer and the second wafer;

[0009] A second metal layer located on a surface of the second wafer opposite to the first wafer;

[0010] The width of the first concave portion whose sidewall is covered with the first metal layer is not greater than the width of the second convex portion at an end away from the second concave portion.

[0011] Optionally, a width of an end of the second convex portion close to the second concave portion is smaller than a width of an end of the second convex portion away from the second concave portion.

[0012] Optionally, the first metal layer includes:

[0013] The metal bonding layer located on the opposite surface of the first wafer and the second wafer and the metal bonding layer stacked on the surface of the metal bonding layer, the thickness of the first metal layer is not less than three quarters of the depth of the second recess.

[0014] Optionally, the metal bonding layer is a tin metal layer or a gold metal layer.

[0015] Optionally, the number of the first recess and the number of the second recess are both one;

[0016] Correspondingly, the second wafer further includes a third convex portion located between the first convex portion and the second convex portion.

[0017] Optionally, the height of the second convex portion is equal to the sum of the depths of the first concave portion and the second concave portion.

[0018] The present application also provides a wafer bonding method, comprising:

[0019] Etching the first wafer to form a first concave portion, and etching at the bottom of the first concave portion to form a second concave portion, wherein the width of the second concave portion is greater than the width of the first concave portion;

[0020] forming a first metal layer on the surface of the first wafer having the first recess and the second recess;

[0021] Etching the second wafer to form a second convex portion corresponding to the first concave portion and the second concave portion, and etching the second wafer having the second convex portion to form a first convex portion;

[0022] forming a second metal layer on the surface of the second wafer having the first convex portion and the second convex portion, wherein the width of the first concave portion whose sidewall is covered with the first metal layer is not greater than the width of the second convex portion at one end away from the second concave portion;

[0023] The second protrusion is inserted into the first concave portion, and the first wafer and the second wafer are bonded through the first metal layer and the second metal layer to obtain a bonded wafer.

[0024] Optionally, etching the first wafer to form a first recess, and etching at the bottom of the first recess to form a second recess comprises:

[0025] Making photoresist on the surface of the first wafer;

[0026] Determine the position of the first concave portion on the surface of the first wafer by using photolithography technology, and etch the position by using dry etching technology to form the first concave portion;

[0027] The bottom of the first recess is etched by wet etching technology to form a second recess.

[0028] Optionally, forming a first metal layer on the surface of the first wafer having the first recess and the second recess comprises:

[0029] Making a metal bonding layer on the surface of the first wafer where the first recess and the second recess are formed;

[0030] A metal bonding layer is manufactured on the surface of the metal adhesive layer, and the thickness of the first metal layer is not less than three quarters of the depth of the second recess.

[0031] Optionally, etching the second wafer to form a second convex portion corresponding to the first concave portion and the second concave portion, and etching the second wafer having the second convex portion to form a first convex portion comprises:

[0032] forming a photoresist on a surface of the second wafer;

[0033] Determine the position of the second convex portion by photolithography technology, and form the second convex portion by dry etching technology;

[0034] The position of the first protrusion is determined by photolithography technology, and the first protrusion is formed by dry etching technology.

[0035] A bonding wafer provided in the present application includes a first wafer and a second wafer arranged opposite to each other, the first wafer having a first recess and a second recess connected to the bottom of the first recess, and the width of the second recess is greater than the width of the first recess, the second wafer having a first convex portion and a second convex portion corresponding to the first recess and the second recess, the first convex portion being connected to the root of the second convex portion; a first metal layer located on the opposite surfaces of the first wafer and the second wafer; a second metal layer located on the opposite surfaces of the second wafer and the first wafer; the width of the first recess whose side wall is covered with the first metal layer is not greater than the width of the second convex portion away from the end of the second recess.

[0036] It can be seen that in the present application, the first wafer has a first concave portion and a second concave portion that are connected, and the width of the second concave portion is greater than that of the first concave portion, the first wafer has a first convex portion and a second convex portion corresponding to the first concave portion and the second concave portion, and the surfaces of the first wafer and the second wafer relative to each other have a first metal layer and a second metal layer respectively, that is, the inner surfaces of the first concave portion and the second concave portion are distributed with the first metal layer, the surfaces of the first convex portion and the second convex portion are distributed with the second metal layer, and the width of the first concave portion whose sidewall is covered with the first metal layer is not greater than the width of the second convex portion away from the second concave portion. Therefore, during bonding, the second metal layer is disposed at the end of the second convex portion away from the first concave portion. The two endpoints at the second recess are in close contact with the two endpoints of the first metal layer at the opening of the first recess, and the two endpoints of the second metal layer at the second convex portion near the second recess are in close contact with the metal layer in the second recess, and the first metal layer and the second metal layer are mutually melted after bonding, so there is no gap between the first wafer and the second wafer, and the airtightness is improved. Due to the existence of the second recess, even if there are foreign matter on the bonding surfaces of the first wafer and the second wafer, it will not affect the close contact between the first metal layer and the second metal layer at the second convex portion, the first recess, and the second recess, thereby improving the bonding airtightness while ensuring the performance of the devices on the bonded wafers.

[0037] In addition, the present application also provides a wafer bonding method having the above advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying any creative work.

[0039] Figure 1 A schematic diagram of a partial structure of a bonding wafer provided in an embodiment of the present application;

[0040] Figure 2 is a partial schematic diagram of a first wafer covered with a first metal layer;

[0041] Figure 3 is a partial schematic diagram of a second wafer covered with a second metal layer;

[0042] Figure 4 A schematic diagram of a partial structure of another bonding wafer provided in an embodiment of the present application;

[0043] Figure 5 A flowchart of a wafer bonding method provided in an embodiment of the present application;

[0044] Figures 6 to 14 A process flow chart for forming a bonded wafer;

[0045] Fig.15 Schematic diagram of bonding wafer structure;

[0046] Fig.16 A schematic diagram of a local structure of a bonding wafer after bonding provided in an embodiment of the present application;

[0047] Fig.17 A schematic top view of a bonded wafer after bonding provided in an embodiment of the present application. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0049] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0050] As described in the background technology section, existing bonded wafers are prone to virtual bonding. If there is residue on the wafer surface or other debris on the bonding surface, it will also cause local poor bonding, affecting the airtightness of the device after bonding, and thus affecting performance.

[0051] In view of this, the present application provides a bonding wafer, see Figures 1 to 3 as well as Figures 15 to 17 , Figure 1 A schematic diagram of a partial structure of a bonding wafer provided in an embodiment of the present application, Figure 2 is a partial schematic diagram of a first wafer covered with a first metal layer, Figure 3 is a partial schematic diagram of a second wafer covered with a second metal layer, Fig.15 Schematic diagram of the bonding wafer structure. Fig.16 A schematic diagram of a local structure of a bonding wafer after bonding provided in an embodiment of the present application, Fig.17 A top view of a bonding wafer after bonding provided in an embodiment of the present application, the bonding wafer includes:

[0052] A first wafer 1 and a second wafer 2 are arranged opposite to each other, wherein the first wafer 1 has a first concave portion 11 and a second concave portion 12 connected to the bottom of the first concave portion 11, and the width of the second concave portion 12 is greater than the width of the first concave portion 11, and the second wafer 2 has a first convex portion 21 and a second convex portion 22 corresponding to the first concave portion and the second concave portion, and the first convex portion 21 is connected to the root of the second convex portion 22;

[0053] A first metal layer 3 located on opposite surfaces of the first wafer 1 and the second wafer 2;

[0054] A second metal layer 4 located on the surface of the second wafer 2 opposite to the first wafer 1;

[0055] The width of the first concave portion 11 whose sidewall is covered with the first metal layer 3 is not greater than the width of the second convex portion 22 at one end away from the second concave portion 12 , that is, z≤c.

[0056] The second convex portion 22 is located on the raised surface of the first convex portion 21, and the second convex portion 22 is inserted into the first concave portion 11 and the second concave portion 12. Preferably, the concave portion formed by combining the first concave portion 11 and the second concave portion 12 has a cross-sectional shape of a round bottom flask.

[0057] Specifically, the first metal layer 3 includes:

[0058] The metal bonding layer 31 located on the opposite surface of the first wafer 1 and the second wafer 2 and the metal bonding layer 32 stacked on the surface of the metal bonding layer 31 , the thickness of the first metal layer 3 is not less than three quarters of the depth of the second recess 12 .

[0059] The substrate of the first wafer 1 is silicon. In order to form a good bond between the metal bonding layer 32 and the first wafer 1, a metal bonding layer 31 is firstly provided on the opposite surfaces of the first wafer 1 and the second wafer 2, and then a metal bonding layer 32 is provided. The thickness of the metal bonding layer 32 is much greater than the thickness of the metal adhesive layer, because the width of the second recess 12 is greater than the width of the first recess 11, that is, the second recess 12 protrudes outward relative to the first recess 11, and it is difficult for the metal bonding layer 32 to completely fill the side wall of the second recess 12. Therefore, a thicker metal bonding layer 32 is required to be provided so that the entire second recess 12 is filled with metal during bonding to increase the bonding force. The purpose of the thickness of the metal bonding layer 32 being not less than three quarters of the depth of the second recess 12 is that when the second protrusion 22 with the second metal layer 4 on the surface enters the second recess 12 during bonding, the second metal layer 4 and the metal bonding layer 32 in the second recess 12 are perfectly integrated to ensure that the second recess 12 is filled.

[0060] In this application, the metal bonding layer 31 is not specifically limited. As long as it has good adhesion to silicon, it can meet the requirements. For example, it can be a titanium tungsten bonding layer, a titanium nitride bonding layer, or the like. Similarly, the metal bonding layer 32 in this application is not specifically limited either. As long as it is a bonding layer with ductility. For example, the metal bonding layer 32 is a tin metal layer, a gold metal layer, or the like.

[0061] The second metal layer 4 includes: a first metal bonding layer 41 located on the opposite surface of the second wafer 2 and the first wafer 1, and a first metal bonding layer 42 laminated on the surface of the first metal bonding layer 41. The thickness of the first metal bonding layer 42 is also much greater than the thickness of the first metal bonding layer 41. The first metal bonding layer 41 and the first metal bonding layer 42 on the surface of the second wafer 2 are respectively the same as the metal bonding layer 31 and the metal bonding layer 32 on the surface of the first wafer 1, and will not be elaborated here.

[0062] Preferably, the width of the end of the second protrusion 22 covered with the second metal layer 4 away from the second recess 12 is less than the width of the first recess, and greater than the width of the first recess 11 with the first metal layer 3 covered on the side wall. As Figure 2 and Figure 3 , in order to prevent the second wafer 2 from pressing on the first wafer 1 and causing chipping when bonding the second protrusion 22 to the first recess 11 and the second recess 12 due to too much pressure during bonding, the width c of the second protrusion 22 after forming the second metal layer 4 should be less than the width e of the first recess 11 and greater than the opening width z of the first recess 11 after forming the first metal layer 3, that is, z < c < e. Preferably, the width of the end of the second protrusion 22 close to the second recess 12 is less than the width of the end away from the second recess 12, that is, y < x, so that the second protrusion 22 can be more easily inserted into the first recess 11 and the second recess 12 during bonding.

[0063] Preferably, the height of the second protrusion 22 is equal to the sum of the depths of the first recess 11 and the second recess 12.

[0064] It should be noted that in this application, a device on the wafer is used as an example to describe the bonding of wafers, which is applicable to other devices and electrode connections on the wafer. Further, it should be noted that for the electrode connection structure on the wafer, an electrode layer needs to be provided on the surface of the first wafer 1 before setting the first metal layer 3.

[0065] In the present application, the first wafer 1 has a first concave portion 11 and a second concave portion 12 that are connected, and the width of the second concave portion 12 is greater than that of the first concave portion 11, the first wafer 1 has a first convex portion 21 and a second convex portion 22 corresponding to the first concave portion 11 and the second concave portion 12, and the surfaces of the first wafer 1 and the second wafer 2 relative to each other have a first metal layer 3 and a second metal layer 4, respectively, that is, the first metal layer 3 is distributed on the inner surfaces of the first concave portion 11 and the second concave portion 12, and the second metal layer 4 is distributed on the surfaces of the first convex portion 21 and the second convex portion 22, and the width of the first concave portion 11 whose sidewall is covered with the first metal layer 3 is not greater than the width of the second convex portion 22 away from the second concave portion 12, so during bonding, the second metal layer 4 is disposed on the second concave portion 11. The two endpoints (h, h') of the convex portion 22 away from the second concave portion 12 are in close contact with the two endpoints (g, g') of the first metal layer 3 at the opening of the first concave portion 11, and the two endpoints of the second metal layer 4 at the second convex portion 22 close to the second concave portion 12 are in close contact with the metal layer in the second concave portion 12, and the first metal layer 3 and the second metal layer 4 are mutually melted after bonding, so there is no gap between the first wafer 1 and the second wafer 2, and the airtightness is improved. Due to the existence of the first concave portion 11 and the second concave portion 12, even if there are foreign objects on the bonding surface of the first wafer 1 and the second wafer 2, it will not affect the close contact of the first metal layer 3 and the second metal layer 4 at the second convex portion 22, the first concave portion 11, and the second concave portion 12. Please refer to Fig.16 , while improving the bonding airtightness, ensuring the performance of devices on the bonded wafer.

[0066] See also Figure 4 On the basis of the above embodiments, in one embodiment of the present application, when the number of the first recess 11 and the second recess 12 are both one; accordingly, the second wafer 2 also includes a third convex portion 23 located between the first convex portion 21 and the second convex portion 22.

[0067] It can be understood that the number of the first recess 11 and the second recess 12 are both one, the number of the second protrusion 22 is also one, and the third protrusion 23 is provided to enhance the bonding strength between the first wafer 1 and the second wafer 2 during bonding.

[0068] This application also provides a wafer bonding method, please refer to Figure 5 , Figure 5 A flowchart of a wafer bonding method provided in an embodiment of the present application, the method comprising:

[0069] Step S101: etching a first wafer to form a first recess, and etching a second recess at the bottom of the first recess, wherein the width of the second recess is greater than the width of the first recess.

[0070] Specifically, etching the first wafer to form a first concave portion, and etching the bottom of the first concave portion to form a second concave portion includes:

[0071] Step S1011: fabricating photoresist on the surface of the first wafer.

[0072] Step S1012: determining the position of the first recess on the surface of the first wafer by using photolithography technology, and etching the position by using dry etching technology to form the first recess.

[0073] See also Figure 6 , a first concave portion 11 is formed by etching the surface of the first wafer 1. By controlling the etching time and etching rate, a first concave portion 11 with a preset depth can be obtained. There are multiple first concave portions 11, and only one is shown in the figure as an example.

[0074] Step S1013: using a wet etching technique to etch the bottom of the first recess to form a second recess.

[0075] See also Figure 7 After step S1012, it is not necessary to remove the photoresist, and wet etching is directly performed to form the second recess 12. The etching solution is an isotropic nitric-fluoric acid solution (HNO3+HF+H2O), and the etching of the material silicon of the first wafer is isotropic, and the width of the second recess will be larger than the width of the first recess. After the second recess is etched, the photoresist is removed.

[0076] Step S102: forming a first metal layer on the surface of the first wafer having the first recess and the second recess.

[0077] Optionally, forming a first metal layer on the surface of the first wafer having the first recess and the second recess comprises:

[0078] Step S1021: forming a metal bonding layer on the surface of the first wafer where the first recess and the second recess are formed.

[0079] Preferably, the metal bonding layer 31 is formed by sputtering, see Figure 8 The sputtering method has good step coverage capability, and the formed metal bonding layer has strong adhesion to the silicon surface.

[0080] The metal bonding layer is not specifically limited in the present application, as long as it has good adhesion to silicon, the requirements can be met. For example, it can be a titanium tungsten bonding layer, or a titanium nitride bonding layer, etc.

[0081] Step S1022: manufacturing a metal bonding layer on the surface of the metal adhesive layer, and the thickness of the first metal layer is not less than three quarters of the depth of the second recess.

[0082] Preferably, the metal bonding layer 32 is made by evaporation, see Fig. 9 , the thickness of the metal bonding layer is much greater than that of the metal adhesive layer. Because the width of the second recess is greater than that of the first recess, that is, the second recess protrudes outward relative to the first recess, it is difficult for the metal bonding layer to completely fill the sidewall of the second recess. Therefore, a thicker metal bonding layer is required to fill the entire second recess with metal during bonding to increase the bonding force. The purpose of the thickness of the metal bonding layer being not less than three-quarters of the depth of the second recess is that when the second protrusion covered with the second metal layer on the surface enters the second recess during bonding, the second metal layer and the metal bonding layer in the second recess are perfectly integrated to ensure that the second recess is filled.

[0083] The metal bonding layer in the present application is not specifically limited, as long as it is a bonding layer with ductility. For example, the metal bonding layer is a tin metal layer or a gold metal layer.

[0084] Step S103: etching the second wafer to form a second convex portion corresponding to the first concave portion and the second concave portion, and etching the second wafer having the second convex portion to form a first convex portion, wherein the first convex portion is connected to the root of the second convex portion.

[0085] Specifically, etching the second wafer to form a second convex portion corresponding to the first concave portion and the second concave portion, and etching the second wafer having the second convex portion to form a first convex portion includes:

[0086] Step S1031: fabricating photoresist on the surface of the second wafer.

[0087] Step S1032: determine the position of the second convex portion by photolithography technology, and form the second convex portion by dry etching technology.

[0088] See also Fig.10 , a second convex portion 22 is formed on the second wafer 2 by dry etching technology. The number of the second convex portions 22 corresponds to the number of the first concave portions 11 of the first wafer 1, and only one is shown in the figure as an example. Preferably, by controlling the etching selectivity and the etching angle, the width of the second convex portion 22 close to the second concave portion 12 is smaller than the width of the end away from the second concave portion 12, so that the second convex portion 22 can be more easily inserted into the first concave portion 11 and the second concave portion 12 during bonding.

[0089] Step S1033: determining the position of the first protrusion by photolithography technology, and forming the first protrusion by dry etching technology.

[0090] See also Fig.11, a first protrusion 21 is formed by dry etching technology, and then the photoresist is removed.

[0091] Step S104: forming a second metal layer on the surface of the second wafer having the first protrusion and the second protrusion, wherein a width of the first concave portion whose sidewall is covered with the first metal layer is not greater than a width of the second protrusion at an end away from the second concave portion.

[0092] Specifically, forming a second metal layer on the surface of the second wafer having the first convex portion and the second convex portion includes:

[0093] Step S1041: manufacturing a first metal bonding layer on the surface of the second wafer on which the first protrusion and the second protrusion are formed.

[0094] See also Fig.12 , a first metal bonding layer 41 is formed by sputtering.

[0095] Step S1042: forming a first metal bonding layer on the surface of the metal bonding layer.

[0096] See also Fig.13 The first metal bonding layer 42 is formed by evaporation method, and the thickness of the first metal bonding layer 42 is much greater than that of the first metal adhesive layer 41.

[0097] Step S105: inserting the second protrusion into the first concave portion, and bonding the first wafer and the second wafer through the first metal layer and the second metal layer to obtain a bonded wafer.

[0098] On the basis of the above embodiment, in one embodiment of the present application, when the number of the first concave portion and the number of the second concave portion are both one, before etching the second wafer having the second convex portion to form the first convex portion, the method further includes:

[0099] etching the second wafer having the second protrusion to form a third protrusion;

[0100] Correspondingly, etching the second wafer having the second convex portion to form the first convex portion includes:

[0101] The second wafer having the second protrusion and the third protrusion is etched to form a first protrusion.

[0102] For the structures of the first convex portion 21, the second convex portion 22 and the third convex portion 23, please refer to Fig.14 .

[0103] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0104] The above is a detailed introduction to the bonded wafer and wafer bonding method provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A bonded wafer, characterized in that: include: A first wafer and a second wafer are arranged opposite to each other, wherein the first wafer has a first concave portion and a second concave portion connected to the bottom of the first concave portion, and the width of the second concave portion is greater than the width of the first concave portion, and the second wafer has a first convex portion and a second convex portion corresponding to the first concave portion and the second concave portion, and the first convex portion is connected to the root of the second convex portion; A first metal layer located on opposite surfaces of the first wafer and the second wafer; A second metal layer located on a surface of the second wafer opposite to the first wafer; The width of the first concave portion whose sidewall is covered with the first metal layer is not greater than the width of the second convex portion away from one end of the second concave portion; The first metal layer is distributed on the inner surfaces of the first concave portion and the second concave portion, and the second metal layer is distributed on the surfaces of the first convex portion and the second convex portion; the first wafer and the second wafer are bonded via the first metal layer and the second metal layer.

2. The bonded wafer according to claim 1, wherein: The width of the second convex portion at one end close to the second concave portion is smaller than the width of the second convex portion at one end away from the second concave portion.

3. The bonded wafer according to claim 1, wherein: The first metal layer comprises: The metal bonding layer located on the opposite surface of the first wafer and the second wafer and the metal bonding layer stacked on the surface of the metal bonding layer, the thickness of the first metal layer is not less than three quarters of the depth of the second recess.

4. The bonded wafer according to claim 3, characterized in that: The metal bonding layer is a tin metal layer or a gold metal layer.

5. The bonded wafer according to claim 1, wherein: The number of the first recess and the number of the second recess are both one; Correspondingly, the second wafer further includes a third convex portion located between the first convex portion and the second convex portion.

6. The bonded wafer according to any one of claims 1 to 5, characterized in that: The height of the second convex portion is equal to the sum of the depths of the first concave portion and the second concave portion.

7. A wafer bonding method, characterized in that: include: Etching the first wafer to form a first concave portion, and etching at the bottom of the first concave portion to form a second concave portion, wherein the width of the second concave portion is greater than the width of the first concave portion; A first metal layer is formed on the surface of the first wafer having the first concave portion and the second concave portion; the first metal layer is distributed on the inner surfaces of the first concave portion and the second concave portion; Etching the second wafer to form a second convex portion corresponding to the first concave portion and the second concave portion, and etching the second wafer having the second convex portion to form a first convex portion, wherein the first convex portion is connected to a root of the second convex portion; A second metal layer is formed on the surface of the second wafer having the first convex portion and the second convex portion, wherein the width of the first concave portion whose sidewall is covered with the first metal layer is not greater than the width of the second convex portion at one end away from the second concave portion; and the second metal layer is distributed on the surfaces of the first convex portion and the second convex portion; The second protrusion is inserted into the first concave portion, and the first wafer and the second wafer are bonded through the first metal layer and the second metal layer to obtain a bonded wafer.

8. The wafer bonding method according to claim 7, characterized in that: The etching of the first wafer to form a first concave portion, and etching at the bottom of the first concave portion to form a second concave portion comprises: forming a photoresist on the surface of the first wafer; Determine the position of the first concave portion on the surface of the first wafer by using photolithography technology, and etch the position by using dry etching technology to form the first concave portion; The bottom of the first recess is etched by wet etching technology to form a second recess.

9. The wafer bonding method according to claim 7, characterized in that: The forming of a first metal layer on the surface of the first wafer having the first recess and the second recess comprises: Making a metal bonding layer on the surface of the first wafer where the first recess and the second recess are formed; A metal bonding layer is manufactured on the surface of the metal adhesive layer, and the thickness of the first metal layer is not less than three quarters of the depth of the second recess.

10. The wafer bonding method according to claim 7, characterized in that: The etching of the second wafer to form a second convex portion corresponding to the first concave portion and the second concave portion, and etching of the second wafer having the second convex portion to form a first convex portion comprises: forming a photoresist on the surface of the second wafer; Determine the position of the second convex portion by photolithography technology, and form the second convex portion by dry etching technology; The position of the first protrusion is determined by photolithography technology, and the first protrusion is formed by dry etching technology.

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