Semiconductor device and method for manufacturing semiconductor device

Abstract

A bonding layer (18) is provided in which the same number of first layers (14) and second layers (16) both having conductivity are alternately stacked in sequence on a semiconductor substrate (10). A metal layer (24) is provided on the bonding layer (18). The first layer (14) is composed of a material containing an element constituting the semiconductor substrate (10). The bonding between the second layer (16) and the metal layer (24) is higher than that between the first layer (14). The bonding layer (18) has a total of more than 4 layers of first layers (14) and second layers (16). Among the first layers (14) and second layers (16) constituting the bonding layer (18), if the second layer (16) in contact with the metal layer (24) is removed, the first layer (14) in contact with the semiconductor substrate (10) has the thickest film thickness, and if the first layer (14) in contact with the semiconductor substrate (10) is removed, the second layer (16) in contact with the metal layer (24) has the thickest film thickness.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor device and a method for manufacturing the semiconductor device. Background Art

[0002] A semiconductor device having an adhesive layer interposed between a semiconductor substrate and a metal layer is disclosed (for example, see Patent Document 1). The adhesive layer interposed between the semiconductor substrate and the metal layer can improve the adhesiveness between the semiconductor substrate and the metal layer.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2014-112634

[0004] However, in the above-mentioned semiconductor device, sometimes the adhesion between the semiconductor substrate and the metal layer is insufficient. For example, when the semiconductor substrate is composed of SiC, if the adhesion layer uses commonly used Ti or Ni, the adhesion between the semiconductor substrate and the adhesion layer is insufficient. This is because the adhesion between SiC and Ti or Ni is insufficient.

[0005] In order to solve the problem of insufficient adhesion, it can be considered that the close-contact layer is set to a two-layer structure. In these two layers, the layer (first layer) in contact with the semiconductor substrate is formed by the material with high adhesion between the semiconductor substrate, and the layer (second layer) in contact with the metal layer is formed by the material with high adhesion between the metal layer. However, in this case, since only one interface is formed in the close-contact layer, when the close-contact layer is stressed as the semiconductor device has warped, the stress is concentrated on this one interface. Stress concentration causes film peeling, film floating, etc. at the interface. That is, the close adhesion of the semiconductor substrate and the metal layer is reduced.

[0006] In order to solve the problem that the adhesion reduces, it can be considered that by setting the adhesion layer to the structure repeated by the first layer and the second layer, and forming multiple interfaces in the adhesion layer, stress concentration is prevented. However, in this case, due to the increase in the number of films, the thickness of the adhesion layer thickens, and the resistance in the thickness direction of the adhesion layer increases. If the thickness of the first layer and the second layer is thinned in order to suppress the thickness of the adhesion layer to be thin, then this time the composition of the second layer can be caused to move to the interface near the semiconductor substrate and the first layer due to diffusion, therefore causing the adhesion at the interface to reduce. This problem also occurs at the interface of the metal layer and the second layer. Summary of the invention

[0007] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to obtain a semiconductor device and a method for manufacturing a semiconductor device in which the adhesion between a semiconductor substrate and a metal layer is prevented from being reduced and a thickness of an adhesion layer is suppressed.

[0008] The semiconductor device involved in the disclosure comprises: a semiconductor substrate having a first surface and a second surface facing each other; a bonding layer formed by alternately stacking the same number of first layers and second layers both having conductivity on the first surface; and a metal layer formed on the bonding layer, wherein the first layer is composed of a material containing elements constituting the semiconductor substrate, the second layer has higher bonding properties with the metal layer than the first layer, the bonding layer has a total of more than 4 first layers and second layers, and among the first layers and second layers constituting the bonding layer, if the second layer in contact with the metal layer is removed, the first layer in contact with the semiconductor substrate has the thickest film thickness, and if the first layer in contact with the semiconductor substrate is removed, the second layer in contact with the metal layer has the thickest film thickness.

[0009] In addition, the manufacturing method of the semiconductor device involved in the disclosure comprises the following steps: a first step, forming the same number of first layers and second layers both having conductivity on a semiconductor substrate alternately in sequence; and a second step, forming a metal layer on the second layer formed last in the first step, the first layer being composed of a material containing elements constituting the semiconductor substrate, and the second layer having higher adhesion to the metal layer than the first layer, in the first step, using the ALD method, forming a total of more than 4 layers of first layers and second layers continuously in the same chamber, and among the first and second layers formed in the first step, if the second layer in contact with the metal layer is removed, the first layer in contact with the semiconductor substrate has the thickest film thickness, and if the first layer in contact with the semiconductor substrate is removed, the second layer in contact with the metal layer has the thickest film thickness.

[0010] According to the semiconductor device and the method for manufacturing the semiconductor device disclosed in the present invention, the first layer is composed of a material containing an element constituting the semiconductor substrate. In addition, of the first layer and the second layer, if the second layer in contact with the metal layer is removed, the first layer in contact with the semiconductor substrate has the thickest film thickness, and if the first layer in contact with the semiconductor substrate is removed, the second layer in contact with the metal layer has the thickest film thickness. Therefore, it is possible to obtain a semiconductor device that prevents the decrease in the adhesion between the semiconductor substrate and the metal layer and suppresses the adhesion layer to be thin. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a cross-sectional view showing the semiconductor device according to the first embodiment.

[0012] Figure 2 This is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to the first embodiment.

[0013] Figure 3 It is a cross-sectional view showing a semiconductor device according to the second embodiment.

[0014] Figure 4 Is magnification Figure 3 A diagram obtained from a part of .

[0015] Figure 5 This is a cross-sectional view for explaining a method for manufacturing a semiconductor device according to the second embodiment. DETAILED DESCRIPTION

[0016] Implementation Method 1

[0017] The structure of the semiconductor device according to the first embodiment is described. Figure 1 A semiconductor device 10 is shown. Figure 1 is a cross-sectional view of the semiconductor device 10 .

[0018] The semiconductor device 10 includes a semiconductor substrate 12. The semiconductor substrate 12 has a first surface 14 and a second surface 16 facing each other. The semiconductor substrate 12 is made of SiC, for example.

[0019] A bonding layer 18 is formed on the first surface 14 of the semiconductor substrate 12. The bonding layer 18 is stacked alternately with the same number of first layers 20 and second layers 22 in sequence from the first surface 14 side. The first layer 20 and the second layer 22 are both conductive. The first layer 20 is composed of a material containing an element constituting the semiconductor substrate 12, such as Si. The second layer 22 is composed of Ti, for example. The bonding layer 18 only needs to have a total of 4 or more first layers 20 and second layers 22, preferably 6 or more layers.

[0020] A metal layer 24 is formed on the adhesion layer 18. The metal layer 24 is made of, for example, Au. A material having higher adhesion to the metal layer 24 than the first layer 20 is used for the second layer 22.

[0021] Of the first layer 20 and the second layer 22 constituting the adhesion layer 18, if the second layer 22 in contact with the metal layer 24 is removed, the first layer 20 in contact with the semiconductor substrate 12 has the thickest film thickness. In addition, if the first layer 20 in contact with the semiconductor substrate 12 is removed, the second layer 22 in contact with the metal layer 24 has the thickest film thickness. The film thickness of the first layer 20 in contact with the semiconductor substrate 12 is, for example, 15 nm. The film thickness of the first layer 20 in contact with the metal layer 12 is, for example, 15 nm. In order to prevent the components of the second layer 22 located above the first layer 20 from moving to the vicinity of the interface between the semiconductor substrate 12 and the first layer 20, the film thickness of the first layer 20 in contact with the semiconductor substrate 12 is preferably greater than 10 nm. Similarly, in order to prevent the components of the first layer 20 located below the second layer 22 from moving to the vicinity of the interface between the metal layer 24 and the second layer 22, the film thickness of the second layer 22 in contact with the metal layer 24 is preferably greater than 10 nm. The film thickness of the first layer 20 and the second layer 22 which are not in contact with the semiconductor substrate 12 and the metal layer 24 is, for example, 5 nm.

[0022] use Figure 2 A method for manufacturing the semiconductor device 10 will be described.

[0023] First, if Figure 2 As shown in (a), the first layer 20 is formed on the semiconductor substrate 12. The semiconductor substrate 12 is placed in a chamber, and the first layer 20 is formed by using the ALD (Atomic Layer Deposition) method.

[0024] Next, if Figure 2 As shown in (b), the second layer 22 is formed on the first layer 20. In the same chamber as that for forming the first layer 20, the film forming material (precursor) is replaced and the film formation is continuously performed using the ALD method.

[0025] Next, if Figure 2 As shown in (c), the first layer 20 and the second layer 22 are alternately formed. In the same chamber as the first layer 20 and the second layer 22, the film forming materials (precursors) are replaced and the films are continuously formed using the ALD method.

[0026] Through the above steps, the adhesive layer 18 is formed. These steps of forming the adhesive layer 18 are collectively referred to as a first step.

[0027] Next, if Figure 2 As shown in (d), a metal layer 24 is formed on the second layer 22 formed last in the first step. This step is referred to as a second step. The metal layer 24 is formed by, for example, sputtering, vapor deposition, plating, or the like.

[0028] As described above, according to Embodiment 1, the first layer 20 is made of a material containing the elements constituting the semiconductor substrate 12. Therefore, the first layer 20 has high adhesion to the semiconductor substrate 12. Since the first layer 20 is in contact with the semiconductor substrate 12 in the adhesion layer 18, the adhesion layer 18 has high adhesion to the semiconductor substrate 12.

[0029] Furthermore, since the second layer 22 is made of a material having higher adhesion to the metal layer 24 than the first layer 20 , the adhesion between the adhesion layer 18 and the metal layer 24 is higher than when the adhesion layer 18 is a single layer structure consisting of only the first layer 20 .

[0030] Furthermore, since the adhesive layer 18 has a total of four or more first layers 20 and second layers 22, there are three or more interfaces in the adhesive layer 18. Therefore, even if stress is applied to the adhesive layer as when the semiconductor device warps, the stress does not concentrate on one interface.

[0031] In addition, among the first layer 20 and the second layer 22 constituting the adhesion layer 18, if the second layer 22 in contact with the metal layer 24 is removed, the first layer 20 in contact with the semiconductor substrate 12 has the thickest film thickness. Therefore, the components of the second layer 22 located above the first layer 20 in contact with the semiconductor substrate 12 are prevented from moving through the first layer 20 to the vicinity of the interface with the semiconductor substrate 12 due to diffusion or the like. Therefore, the adhesion between the semiconductor substrate 12 and the adhesion layer 18 is prevented from being reduced. In addition, if the first layer 20 in contact with the semiconductor substrate 12 is removed, the second layer 22 in contact with the metal layer 24 has the thickest film thickness. Therefore, the components of the first layer 20 located below the second layer 22 in contact with the metal layer 24 are prevented from moving through the second layer 22 to the vicinity of the interface with the metal layer 24 due to diffusion or the like. Therefore, the adhesion between the metal layer 24 and the adhesion layer 18 is prevented from being reduced.

[0032] This shows that the adhesion between the semiconductor substrate 12 and the metal layer 24 is prevented from being reduced.

[0033] In addition, since the thickness of the layers other than the first layer 20 in contact with the semiconductor substrate 12 and the second layer 22 in contact with the metal layer 24 can be reduced, the thickness of the entire adhesion layer can be reduced. Therefore, the resistance of the adhesion layer in the thickness direction does not increase.

[0034] In addition, since the ALD method is used to continuously form the first layer 20 and the second layer 22 constituting the close contact layer 18 in the same chamber, the film thickness of the first layer 20 and the second layer 22 is uniform, the cleanliness of the interface between these layers is good, and the close contact in the close contact layer 18 is high. The film thickness becomes uniform because the ALD method with good film thickness control is used. The cleanliness of the interface between the first layer 20 and the second layer 22 is good because the film is continuously formed in the same chamber, and the semiconductor device will not be taken out of the chamber with many impurities during the film formation. In this way, the cleanliness of the interface between the first layer 20 and the second layer 22 is good, so the close contact in the close contact layer 18 is high.

[0035] Among them, a step of performing heat treatment at a temperature higher than the upper limit temperature of film formation when the first layer and the second layer are formed in the first step may be provided between the first step and the second step. In the ALD method, film formation cannot be performed at a temperature higher than the temperature at which the precursor decomposes in the gas phase (the upper limit temperature of film formation). If heat treatment is performed at a temperature higher than the upper limit temperature of film formation after the first step and before the second step, the adhesion in the adhesion layer 18 is improved through reactions and mutual diffusion between the layers in the adhesion layer 18. If heat treatment is continuously performed in the ALD device used in the first step, the cleanliness of the top surface of the adhesion layer 18 is improved. When the precursor is TMA (trimethylaluminum), the upper limit temperature of film formation is about 450°C.

[0036] In addition, although the first layer 20 and the second layer 22 are made of the same material in the adhesion layer 18, they do not have to be made of the same material. For example, a stacked structure may be formed such that the first layer 20 is made of Si or WSi and the second layer 22 is made of Ti or Ni, such as Si / Ti / Si / Ti / WSi / Ni / WSi / Ni from the bottom layer.

[0037] Although the first layer 20 and the second layer 22 are formed by ALD, sputtering, vapor deposition, CVD (Chemical Vapor Deposition), etc. can also be used to form the films. In this case, the effect of preventing the decrease in adhesion between the semiconductor substrate 12 and the metal layer 24 can also be achieved.

[0038] In addition, the metal layer 24 may be made of not only metal but also conductive materials such as alloys and polysilicon.

[0039] Implementation Method 2

[0040] A semiconductor device according to Embodiment 2 will be described. The semiconductor device according to Embodiment 2 differs from the semiconductor device 10 according to Embodiment 1 in that it includes a semiconductor substrate having a through hole formed therein. Including this point, the differences from Embodiment 1 will be mainly described here.

[0041] The structure of the semiconductor device according to the second embodiment is described. Figure 3 A semiconductor device 50 is shown. Figure 3 is a cross-sectional view of the semiconductor device 50 .

[0042] The semiconductor device 50 includes a semiconductor substrate 52. The semiconductor substrate 52 has a first surface 54 and a second surface 56 facing each other. The semiconductor substrate 52 is made of SiC, for example.

[0043] The semiconductor substrate 52 is provided with a through hole 68 penetrating from the first surface 54 to the second surface 56 .

[0044] An electrode 66 covering the through hole 68 is provided on the second surface 56 of the semiconductor substrate 52. The electrode 66 is made of, for example, Ti / Au.

[0045] The adhesive layer 58 is formed on the surface 70 of the electrode 66 facing the through hole 68, the side surface 72 of the through hole 68, and the first surface 54. The laminated structure in the adhesive layer 58 is the same as that of the adhesive layer 18 of the first embodiment. Figure 3 In the figure, the stacking structure in the adhesion layer 58 is omitted.

[0046] A metal layer 64 is formed on the adhesion layer 58. The metal layer 64 is made of, for example, Au.

[0047] Figure 4 Is magnification Figure 3 The area enclosed by the dotted line is shown in Figure 1. Figure 4 , the stacked structure in the adhesion layer 58 is depicted. The adhesion layer 58 is alternately stacked with the same number of first layers 60 and second layers 62 from the substrate 52 side toward the metal layer 64. Both the first layer 60 and the second layer 62 are conductive. The first layer 60 is composed of a material containing elements constituting the semiconductor substrate 52, such as Si. A material having a higher adhesion to the metal layer 64 than the first layer 60 is used for the second layer 62. The adhesion layer 58 may have a total of more than 4 layers of the first layer 60 and the second layer 62, preferably more than 6 layers. If the second layer 62 in contact with the metal layer 64 is removed, the film thickness of the first layer 60 in contact with the semiconductor substrate 12 is the thickest, and if the first layer 60 in contact with the semiconductor substrate 52 is removed, the film thickness of the second layer 62 in contact with the metal layer 64 is the thickest.

[0048] use Figure 5 A method for manufacturing the semiconductor device 50 will be described.

[0049] In the method for manufacturing the semiconductor device 50, first, Figure 5 As shown in (a) of FIG. 5 , an electrode 66 is formed on the second surface 56 of the semiconductor substrate 52. The electrode 66 is formed by, for example, sputtering, vapor deposition, plating, or the like.

[0050] Next, as shown in FIG. 5( b ), the semiconductor substrate 52 is etched from the first surface 54 side to the electrode 66 to form a through hole 68 .

[0051] Next, if Figure 5 As shown in (c), the adhesion layer 58 is formed on the surface 70 of the electrode 66 facing the through hole 68, the side surface 72 of the through hole 68, and the first surface 54. Figure 5 In (c), the illustration of the stacked structure in the adhesion layer 58 is omitted, but the adhesion layer 58 is similar to the adhesion layer 18 of the first embodiment, and is formed by alternately stacking the first layer 60 and the second layer 62 from the semiconductor substrate 52 side. The stacking is continuously performed in the same chamber using the ALD method. The process of forming the adhesion layer 58 is referred to as the first process.

[0052] Next, if Figure 5 As shown in (d), a metal layer 64 is formed on the adhesion layer 58, that is, on the second layer 62 formed last in the first step. This step is referred to as the second step. The metal layer 64 is formed by, for example, sputtering, vapor deposition, plating, or the like.

[0053] As described above, according to Embodiment 2, the same effect as Embodiment 1 is obtained. In particular, when a SiC substrate is used as the semiconductor substrate 52 and a high-frequency device using gallium nitride (GaN) is formed on the second surface 56 side of the semiconductor substrate 52, the adhesion between the semiconductor substrate 52 and the metal layer 64 may be reduced, so the application of this embodiment is effective in preventing the reduction of adhesion.

[0054] Description of Reference Numerals

[0055] 10, 50...semiconductor device; 12, 52...semiconductor substrate; 14, 54...first surface; 16, 56...second surface; 18, 58...adhesion layer; 20, 60...first layer; 22, 62...second layer; 24, 64...metal layer; 66...electrode; 68...through hole; 70...face; 72...side surface.

Claims

1. A semiconductor device, wherein: The semiconductor device comprises: A semiconductor substrate having a first surface and a second surface facing each other; a close contact layer, formed by alternately stacking the same number of first layers and second layers both having conductivity on the first surface; and A metal layer is formed on the close contact layer, The first layer is composed of a material containing an element constituting the semiconductor substrate, The second layer has higher adhesion to the metal layer than the first layer. The adhesion layer includes a total of four or more first layers and second layers, Among the first layer and the second layer constituting the adhesion layer, if the second layer in contact with the metal layer is removed, the first layer in contact with the semiconductor substrate has the thickest film thickness, and if the first layer in contact with the semiconductor substrate is removed, the second layer in contact with the metal layer has the thickest film thickness.

2. The semiconductor device according to claim 1, wherein The first layer in contact with the semiconductor substrate and the second layer in contact with the metal layer both have a film thickness of 10 nm or more.

3. The semiconductor device according to claim 1 or 2, wherein: The semiconductor substrate is provided with a through hole penetrating from the first surface to the second surface, An electrode covering the through hole is provided on the second surface, The adhesion layer is formed on a surface of the electrode facing the through hole, a side surface of the through hole, and the first surface.

4. A method for manufacturing a semiconductor device, wherein: The following processes are available: In a first step, an equal number of first layers and second layers, both of which have conductivity, are formed alternately in sequence on a semiconductor substrate; and In a second step, a metal layer is formed on the second layer formed last in the first step. The first layer is composed of a material containing an element constituting the semiconductor substrate, The second layer has higher adhesion to the metal layer than the first layer. In the first step, a total of four or more layers of the first layer and the second layer are continuously formed in the same chamber using an ALD method. Of the first layer and the second layer formed in the first process, if the second layer in contact with the metal layer is removed, the first layer in contact with the semiconductor substrate has the thickest film thickness, and if the first layer in contact with the semiconductor substrate is removed, the second layer in contact with the metal layer has the thickest film thickness.

5. The method for manufacturing a semiconductor device according to claim 4, wherein: A step of performing heat treatment at a temperature higher than an upper limit temperature of film formation when the first layer and the second layer are formed in the first step is provided between the first step and the second step.

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