Method for manufacturing an electronic device

Abstract

To provide a method of manufacturing an electronic device that can suppress a graphene layer from deforming during transfer.SOLUTION: A method of manufacturing an electronic device has: the processes of: growing a graphene layer on a first substrate; bringing a retainer into contact with the graphene layer; peeling the laminate structure of the graphene layer and the retainer from the first substrate; forming a volatile liquid film on a second substrate; placing the laminate structure on the liquid film with the graphene layer in contact with the liquid film; vaporizing the liquid film to bring the graphene layer into contact with the second substrate; and removing the retainer after bringing the graphene layer into contact with the second substrate.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing an electronic device.

Background Art

[0002] Conventionally, when manufacturing an electronic device including graphene provided on a substrate, a graphene layer is grown on a growth substrate and the graphene layer is transferred onto the substrate. At the time of transfer, the graphene layer is held by a holder such as polymethyl methacrylate (PMMA), the holder holding the graphene layer is floated on the water surface, the holder is scooped up with the substrate, and then the holder is dissolved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since the laminated structure of the graphene layer and the holder is thin and flexible, it is easily deformed. For this reason, when the holder is scooped up with the substrate, wrinkles may occur in the graphene layer or cracks may occur due to the action of an external force. Also, water may remain between the graphene layer and the substrate. That is, deformation may occur in the graphene layer during the transfer of the graphene layer.

[0005] An object of the present disclosure is to provide a method for manufacturing an electronic device capable of suppressing deformation of a graphene layer during transfer. **Means for Solving the Problems**

[0006] According to one aspect of the present disclosure, there is provided a method for manufacturing an electronic device, the method including: growing a graphene layer on a first substrate; bringing a holding body into close contact with the graphene layer; peeling a laminate structure of the graphene layer and the holding body from the first substrate; forming a liquid film having volatility on a second substrate; placing the laminate structure on the liquid film such that the graphene layer contacts the liquid film; By volatilization vaporizing the liquid film to bring the graphene layer into contact with the second substrate; and removing the holding body after bringing the graphene layer into contact with the second substrate. **Advantages of the Invention**

[0007] According to the present disclosure, deformation of the graphene layer during transfer can be suppressed. **Brief Description of the Drawings**

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be specifically described with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration may be denoted by the same reference numerals, and redundant descriptions may be omitted.

[0010] (First Embodiment) First, the first embodiment will be described. FIGS. 1 to 9 are cross-sectional views showing a method for manufacturing an electronic device according to the first embodiment.

[0011] First, as shown in FIG. 1, a first substrate 10 is prepared. The first substrate 10 includes, for example, a sapphire substrate 11 and a catalyst film 12 formed on the sapphire substrate 11. The catalyst film 12 is, for example, a Cu film having a mirror index of (111) on the surface.

[0012] Next, as shown in FIG. 2, a graphene layer 31 is grown on the catalyst film 12. The graphene layer 31 is composed of a single layer of graphene or two or more layers of graphene stacked on each other. The graphene layer 31 can be grown, for example, by a chemical vapor deposition (CVD) method.

[0013] Thereafter, as shown in FIG. 3, a holder 32 is brought into close contact with the graphene layer 31. For example, the holder 32 contains PMMA. The holder 32 can be formed to be in close contact with the graphene layer 31, for example, by applying a PMMA solution onto the graphene layer 31 and performing a baking process after the application.

[0014] Subsequently, as shown in FIG. 4, a laminate structure 33 of the graphene layer 31 and the holder 32 is peeled off from the first substrate 10. In the peeling of the laminate structure 33, for example, the catalyst film 12 is dissolved. When the catalyst film 12 is a Cu film, for example, the catalyst film 12 can be removed using an aqueous silver nitrate solution. The thickness of the laminate structure 33 is, for example, 0.5 μm or less, and the laminate structure 33 has flexibility.

[0015] Further, as shown in FIG. 5, separately prepare a second substrate 20, and form a volatile liquid film 23 on the second substrate 20. The second substrate 20 has, for example, an Si substrate 21 and an Si oxide film 22 formed on the surface of the Si substrate 21. The Si substrate 21 may be conductive. The liquid film 23 contains, for example, n-heptane. The liquid film 23 can be formed, for example, by dropping a liquid containing n-heptane.

[0016] Then, as shown in FIG. 6, place the laminated structure 33 on the liquid film 23 such that the graphene layer 31 contacts the liquid film 23. Since the laminated structure 33 has flexibility, when the laminated structure 33 is placed on the liquid film 23, it spreads on the liquid film 23 due to the surface tension of the liquid film 23.

[0017] Next, as shown in FIG. 7, vaporize the liquid film 23 by volatilization to bring the graphene layer 31 into contact with the second substrate 20. When the liquid film 23 contains n-heptane, the liquid film 23 can be vaporized by maintaining at room temperature. As the vaporization of the liquid film 23 progresses, the graphene layer 31 approaches the second substrate 20. Also, while the vaporization is progressing, the external force in the direction parallel to the surface of the second substrate 20 acting on the laminated structure 33 is substantially only the surface tension of the liquid film 23. Therefore, when the vaporization is completed, the graphene layer 31 contacts the second substrate 20 in a state where substantially no wrinkles exist.

[0018] Thereafter, as shown in FIG. 8, fix the graphene layer 31 to the second substrate 20 by heat treatment. The temperature of the heat treatment is, for example, about 80°C to 180°C. The temperature of the heat treatment is preferably a temperature at which the holder 32 does not deteriorate.

[0019] Subsequently, as shown in FIG. 9, remove the holder 32. When the holder 32 contains PMMA, for example, the holder 32 can be removed using acetone. Thereafter, if necessary, perform processing of the graphene layer 31, formation of electrodes, formation of wiring, etc. For example, form a source electrode and a drain electrode.

[0020] In this way, an electronic device including the graphene layer 31 can be manufactured. For example, when the Si substrate 21 has conductivity, a transistor having the Si substrate 21 as a back gate can be configured.

[0021] In the first embodiment, the liquid film 23 is vaporized by volatilization to bring the graphene layer 31 into contact with the second substrate 20. Therefore, during the transfer, the shape of the laminated structure 33 spread by the surface tension of the liquid film 23 can be maintained. Accordingly, deformation of the graphene layer 31 included in the laminated structure 33 can be suppressed.

[0022] (Second Embodiment) Next, the second embodiment will be described. FIGS. 10 to 15 are cross-sectional views showing a method for manufacturing an electronic device according to the second embodiment.

[0023] First, as shown in FIG. 10, a second substrate 40 is prepared. The second substrate 40 has, for example, an Si substrate 21, an Si oxide film 22 formed on the surface of the Si substrate 21, and a three-dimensional structure 42 having a flow path 41 through which a gas flows. The three-dimensional structure 42 is provided on the Si oxide film 22 on one surface side of the Si substrate 21.

[0024] Next, as shown in FIG. 11, a volatile liquid film 23 is formed on the surface of the second substrate 40 where the three-dimensional structure 42 is provided. The liquid film 23 can be formed, for example, by dropping a liquid containing n-heptane.

[0025] Separately, in the same manner as in the first embodiment, the process up to the peeling of the laminated structure 33 from the first substrate 10 is performed (see FIG. 4).

[0026] Then, as shown in FIG. 12, the laminated structure 33 is placed on the liquid film 23 so that the graphene layer 31 contacts the liquid film 23. Since the laminated structure 33 has flexibility, when the laminated structure 33 is placed on the liquid film 23, it spreads on the liquid film 23 due to the surface tension of the liquid film 23.

[0027] Next, as shown in FIG. 13, the liquid film 23 is vaporized by volatilization to bring the graphene layer 31 into contact with the second substrate 40. At this time, the gas generated by the vaporization of the liquid film 23 flows through the flow path 41. As the vaporization of the liquid film 23 progresses, the graphene layer 31 approaches the second substrate 40. Further, while the vaporization is in progress, the external force in the direction parallel to the surface of the second substrate 40 acting on the laminated structure 33 is substantially only the surface tension of the liquid film 23. Therefore, when the vaporization is completed, the graphene layer 31 contacts the second substrate 40 in a state where wrinkles are substantially absent.

[0028] Thereafter, as shown in FIG. 14, the graphene layer 31 is fixed to the second substrate 40 by heat treatment.

[0029] Subsequently, as shown in FIG. 15, the holder 32 is removed. When the holder 32 contains PMMA, for example, the holder 32 can be removed using acetone. Thereafter, processing of the graphene layer 31, formation of electrodes, formation of wirings, etc. are performed as necessary.

[0030] In this way, an electronic device including the graphene layer 31 can be manufactured.

[0031] Note that the three-dimensional structure 42 may include part or all of the semiconductor element. Here, an example of the three-dimensional structure 42 including part of the semiconductor element will be described. This example includes part of a transistor. FIG. 16 is a top view showing an example of the three-dimensional structure. FIG. 17 is a cross-sectional view showing an example of the three-dimensional structure. FIG. 17 corresponds to a cross-sectional view taken along line XVII-XVII in FIG. 16.

[0032] The three-dimensional structure 52 shown in FIGS. 16 and 17 has a half-gate electrode 61, a source wiring 62, a drain wiring 63, and a half-gate insulating film 64. The half-gate electrode 61, the source wiring 62, and the drain wiring 63 are formed on the SiO2 film 22. In plan view, the half-gate electrode 61 is located between the source wiring and the drain wiring 63. The half-gate insulating film 64 is formed on the SiO2 film 22 so as to cover the half-gate electrode 61, the source wiring 62, and the drain wiring 63. Openings 72 that expose a part of the upper surface of the source wiring 62 and openings 73 that expose a part of the upper surface of the drain wiring 63 are formed in the half-gate insulating film 64. For example, the materials of the half-gate electrode 61, the source wiring 62, and the drain wiring 63 are Au, and the material of the half-gate insulating film 64 is alumina (Al 2 O 3 ).

[0033] On the surface of the half-gate insulating film 64, irregularities following the half-gate electrode 61, the source wiring 62, and the drain wiring 63 exist, and the concave portions function as flow paths 41.

[0034] Next, a method for manufacturing a semiconductor device using the second substrate 40 including the three-dimensional structure 52 will be described. FIGS. 18 to 21 are cross-sectional views showing specific examples of the method for manufacturing a semiconductor device according to the second embodiment.

[0035] As shown in FIG. 18, a liquid film 23 is formed so as to cover the three-dimensional structure 52. The liquid film 23 enters the concave portions of the three-dimensional structure 52. Then, a stacked structure 33 is placed on the liquid film 23 such that the graphene layer 31 contacts the liquid film 23.

[0036] Thereafter, when the liquid film 23 vaporizes, the gas generated by the vaporization of the liquid film 23 flows through the concave portions of the three-dimensional structure 52 and is discharged. Then, when all of the liquid film 23 is removed, as shown in FIG. 19, the stacked structure 33 including the graphene layer 31 adheres to the second substrate 40 including the three-dimensional structure 52.

[0037] Subsequently, as shown in FIG. 20, the holder 32 is removed. Next, the graphene layer 31 is processed into the shape of the channel.

[0038] Thereafter, as shown in FIG. 21, the source electrode 82 and the drain electrode 83 are formed. The source electrode 82 is formed so as to contact the source wiring 62 through the opening 72 and also contact the end portion of the graphene layer 31 on the source wiring 62 side. The drain electrode 83 is formed so as to contact the drain wiring 63 through the opening 73 and also contact the end portion of the graphene layer 31 on the drain wiring 63 side. For example, the materials of the source electrode 82 and the drain electrode 83 are Au.

[0039] In this way, the semiconductor device can be manufactured. For example, if the Si substrate 21 contains impurities to have a low resistance, a transistor 50 can be configured with the Si substrate 21 as the back gate electrode and the Si oxide film 22 as the back gate insulating film. FIG. 22 is a top view showing the transistor 50. FIG. 21 corresponds to a cross-sectional view taken along the line XXI-XXI in FIG. 20. In FIG. 22, the half gate insulating film 64 is omitted.

[0040] Note that the material of the liquid film 23 is not limited, but the polarity of the liquid film 23 is preferably weak. This is to suppress the influence on the characteristics of semiconductor elements such as transistors when the components of the liquid film 23 remain. For example, the solubility parameter of the liquid film 23 is preferably 10 or less in terms of the SP value. Also, it is preferable that the holder 32 and the graphene layer 31 are insoluble in the liquid film 23. This is to prevent the holder 32 and the graphene layer 31 from dissolving before the transfer is completed. Also, the vaporization temperature of the liquid film 23 is preferably low. This is to make it easy to vaporize the liquid film 23. For example, the vaporization temperature of the liquid film 23 is preferably 100° C. or lower. The liquid film 23 preferably contains n-pentane, n-hexane, benzene, or any combination thereof.

[0041] When vaporizing the liquid film 23, the second substrate may be heated to a temperature at which the liquid film 23 does not boil to promote vaporization. In this case, the heating temperature may be, for example, 20 °C or lower than the vaporization temperature of the liquid film 23.

[0042] As described above, the preferred embodiments and the like have been described in detail. However, the present invention is not limited to the above-described embodiments and the like, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope described in the claims.

[0043] Hereinafter, aspects of the present disclosure will be summarized and described as appendices.

[0044] (Appendix 1) A step of growing a graphene layer on a first substrate; A step of bringing a holder into close contact with the graphene layer; A step of peeling the laminate of the graphene layer and the holder from the first substrate; A step of forming a volatile liquid film on a second substrate; A step of placing the laminate on the liquid film so that the graphene layer contacts the liquid film; A step of vaporizing the liquid film to bring the graphene layer into contact with the second substrate; A step of removing the holder after bringing the graphene layer into contact with the second substrate; A method for manufacturing an electronic device, comprising: (Appendix 2) The method for manufacturing an electronic device according to Appendix 1, wherein the solubility parameter of the liquid film is 10 or less in terms of SP value. (Appendix 3) The method for manufacturing an electronic device according to Appendix 1 or 2, wherein the vaporization temperature of the liquid film is 100 °C or lower. (Appendix 4) The method for manufacturing an electronic device according to any one of Appendices 1 to 3, wherein the liquid film contains n-pentane, n-hexane, benzene, or any combination thereof. (Appendix 5) The method for manufacturing an electronic device according to any one of Appendices 1 to 4, characterized by having a step of fixing the graphene layer to the second substrate by heat treatment between the step of bringing the graphene layer into contact with the second substrate and the step of removing the holding body. (Appendix 6) The step of vaporizing the liquid film includes a step of heating the second substrate. The method for manufacturing an electronic device according to any one of Appendices 1 to 5. (Appendix 7) The second substrate has a flow path on the surface where the liquid film is formed, through which the gas generated by vaporization of the liquid film flows. The method for manufacturing an electronic device according to any one of Appendices 1 to 6. (Appendix 8) The flow path includes a part or all of a semiconductor element. The method for manufacturing an electronic device according to Appendix 7. (Appendix 9) The holding body contains polymethyl methacrylate. The method for manufacturing an electronic device according to any one of Appendices 1 to 8.

Explanation of Reference Numerals

[0045] 10: First substrate 11: Sapphire substrate 12: Catalyst film 20, 40: Second substrate 21: Si substrate 22: Silicon oxide film 23: Liquid film 31: Graphene layer 32: Holding body 33: Laminated structure 41: Flow path 42, 52: Three-dimensional structure 50: Transistor

Claims

1. A step of growing a graphene layer on a first substrate; A step of bringing a holder into close contact with the graphene layer; A step of peeling the laminated structure of the graphene layer and the holder from the first substrate; A step of forming a liquid film having volatility on a second substrate; A step of placing the laminated structure on the liquid film so that the graphene layer contacts the liquid film; A step of vaporizing the liquid film by volatilization to bring the graphene layer into contact with the second substrate; A step of removing the holder after bringing the graphene layer into contact with the second substrate; A method for manufacturing an electronic device, comprising the above steps.

2. The method for manufacturing an electronic device according to claim 1, wherein the liquid film contains n-pentane, n-hexane, benzene, or any combination thereof.

3. The method for manufacturing an electronic device according to claim 1 or 2, further comprising a step of fixing the graphene layer to the second substrate by heat treatment between the step of bringing the graphene layer into contact with the second substrate and the step of removing the holder.

4. The method for manufacturing an electronic device according to any one of claims 1 to 3, wherein the step of vaporizing the liquid film includes a step of heating the second substrate to a temperature below the boiling temperature of the liquid film.

5. The method for manufacturing an electronic device according to any one of claims 1 to 4, wherein the second substrate has a flow path on the surface where the liquid film is formed, through which the gas generated by vaporization of the liquid film flows.

6. The method for manufacturing an electronic device according to claim 5, wherein the flow path includes a part or all of a semiconductor element.

Images