Joining structure and joining method

Abstract

The present invention provides a joining structure and joining method that can increase the joining strength of the joined objects. [Solution] The joining structure 100 is a joining structure that joins two objects to be joined 10, 20 with their surfaces facing each other. The objects to be joined 10, 20 comprises a base material 11, 21, electrically conductive electrodes 12, 22, and metal material layers 13, 23 that do not function as electrical wiring. The electrodes 12, 22 have electrode surfaces 12a, 22a exposed to the surfaces 10a, 20a. The metal material layers 13, 23 have main surfaces 13a, 23a exposed to the surfaces 10a, 20a. The electrodes 12, 22 of the two objects to be joined 10, 20 are joined with their electrode surfaces 12a, 22a facing each other. The metal material layers 13, 23 of the two objects to be joined 10, 20 are joined with their main surfaces 13a, 23a facing each other.

Description

Technical Field

[0001] The present invention relates to a bonding structure and a bonding method.

Background Art

[0002] As a structure for bonding two substrates having metal electrodes, for example, there is a structure in which two substrates are arranged to face each other and the metal electrodes are bonded to each other (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] In the aforementioned bonding structure, the bonding strength between the two bonded substrates may be insufficient. Therefore, there has been a demand for a structure capable of increasing the bonding strength between two objects to be bonded.

[0005] An aspect of the present invention aims to provide a bonding structure and a bonding method capable of increasing the bonding strength of objects to be bonded.

Means for Solving the Problems

[0006] A bonding structure according to Aspect 1 of the present invention is a bonding structure for bonding two objects to be bonded with their surfaces facing each other, wherein each of the objects to be bonded includes a base material, an energizable electrode, and a metal material layer that does not function as an electrical wiring, the electrode has an electrode surface exposed on the surface, the metal material layer has a main surface exposed on the surface, the electrodes of the two objects to be bonded are bonded with their electrode surfaces facing each other, and the metal material layers of the two objects to be bonded are bonded with their main surfaces facing each other.

[0007] In the bonding structure according to aspect 2 of the present invention, an adhesion layer is formed between the metal material layer and the substrate in the bonding structure according to aspect 1.

[0008] In the bonding structure according to embodiment 3 of the present invention, the shape of the main surface is the same as the shape of the electrode surface in the bonding structure according to embodiment 1 or 2.

[0009] The joining structure according to aspect 4 of the present invention is a joining structure according to any one of aspects 1 to 3, wherein the cross-sectional area of ​​the metal material layer in a cross section perpendicular to the surface is 80% to 120% of the total cross-sectional area of ​​the electrode and the connecting portion extending in the depth direction from the electrode.

[0010] A bonding structure according to aspect 5 of the present invention is a bonding structure according to any one of aspects 1 to 4, wherein the metal material layer comprises a main portion having the main surface and an anchor layer connected to the main portion, and the anchor layer is formed deeper in the substrate than the main portion.

[0011] A bonding structure according to aspect 6 of the present invention is a bonding structure according to any one of aspects 1 to 5, wherein a first low-melting-point metal layer having a lower melting point than the constituent material of the electrodes is formed between the electrodes of the two objects to be bonded, and a second low-melting-point metal layer that bonds the metal material layers together is formed between the metal material layers of the two objects to be bonded.

[0012] The joining structure according to aspect 7 of the present invention is a joining structure according to any one of aspects 1 to 6, wherein the main surface occupies 30% or more of the surface area.

[0013] The bonding structure according to aspect 8 of the present invention is a bonding structure according to any one of aspects 1 to 7, wherein the metal material constituting the metal material layer is the same as the metal material constituting the electrode.

[0014] A joining method according to aspect 9 of the present invention is a joining method for joining two objects to be joined with their surfaces facing each other, comprising: a base material, an electrically conductive electrode, and a metal material layer that does not function as electrical wiring, wherein the electrode has an electrode surface exposed to the surface, and the metal material layer has a main surface exposed to the surface, and the two objects to be joined have their surfaces facing each other; the electrode of the two objects to be joined with their electrode surfaces facing each other, and the metal material layer of the two objects to be joined with their main surfaces facing each other. [Effects of the Invention]

[0015] One aspect of the present invention provides a joining structure and a joining method that can increase the joining strength of the objects to be joined. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic cross-sectional view of a composite substrate having a bonding structure according to the first embodiment. [Figure 2] This is a schematic exploded view of a composite substrate having a bonding structure according to the first embodiment. [Figure 3] This is a schematic cross-sectional view of a composite substrate having a bonding structure according to the second embodiment. [Figure 4] This is a schematic cross-sectional view of a composite substrate having a bonding structure according to the third embodiment. [Figure 5] This is a schematic cross-sectional view of a composite substrate having a bonding structure according to the fourth embodiment. [Figure 6] This is a schematic cross-sectional view of a composite substrate having a bonding structure according to the fifth embodiment. [Modes for carrying out the invention]

[0017] The joining structure and joining method according to the embodiment will be described below with reference to the drawings.

[0018] [Joining structure] (First embodiment) FIG. 1 is a schematic cross-sectional view of a composite substrate 30 having a bonding structure 100 according to the first embodiment. FIG. 2 is a schematic exploded view of the composite substrate 30. In FIG. 1, the X direction and the Y direction are directions parallel to the surface 10a of the first substrate 10. The Y direction is orthogonal to the X direction. The Z direction is orthogonal to the X direction and the Y direction. Plan view refers to viewing from the Z direction. In the present embodiment, the +Z direction is the upward direction. The -Z direction is the direction opposite to the +Z direction. The -Z direction is the downward direction. The XZ plane is a plane including the X direction and the Z direction.

[0019] As shown in FIG. 1 and FIG. 2, the composite substrate 30 includes a first substrate 10 and a second substrate 20. The first substrate 10 and the second substrate 20 are bonded with their surfaces facing each other.

[0020] The first substrate 10 includes a first base material 11, one or more first electrodes 12, one or more first metal material layers 13, a first connection portion 14 extending from the first electrode 12, and a first wiring layer 15 formed in a deep portion of the first base material 11. The surface 10a is the surface of the first substrate 10. In FIG. 1 and FIG. 2, the surface 10a is the upper surface of the first substrate 10.

[0021] The shape of the first substrate 10 in plan view may be, for example, a rectangular shape. The surface 10a of the first substrate 10 faces the surface 20a of the second substrate 20. The first substrate 10 is an example of the "object to be bonded". The first substrate 10 is, for example, a semiconductor substrate. The first substrate 10 may be, for example, a silicon wafer. The first substrate 10 may be a chip cut out from a silicon wafer.

[0022] The first base material 11 is formed of an insulating material such as silicon. The first base material 11 has a plate shape. The surface 11a of the first base material 11 is formed to be flat. The layered region including the surface 11a of the first base material 11 (surface layer region 16) is formed of an oxide (for example, SiO₂) obtained by oxidizing the first base material 11. The first base material 11 is an example of the "base material".

[0023] The electrode surface 12a of the first electrode 12 is exposed to the surface 10a of the first substrate 10. The portion of the first electrode 12 including the electrode surface 12a may protrude upward from the surface 11a of the first substrate 11. If the portion of the first electrode 12 including the electrode surface 12a protrudes from the surface 11a, the bonding strength between the first electrode 12 and the second electrode 22 can be increased. The electrode surface 12a of the first electrode 12 may be formed flush with the surface 11a of the first substrate 11.

[0024] The first electrode 12 is formed of a metallic material such as Cu or a Cu alloy. The first electrode 12 is electrically conductive. The shape of the first electrode 12 in plan view is not particularly limited. The shape of the first electrode 12 in plan view may be, for example, rectangular or circular. The number of first electrodes 12 may be one or multiple (any number of two or more). The first electrode 12 is an example of an "electrode".

[0025] The main surface 13a of the first metal material layer 13 is exposed to the surface 10a of the first substrate 10. The first metal material layer 13 is a layer of a certain thickness formed on the surface 10a of the first substrate 10. The portion of the first metal material layer 13 including the main surface 13a may protrude upward from the surface 11a of the first substrate 11. If the portion of the first metal material layer 13 including the main surface 13a protrudes from the surface 11a, the bonding strength between the first metal material layer 13 and the second metal material layer 23 can be increased. The main surface 13a of the first metal material layer 13 may be formed flush with the surface 11a of the first substrate 11.

[0026] The first metal material layer 13 is formed of a metal material such as Cu or a Cu alloy. It is desirable that the metal material constituting the first metal material layer 13 is the same as the metal material constituting the first electrode 12. If the materials of the first electrode 12 and the first metal material layer 13 are the same, the process of forming the first electrode 12 and the first metal material layer 13 in the manufacturing of the first substrate 10 becomes easier.

[0027] The first metal material layer 13 is formed, for example, in a linear shape extending in the X direction. The shape of the first metal material layer 13 in plan view is not particularly limited. The shape of the first metal material layer 13 in plan view may be, for example, rectangular or circular. The number of first metal material layers 13 may be one or multiple (any number of two or more).

[0028] It is desirable that the main surface 13a of the first metal material layer 13 occupies an area of ​​30% or more of the surface 10a of the first substrate 10. This increases the bonding strength of the first metal material layer 13 to the second substrate 20.

[0029] The first metal material layer 13 does not function as an electrical wiring. The first metal material layer 13 does not need to be electrically conductive. The first metal material layer 13 does not need to be electrically connected to the first electrode 12, the first connection part 14, and the first wiring layer 15. The first metal material layer 13 may be formed in isolation from other wiring, for example. The first metal material layer 13 is an example of a "metal material layer".

[0030] The first connecting portion 14 extends from the first electrode 12 in the depth direction (-Z side) of the first substrate 11. The first connecting portion 14 is formed integrally with the first electrode 12. The external dimensions W14 of the first connecting portion 14 are, for example, equal to the external dimensions W12 of the first electrode 12 (see Figure 2). The first connecting portion 14 is an example of a "connecting portion". The external dimensions are, for example, dimensions in the X direction.

[0031] The first wiring layer 15 is formed deep within the first substrate 11, parallel to the surface 10a of the first substrate 10. The first wiring layer 15 is electrically connected to the lower end (-Z end) of the first connection portion 14. The first electrode 12, the first connection portion 14, and the first wiring layer 15 function as electrical wiring. The first connection portion 14 and the first wiring layer 15 are formed of a metallic material such as Cu or a Cu alloy.

[0032] The second substrate 20 comprises a second base material 21, one or more second electrodes 22, one or more second metal material layers 23, a second connection portion 24 extending from the second electrodes 22, and a second wiring layer 25 formed in the depth of the second base material 21. 20a is the surface of the second substrate 20. In Figures 1 and 2, surface 20a is the bottom surface of the second substrate 20.

[0033] The shape of the second substrate 20 in plan view may be, for example, rectangular. The surface 20a of the second substrate 20 faces the surface 10a of the first substrate 10. The second substrate 20 is an example of the "work to be bonded". The second substrate 20 is, for example, a semiconductor substrate. The second substrate 20 may be, for example, a silicon wafer. The second substrate 20 may also be a chip cut from a silicon wafer.

[0034] The area of ​​surface 20a of the second substrate 20 may be equal to the area of ​​surface 10a of the first substrate 10. The area of ​​surface 20a of the second substrate 20 may be smaller than the area of ​​surface 10a of the first substrate 10. The area of ​​surface 20a of the second substrate 20 may be larger than the area of ​​surface 10a of the first substrate 10.

[0035] The second substrate 21 is formed of an insulating material such as silicon. The second substrate 21 is in the form of a plate. The surface 21a of the second substrate 21 is formed flat. The layered region (surface region 26) including the surface 21a of the second substrate 21 is formed of an oxide (e.g., SiO2) from which the second substrate 21 has been oxidized. The second substrate 21 is an example of a "substrate". The material of the second substrate 21 may be the same as the material of the first substrate 11, or it may be different from the material of the first substrate 11.

[0036] The electrode surface 22a of the second electrode 22 is exposed to the surface 20a of the second substrate 20. The portion of the second electrode 22 including the electrode surface 22a may protrude downward from the surface 21a of the second substrate 21. If the portion of the second electrode 22 including the electrode surface 22a protrudes from the surface 21a, the bonding strength between the first electrode 12 and the second electrode 22 can be increased. The electrode surface 22a of the second electrode 22 may be formed flush with the surface 21a of the second substrate 21.

[0037] The second electrode 22 is formed of a metallic material such as Cu or a Cu alloy. The second electrode 22 is electrically conductive. The shape of the second electrode 22 in plan view is not particularly limited. The shape of the second electrode 22 in plan view may be, for example, rectangular or circular. It is desirable that the shape of the second electrode 22 is the same as the shape of the first electrode 12. At least a part of the second electrode 22 is formed in a position that overlaps with the first electrode 12 in plan view. The number of second electrodes 22 may be one or multiple (any number of two or more). The second electrode 22 is an example of an "electrode".

[0038] The main surface 23a of the second metal material layer 23 is exposed to the surface 20a of the second substrate 20. The second metal material layer 23 is a layer of a certain thickness formed on the surface 20a of the second substrate 20. The portion of the second metal material layer 23 including the main surface 23a may protrude downward from the surface 21a of the second substrate 21. If the portion of the second metal material layer 23 including the main surface 23a protrudes from the surface 21a, the bonding strength between the first metal material layer 13 and the second metal material layer 23 can be increased. The main surface 23a of the second metal material layer 23 may be formed flush with the surface 21a of the second substrate 21.

[0039] The second metal material layer 23 is formed of a metallic material such as Cu or a Cu alloy. It is desirable that the metallic material constituting the second metal material layer 23 is the same as the metallic material constituting the second electrode 22. If the materials of the second electrode 22 and the second metal material layer 23 are the same, the process of forming the second electrode 22 and the second metal material layer 23 in the manufacturing of the second substrate 20 becomes easier.

[0040] The second metal material layer 23 is formed, for example, in a linear shape extending in the X direction. The shape of the second metal material layer 23 in plan view is not particularly limited. The shape of the second metal material layer 23 in plan view may be, for example, rectangular or circular. At least a portion of the second metal material layer 23 is formed in a position that overlaps with the first metal material layer 13 in plan view. The number of second metal material layers 23 may be one or multiple (any number of two or more).

[0041] It is desirable that the main surface 23a of the second metal material layer 23 occupies an area of ​​30% or more of the surface 20a of the second substrate 20. This increases the bonding strength of the second metal material layer 23 to the first substrate 10.

[0042] The second metal material layer 23 does not function as an electrical wiring. The second metal material layer 23 does not need to be electrically conductive. The second metal material layer 23 does not need to be electrically connected to the second electrode 22, the second connection part 24, and the second wiring layer 25. The second metal material layer 23 may be formed in isolation from other wiring, for example. The second metal material layer 23 is an example of a "metal material layer".

[0043] The second connecting portion 24 extends from the second electrode 22 in the depth direction (+Z side) of the second substrate 21. The second connecting portion 24 is formed integrally with the second electrode 22. The external dimensions W24 of the second connecting portion 24 are, for example, equal to the external dimensions W22 of the second electrode 22 (see Figure 2). The second connecting portion 24 is an example of a "connecting portion".

[0044] The second wiring layer 25 is formed deep within the second substrate 21, parallel to the surface 20a of the second substrate 20. The second wiring layer 25 is electrically connected to the upper end (+Z end) of the second connection portion 24. The second electrode 22, the second connection portion 24, and the second wiring layer 25 function as electrical wiring. The second connection portion 24 and the second wiring layer 25 are formed of a metallic material such as Cu or a Cu alloy.

[0045] As shown in Figure 1, electrodes 12 and 22 are joined with their electrode surfaces 12a and 22a facing each other. More specifically, at least a portion of the electrode surface 12a of the first electrode 12 overlaps with the electrode surface 22a of the second electrode 22. At least a portion of electrode surface 12a is joined to electrode surface 22a. At least a portion of the electrode surface 22a of the second electrode 22 overlaps with the electrode surface 12a of the first electrode 12. At least a portion of electrode surface 22a is joined to electrode surface 12a. While only a portion of electrode surface 12a and electrode surface 22a may be joined, it is desirable that the entire areas be joined.

[0046] As a method for joining the first electrode 12 and the second electrode 22, fusion welding (arc welding, laser welding, etc.), pressure welding, brazing, etc. may be used. It is desirable that the first electrode 12 and the second electrode 22 are electrically connected.

[0047] The metal material layers 13 and 23 are joined with their main surfaces 13a and 23a facing each other. More specifically, at least a portion of the main surface 13a of the first metal material layer 13 overlaps with the main surface 23a of the second metal material layer 23. At least a portion of the main surface 13a is joined to the main surface 23a. At least a portion of the main surface 23a of the second metal material layer 23 overlaps with the main surface 13a of the first metal material layer 13. At least a portion of the main surface 23a is joined to the main surface 13a. While only a portion of the main surfaces 13a and 23a may be joined, it is desirable that the entire areas be joined.

[0048] The first metal material layer 13 and the second metal material layer 23 may be joined by fusion welding (arc welding, laser welding, etc.), pressure welding, brazing, etc. The first metal material layer 13 and the second metal material layer 23 may also be electrically connected.

[0049] [Joining method] An example of a joining method according to this embodiment will be described. In the joining method according to this embodiment, the first substrate 10 and the second substrate 20 are joined with their surfaces facing each other as follows.

[0050] (Step 1: Place the two objects to be joined facing each other) As shown in Figure 2, the first substrate 10 and the second substrate 20 are placed facing each other. The first substrate 10 and the second substrate 20 are positioned so that their surfaces 10a and 20a face each other.

[0051] (Second and third steps: bonding of electrodes and bonding of metal material layers) As shown in Figure 1, electrodes 12 and 22 are joined with their electrode surfaces 12a and 22a facing each other. Metal material layers 13 and 23 are joined with their main surfaces 13a and 23a facing each other. The order in which electrodes 12 and 22 are joined and the order in which metal material layers 13 and 23 are joined does not matter. As for the joining method, fusion welding (arc welding, laser welding, etc.), pressure welding, brazing, etc. may be used. A composite substrate 30 is obtained through the above process.

[0052] [Effects of the joining structure and joining method according to the embodiment] In the bonding structure 100 according to this embodiment, the first substrate 10 and the second substrate 20 are provided with metal material layers 13 and 23 that do not function as electrical wiring. The metal material layers 13 and 23 are bonded together with their main surfaces 13a and 23a facing each other. In the bonding structure 100, the bonding strength between the first substrate 10 and the second substrate 20 can be increased compared to a structure without metal material layers.

[0053] In the bonding structure 100, the heat capacity of the composite substrate 30 can be increased by the metal material layers 13 and 23, thereby suppressing the temperature rise at the electrodes 12 and 22, etc.

[0054] In the joining method according to this embodiment, the metal material layers 13 and 23 are joined with their main surfaces 13a and 23a facing each other. Therefore, the bonding strength between the first substrate 10 and the second substrate 20 can be increased.

[0055] [Joining structure] (Second embodiment) Figure 3 is a schematic cross-sectional view of a composite substrate 130 having a bonding structure 200 according to the second embodiment. Components common to other embodiments are denoted by the same reference numerals and their descriptions are omitted.

[0056] As shown in Figure 3, the composite substrate 130 comprises a first substrate 110 and a second substrate 120. The first substrate 110 differs from the first substrate 10 (see Figure 1) in that a first adhesion layer 17 is formed between the first metal material layer 13 and the first substrate 11. The second substrate 120 differs from the second substrate 20 (see Figure 1) in that a second adhesion layer 27 is formed between the second metal material layer 23 and the second substrate 21. The first adhesion layer 17 and the second adhesion layer 27 are examples of "adhesion layers".

[0057] The materials constituting the adhesion layers 17 and 27 include, for example, one or more of Ti, W, and Ta. Examples of materials constituting the adhesion layers 17 and 27 include TiN and TiW. The adhesion layers 17 and 27 can be formed by methods such as CVD (Chemical Vapor Deposition) and sputtering.

[0058] In the bonding structure 200 according to this embodiment, since the first substrate 110 is provided with an adhesion layer 17, the bonding strength between the first metal material layer 13 and the first substrate 11 can be increased. As a result, the first metal material layer 13 becomes less likely to peel off from the first substrate 11. Since the second substrate 120 is provided with an adhesion layer 27, the bonding strength between the second metal material layer 23 and the second substrate 21 can be increased. As a result, the second metal material layer 23 becomes less likely to peel off from the second substrate 21. Thus, the bonding strength between the first substrate 110 and the second substrate 120 can be increased.

[0059] [Joining structure] (Third embodiment) Figure 4 is a schematic cross-sectional view of a composite substrate 230 having a bonding structure 300 according to the third embodiment. Figure 4 shows a cross-section along the XZ plane (a cross-section perpendicular to the surface 10a). Components common to other embodiments are denoted by the same reference numerals and their description is omitted.

[0060] As shown in Figure 4, the composite substrate 230 comprises a first substrate 210 and a second substrate 220. The first substrate 210 differs from the first substrate 10 (see Figure 1) in that it comprises a first metal material layer 213 instead of the first metal material layer 13. 213a is the main surface of the first metal material layer 213. The second substrate 220 differs from the second substrate 20 (see Figure 1) in that it comprises a second metal material layer 223 instead of the second metal material layer 23. 223a is the main surface of the second metal material layer 223.

[0061] It is desirable that the shape of the main surface 213a of the first metal material layer 213 in a plan view be approximately the same as the shape of the electrode surface 12a in a plan view. For example, if the shape of the electrode surface 12a in a plan view is rectangular (e.g., square), it is desirable that the shape of the main surface 213a in a plan view be the same rectangular (e.g., square) shape as the electrode surface 12a. When the shape of the main surface 213a of the first metal material layer 213 is the same as the shape of the electrode surface 12a, the shape, surface condition, etc., of the main surface 213a and the electrode surface 12a can be equalized when the surface of the first substrate 210 is polished. As a result, the bonding state of the electrodes 12, 22 and the metal material layers 213, 223 is good. It is desirable that the area of ​​the main surface 213a is the same as the area of ​​the electrode surface 12a.

[0062] It is desirable that the shape of the main surface 223a of the second metal material layer 223 in a plan view be approximately the same as the shape of the electrode surface 22a in a plan view. For example, if the shape of the electrode surface 22a in a plan view is rectangular (e.g., square), it is desirable that the shape of the main surface 223a in a plan view be the same rectangular (e.g., square) shape as the electrode surface 22a. When the shape of the main surface 223a of the second metal material layer 223 is the same as the shape of the electrode surface 22a, the shape, surface condition, etc., of the main surface 223a and the electrode surface 22a can be equalized when the surface of the second substrate 220 is polished. As a result, the bonding state of the electrodes 12, 22 and the metal material layers 213, 223 is good. It is desirable that the area of ​​the main surface 223a is the same as the area of ​​the electrode surface 22a.

[0063] In manufacturing the composite substrate 230, to form the first electrode 12 and the first connection portion 14, recesses are formed on the surface of the first substrate 11 and filled with a metal material. To form the first metal material layer 213, recesses are formed on the surface of the first substrate 11 and filled with a metal material. To form the second electrode 22 and the second connection portion 24, recesses are formed on the surface of the second substrate 21 and filled with a metal material. To form the second metal material layer 223, recesses are formed on the surface of the second substrate 21 and filled with a metal material.

[0064] In Figure 4, the cross-sectional area of ​​the first metal material layer 213 (area of ​​the cross-section along the XZ plane) is preferably 80% to 120% of the total cross-sectional area of ​​the first electrode 12 and the first connection part 14 (area of ​​the cross-section along the XZ plane). The cross-sectional area of ​​the second metal material layer 223 is preferably 80% to 120% of the total cross-sectional area of ​​the second electrode 22 and the second connection part 24.

[0065] If the cross-sectional area of ​​the first metal material layer 213 is 80% to 120% of the total cross-sectional area of ​​the first electrode 12 and the first connection portion 14, the difference in dimensions (e.g., difference in depth) between the recesses for the first electrode 12 and the first connection portion 14 and the recesses for the first metal material layer 213 becomes smaller, making it easier to form these recesses. Therefore, the manufacturing of the first substrate 210 becomes easier.

[0066] If the cross-sectional area of ​​the second metal material layer 223 is 80% to 120% of the total cross-sectional area of ​​the second electrode 22 and the second connection portion 24, then when forming the second electrode 22, the second connection portion 24, and the second metal material layer 223, the difference in dimensions (e.g., difference in depth) between the recesses for the second electrode 22 and the second connection portion 24 and the recesses for the second metal material layer 223 becomes smaller, making it easier to form these recesses. Therefore, the manufacturing of the second substrate 220 becomes easier.

[0067] [Joining structure] (Fourth embodiment) Figure 5 is a schematic cross-sectional view of a composite substrate 330 having a bonding structure 400 according to the fourth embodiment. Components common to other embodiments are denoted by the same reference numerals and their descriptions are omitted.

[0068] As shown in Figure 5, the composite substrate 330 comprises a first substrate 310 and a second substrate 320. The first substrate 310 differs from the first substrate 10 (see Figure 1) in that it comprises a first metal material layer 313 instead of the first metal material layer 13. 313a is the main surface of the first metal material layer 313. The second substrate 320 differs from the second substrate 20 (see Figure 1) in that it comprises a second metal material layer 323 instead of the second metal material layer 23. 323a is the main surface of the second metal material layer 323.

[0069] The first metal material layer 313 has a main portion 313A having a main surface 313a, an anchor layer 313B, and a connecting portion 313C. The main portion 313A has the same configuration as the first metal material layer 13 (see Figure 1). The anchor layer 313B is formed deeper (-Z side) of the first substrate 11 than the main portion 313A. The anchor layer 313B is formed parallel to the surface of the first substrate 310.

[0070] The connecting portion 313C connects the anchor layer 313B and the main portion 313A. This connects the anchor layer 313B to the main portion 313A. The external dimension Wc1 of the connecting portion 313C is smaller than the external dimension Wb1 of the anchor layer 313B. The external dimension is, for example, the dimension in the X direction. The main portion 313A, the anchor layer 313B, and the connecting portion 313C are integrally formed.

[0071] The second metal material layer 323 has a main portion 323A having a main surface 323a, an anchor layer 323B, and a connecting portion 323C. The main portion 323A has the same configuration as the second metal material layer 23 (see Figure 1). The anchor layer 323B is formed deeper (+Z side) of the second substrate 21 than the main portion 323A. The anchor layer 323B is formed parallel to the surface of the second substrate 320.

[0072] The connecting portion 323C connects the anchor layer 323B and the main portion 323A. This connects the anchor layer 323B to the main portion 323A. The external dimensions Wc2 of the connecting portion 323C are smaller than the external dimensions Wb2 of the anchor layer 323B. The main portion 323A, the anchor layer 323B, and the connecting portion 323C are integrally formed.

[0073] In the bonding structure 400 according to this embodiment, the first metal material layer 313 has an anchor layer 313B, making it difficult for the first metal material layer 313 to peel off from the first substrate 11. The second metal material layer 323 has an anchor layer 323B, making it difficult for the second metal material layer 323 to peel off from the second substrate 21. Therefore, the bonding strength between the first substrate 310 and the second substrate 320 can be increased.

[0074] [Joining structure] (Fifth embodiment) Figure 6 is a schematic cross-sectional view of a composite substrate 430 having a bonding structure 500 according to the fifth embodiment. Components common to other embodiments are denoted by the same reference numerals and their descriptions are omitted.

[0075] The composite substrate 430 comprises a first substrate 10, a second substrate 20, one or more first low-melting-point metal layers 18, and one or more second low-melting-point metal layers 28.

[0076] The first low-melting-point metal layer 18 is formed between the electrode surface 12a of the first electrode 12 and the electrode surface 22a of the second electrode 22. The first low-melting-point metal layer 18 is interposed between the electrode surfaces 12a and 22a, joining the first electrode 12 and the second electrode 22. The metal constituting the first low-melting-point metal layer 18 has a lower melting point than the constituent material of electrodes 12 and 22 (for example, Cu).

[0077] The second low-melting-point metal layer 28 is formed between the main surface 13a of the first metal material layer 13 and the main surface 23a of the second metal material layer 23. The second low-melting-point metal layer 28 is interposed between the main surfaces 13a and 23a, joining the first metal material layer 13 and the second metal material layer 23. The metal constituting the second low-melting-point metal layer 28 has a lower melting point than the constituent materials (e.g., Cu) of the metal material layers 13 and 23.

[0078] The metals constituting the first low-melting-point metal layer 18 and the second low-melting-point metal layer 28 include, for example, one or more of Sn, In, Zn, Pb, Ag, and Au.

[0079] To form the low-melting-point metal layers 18 and 28, for example, the following method can be used: A layer made of the metal is formed between the electrode surfaces 12a and 22a, and between the main surfaces 13a and 23a, respectively, and this layer is heated to a temperature above the melting point of the metal and melted. The molten metal is filled between the electrode surfaces 12a and 22a, and between the main surfaces 13a and 23a. Then the metal is cooled and hardened.

[0080] In the bonding structure 500 according to this embodiment, a first low-melting-point metal layer 18 is formed between the electrode surfaces 12a and 22a, and a second low-melting-point metal layer 28 is formed between the main surfaces 13a and 23a. Therefore, the bonding strength between the first electrode 12 and the second electrode 22, and the bonding strength between the first metal material layer 13 and the second metal material layer 23 can be increased.

[0081] Although the present invention has been described above based on the best mode, the present invention is not limited to the best mode described above, and various modifications are possible without departing from the spirit of the invention. The composite substrate 30 shown in Figure 1 comprises one first substrate 10 and one second substrate 20, but the number of second substrates 20 bonded to the first substrate 10 may be one or multiple. The number of first substrates 10 bonded to the second substrate 20 may be one or multiple. [Explanation of symbols]

[0082] 10,110,210,310 1st substrate (object to be bonded) 11 First base material (base material) 12 1st electrode (electrode) 13 First metal material layer (metal material layer) 14. First connection section (connection section) 17. First Close-Contact Layer (Close-Contact Layer) 18. First low-melting-point metal layer 20,120,220,320 2nd substrate (object to be bonded) 21 Second base material (base material) 22 Second electrode (electrode) 23 Second metal material layer (metal material layer) 24. Second connection section (connection section) 27. Second Close Layer (Close Layer) 28. Second low-melting-point metal layer 100,200,300,400,500 joint structure

Claims

1. A joining structure in which two objects to be joined are joined with their surfaces facing each other, The object to be joined comprises a base material, electrically conductive electrodes, and a metal material layer that does not function as electrical wiring. The electrode has an electrode surface exposed to the surface, The metal material layer has a main surface exposed on the surface, The electrodes of the two objects to be joined are joined with their electrode surfaces facing each other. The metal material layers of the two objects to be joined are joined with their main surfaces facing each other. Joint structure.

2. An adhesion layer is formed between the metal material layer and the substrate. The joining structure according to claim 1.

3. The shape of the main surface is the same as the shape of the electrode surface. The joining structure according to claim 1.

4. The cross-sectional area of ​​the metal material layer in a cross section perpendicular to the surface is 80% to 120% of the total cross-sectional area of ​​the electrode and the connecting portion extending in the depth direction from the electrode. The joining structure according to claim 1.

5. The metal material layer comprises a main portion having the main surface and an anchor layer connected to the main portion. The anchor layer is formed deeper in the substrate than the main portion. The joining structure according to claim 1.

6. A first low-melting-point metal layer, having a lower melting point than the constituent material of the electrodes, is formed between the electrodes of the two objects to be joined. Between the two metal material layers of the objects to be joined, there is a second low-melting-point metal layer that joins the metal material layers together. The joining structure according to claim 1.

7. The main surface occupies 30% or more of the surface area. The joining structure according to claim 1.

8. The metal material constituting the metal layer is the same as the metal material constituting the electrode. The joining structure according to claim 1.

9. A joining method for joining two objects to be joined with their surfaces facing each other, The process involves bringing together the surfaces of two objects to be joined, each comprising a base material, an electrically conductive electrode, and a metal material layer that does not function as an electrical wiring, wherein the electrode has an electrode surface exposed to the surface, and the metal material layer has a main surface exposed to the surface; A step of joining the electrodes of the two objects to be joined with their electrode surfaces facing each other, The process includes the step of joining the metal material layers of two objects to be joined with their main surfaces facing each other. Joining method.

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