JP2017165642A - Substrate and electronic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate in which a high mobility can be stably ensured when manufacturing an electronic element in which the graphene film serves as a conductive part.SOLUTION: The substrate 1 includes: a support substrate 2 having a first main surface 2A and in which the surface layer region including at least said first main surface 2A is made of any one of material selected from the group consisting of boron nitride, molybdenum disulfide, tungsten disulfide, niobium disulfide and aluminum nitride; and a graphene film 3 disposed on the first main surface 2A and having an atomic arrangement oriented with respect to the atomic arrangement of the material constituting the surface layer region.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a substrate and an electronic device, and more particularly to a substrate and an electronic device including a graphene film.

Graphene is a substance in which carbon atoms form a sp ² hybrid orbital and are bonded in a plane. Due to such a carbon bonding state, graphene has a characteristic of having extremely high carrier mobility. Therefore, for example, the use of a graphene film as a channel of an electronic device such as a transistor is expected to increase the speed of the electronic device.

  By manufacturing a substrate including a graphene film and forming an electrode or the like on the substrate, an electronic element using the graphene film as a conductive portion (for example, a channel) can be manufactured. A substrate including a graphene film can be manufactured, for example, by attaching a graphene thin film peeled off from graphite to a supporting substrate, or by attaching a graphene thin film grown by chemical vapor deposition (CVD) to a supporting substrate. .

  In order to ensure acceptable production efficiency in mass production of electronic elements, it is preferable to employ a support substrate having a large diameter (for example, having a diameter of 2 inches or more) in the substrate. In the substrate manufactured by the procedure including the attachment of the graphene film as described above, there are many regions where the graphene film does not exist on the surface of the support substrate. In such a case, automation is hindered in the manufacturing process of the electronic device such as alignment of electrode formation. As a result, there arises a problem that mass production of electronic devices using the substrate is difficult.

  On the other hand, a method of obtaining a substrate in which a graphene film is formed on a support substrate by converting a surface layer portion of the substrate into graphene by heating a substrate made of SiC (silicon carbide) to release Si atoms is proposed. (For example, refer to Patent Document 1). Thereby, the area | region where a graphene film does not exist in the main surface of a board | substrate becomes small. As a result, mass production of electronic elements using the substrate is facilitated.

Japanese Patent Laying-Open No. 2015-48258

  However, when an electronic device having a graphene film as a conductive portion is manufactured using a substrate having a graphene film formed on a support substrate made of SiC, the mobility in the conductive portion is lower than expected. There is.

  Thus, it is an object of the present invention to provide a substrate capable of stably ensuring high mobility when an electronic element whose graphene film serves as a conductive portion is manufactured, and an electronic element including the substrate.

The substrate according to the present invention has a first main surface, and at least the surface layer region including the first main surface is boron nitride (BN), molybdenum disulfide (MoS ₂ ), tungsten disulfide (WS ₂ ), disulfide. A support substrate made of any one material selected from the group consisting of niobium (NbS ₂ ) and aluminum nitride (AlN), and an atomic arrangement of the material arranged on the first main surface and constituting the surface layer region And a graphene film having an oriented atomic arrangement.

  According to the said board | substrate, when manufacturing the electronic device by which a graphene film becomes an electroconductive part, a high mobility can be ensured stably.

3 is a schematic cross-sectional view illustrating a structure of a substrate including a graphene film in Embodiment 1. FIG. It is a flowchart which shows the outline of the manufacturing method of the board | substrate containing a graphene film. FIG. 3 is a schematic cross sectional view for illustrating the method for manufacturing the substrate in the first embodiment. It is a schematic sectional drawing which shows the structure of a heating apparatus. 7 is a schematic cross-sectional view illustrating a structure of a substrate including a graphene film in Embodiment 2. FIG. FIG. 10 is a schematic cross sectional view for illustrating the method for manufacturing the substrate in the second embodiment. It is a schematic sectional drawing which shows the structure of the field effect transistor (FET) containing a graphene film. It is a flowchart which shows the outline of the manufacturing method of the field effect transistor containing a graphene film. It is a schematic sectional drawing for demonstrating the manufacturing method of the field effect transistor containing a graphene film. It is a schematic sectional drawing for demonstrating the manufacturing method of the field effect transistor containing a graphene film. It is a schematic sectional drawing for demonstrating the manufacturing method of the field effect transistor containing a graphene film.

[Description of Embodiment of Present Invention]
First, embodiments of the present invention will be listed and described. The substrate of the present application has a first main surface, and the surface layer region including at least the first main surface is boron nitride (BN), molybdenum disulfide (MoS ₂ ), tungsten disulfide (WS ₂ ), niobium disulfide (NbS). ₂ ) and a support substrate made of any one material selected from the group consisting of aluminum nitride (AlN), and atoms arranged on the first main surface and oriented with respect to the atomic arrangement of the material constituting the surface layer region And a graphene film having an array.

In the case where an electronic device in which a graphene film is a conductive part is manufactured using a substrate in which a graphene film is formed on a support substrate made of SiC, the inventors have compared the expected mobility in the conductive part. The cause of the decrease was investigated. As a result, in the graphene film having an atomic arrangement oriented with respect to the SiC atomic arrangement constituting the support substrate, there is a region where the graphene film thickness is partially increased, and the presence of the region greatly affects the mobility. I found out. Further, not on the support substrate made of SiC, but on the support substrate made of any one material selected from the group consisting of BN, MoS ₂ , WS ₂ , NbS ₂ and AlN, at least the surface layer region including the first main surface. In addition, the inventors have clarified that the formation of a graphene film having an atomic arrangement oriented with respect to the atomic arrangement of the material constituting the surface layer region can suppress the formation of a region having a large graphene film thickness. became.

In the substrate of the present application, the surface region including at least the first main surface is on the first main surface of the support substrate made of any one material selected from the group consisting of BN, MoS ₂ , WS ₂ , NbS ₂ and AlN. In addition, a graphene film having an atomic arrangement oriented with respect to the atomic arrangement of the material constituting the surface layer region is formed. Therefore, formation of a region having a large thickness in the graphene film can be suppressed. As a result, according to the substrate of the present application, it is possible to provide a substrate capable of stably ensuring high mobility when an electronic element having a graphene film as a conductive portion is manufactured.

  In the substrate, the graphene film may cover 80% or more of the first main surface. By doing in this way, the area | region where a graphene film does not exist in the 1st main surface of a support substrate becomes small. As a result, mass production of electronic devices using the substrate is facilitated.

In the substrate, the carrier mobility of graphene film is preferably 5000 cm ² / Vs or more, more preferably 8000 cm ² / Vs or more. By doing in this way, the speed-up of the electronic device manufactured using the said board | substrate can be achieved.

  In the substrate, the surface layer region may be made of boron nitride. Boron nitride is particularly suitable as a material constituting the surface layer region.

  In the substrate, the support substrate may include a base substrate and a support layer that is disposed on the base substrate and is made of a material different from that of the base substrate and includes the first main surface. The support layer may be the surface layer region. Even when a supporting substrate having such a structure is employed, it is possible to provide a substrate that can stably ensure high mobility when an electronic element in which a graphene film serves as a conductive portion is manufactured.

  In the substrate, the graphene film may have an atomic arrangement in which a region having an area ratio of 20% or more in plan view is oriented with respect to an atomic arrangement of a material constituting the surface layer region. By doing so, it is possible to more reliably provide a substrate that can stably ensure high mobility when an electronic element in which the graphene film becomes a conductive portion is manufactured.

  In the substrate, the support substrate may have a disk shape. The support substrate may have a diameter of 50 mm or more. By doing in this way, the efficiency improvement of the electronic device using the said board | substrate can be achieved.

  The electronic device of the present application is disposed such that the substrate, the first electrode disposed on the exposed surface that is the main surface opposite to the support substrate side of the graphene film, and the first electrode are separated on the exposed surface. A second electrode.

  In the electronic device of the present application, the first electrode and the second electrode are formed on the exposed surface of the substrate of the present application. Therefore, according to the electronic device of the present application, it is possible to stably ensure high mobility in the conductive portion.

[Details of the embodiment of the present invention]
Next, an embodiment of a substrate according to the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
Referring to FIG. 1, a substrate 1 in the present embodiment includes a support substrate 2 and a graphene film 3. The support substrate 2 is made of BN. The BN constituting the support substrate 2 is hexagonal BN. That is, the support substrate 2 is a hexagonal BN bulk substrate. The support substrate 2 has a disk shape. The diameter of the support substrate 2 is 2 inches or more (50 mm or more). The support substrate 2 has a first main surface 2A. The first main surface 2A is a main surface having an angle of 1 ° or less with the c-plane ({0001} plane). On the first main surface 2A, a crystal plane in which atoms are present at positions corresponding to the vertices of the hexagon is exposed. The c-plane of hexagonal BN is exposed on the first main surface 2A.

  The graphene film 3 is disposed on the first main surface 2 </ b> A of the support substrate 2. The graphene film 3 has an exposed surface 3A that is a main surface opposite to the support substrate 2 side. The graphene film 3 is made of graphene having an atomic arrangement oriented with respect to the atomic arrangement of BN constituting the support substrate 2. Here, the state in which the atomic arrangement of graphene constituting the graphene film 3 is oriented with respect to the atomic arrangement of BN constituting the supporting substrate 2 has a certain relationship between the atomic arrangement of graphene and the atomic arrangement of BN. It means having. Whether or not the atomic arrangement of graphene is oriented with respect to the atomic arrangement of BN can be confirmed by, for example, the LEED (Low Energy Electron Diffraction) method.

  In the substrate 1 of the present embodiment, the graphene film 3 having an atomic arrangement oriented with respect to the atomic arrangement of the material constituting the support substrate 2 is formed on the first main surface 2A from which the c-plane of hexagonal BN is exposed. Has been. Therefore, formation of a region having a large film thickness in the graphene film 3 is suppressed. As a result, the substrate 1 is a substrate capable of stably ensuring high mobility when an electronic element in which the graphene film 3 is a conductive portion is manufactured.

  The graphene film 3 preferably covers 80% or more of the first main surface 2A of the support substrate 2 in area ratio. Thereby, the area | region where the graphene film 3 does not exist in 2 A of 1st main surfaces of the support substrate 2 becomes small. As a result, mass production of electronic devices using the substrate 1 is facilitated.

The carrier mobility of the graphene film 3 is preferably not 5000 cm ² / Vs or more, more preferably 8000 cm ² / Vs or more. By doing in this way, the speed-up of the electronic device manufactured using the board | substrate 1 can be achieved.

  In addition, the graphene film 3 preferably has an atomic arrangement in which a region with an area ratio of 20% or more in plan view is oriented with respect to the atomic arrangement of the material constituting the support substrate 2. Thereby, when an electronic device in which the graphene film 3 serves as a conductive portion is manufactured, high mobility can be reliably ensured stably.

  Next, an outline of a method for manufacturing the substrate 1 in the present embodiment will be described with reference to FIGS.

  Referring to FIG. 2, in the method for manufacturing substrate 1 in the present embodiment, a substrate preparation step is first performed as a step (S10). Referring to FIG. 3, in this step (S10), substrate 11 made of hexagonal BN having a diameter of 2 inches (50.8 mm), for example, is prepared. More specifically, the substrate 11 made of BN is obtained by slicing an ingot made of BN. After the surface of the substrate 11 is polished, a substrate 11 in which the flatness and cleanliness of the main surface is ensured is obtained through a process such as cleaning. The substrate 11 has a first main surface 11A. 11A of 1st main surfaces are the main surfaces whose angle formed with c surface of BN which comprises the board | substrate 11, ie, {0001} surface, is 1 degrees or less. That is, the first main surface 11A is substantially a c-plane.

  Next, a silicon carbide film forming step is performed as a step (S20). Referring to FIG. 3, in this step (S <b> 20), SiC film 12 made of silicon carbide is formed on first main surface 11 </ b> A of substrate 11. Specifically, SiC film 12 is formed on first main surface 11A of substrate 11 by sputtering, for example. The SiC film 12 is made of, for example, amorphous or polycrystalline SiC. The thickness of SiC film 12 can be, for example, not less than 0.5 nm and not more than 5 nm. By performing step (S20), raw material substrate 10 including substrate 11 and SiC film 12 formed on first main surface 11A of substrate 11 is obtained.

  Next, a grapheneization process is implemented as process (S30). This step (S30) can be performed using, for example, a heating apparatus shown in FIG. With reference to FIG. 4, the heating device 90 includes a main body 91, a susceptor 92, a cover member 93, a gas introduction pipe 95, and a gas discharge pipe 96.

  The main body 91 includes a side wall 91B having a hollow cylindrical shape, a bottom wall 91A that closes the first end of the side wall 91B, and an upper wall 91C that closes the second end of the side wall 91B. Including. A susceptor 92 is disposed on the bottom wall 91 </ b> A inside the main body 91. The susceptor 92 has a substrate holding surface 92 </ b> A for holding the raw material substrate 10.

  A cover member 93 for covering the susceptor 92 is disposed inside the main body 91. The cover member 93 has, for example, a hollow cylindrical shape in which one end of a pair of ends is closed and the other end is open. The cover member 93 is arranged so that the other end side of the cover member 93 is in contact with the bottom wall portion 91A. The susceptor 92 and the raw material substrate 10 on the susceptor 92 are surrounded by the cover member 93 and the bottom wall portion 91 </ b> A of the main body portion 91. The susceptor 92 and the raw material substrate 10 on the susceptor 92 are arranged in a closed space 93C that is a space surrounded by the cover member 93 and the bottom wall portion 91A of the main body 91. The inner wall surface 93A of the cover member 93 and the main surface 12A opposite to the substrate 11 of the SiC film 12 of the raw material substrate 10 face each other (see FIG. 3).

  The gas introduction pipe 95 and the gas discharge pipe 96 are connected to the upper wall portion 91 </ b> C of the main body portion 91. The gas introduction pipe 95 and the gas discharge pipe 96 are connected at one end to a through hole formed in the upper wall portion 91C. The other end of the gas introduction pipe 95 is connected to a gas holding unit (not shown) that holds an inert gas. In the present embodiment, argon is held in the gas holding unit. The other end of the gas exhaust pipe 96 is connected to an exhaust device (not shown) such as a pump.

  A process (S30) can be implemented as follows using the heating apparatus 90. FIG. First, the raw material substrate 10 prepared in the step (S20) is disposed on the substrate holding surface 92A of the susceptor 92. Next, the cover member 93 is disposed on the bottom wall portion 91 </ b> A so as to cover the susceptor 92 and the raw material substrate 10. Thereby, the susceptor 92 and the raw material substrate 10 on the susceptor 92 are surrounded by the cover member 93 and the bottom wall portion 91 </ b> A of the main body portion 91.

  Next, the valve installed in the gas exhaust pipe 96 is opened while the valve (not shown) installed in the gas introduction pipe 95 is closed. Then, when the exhaust device connected to the gas exhaust pipe 96 is activated, the gas inside the main body 91 is exhausted from the gas exhaust pipe 96 along the arrow B. Thereby, the inside of the main body 91 is decompressed. Here, although the susceptor 92 and the raw material substrate 10 are surrounded by the cover member 93 and the bottom wall portion 91A of the main body 91, the cover member 93 and the bottom wall portion 91A are not joined. Therefore, when the pressure reduction in the main body portion 91 proceeds, the internal gas is discharged from a slight gap between the cover member 93 and the bottom wall portion 91A due to a pressure difference between the inside and the outside of the closed space 93C. As a result, the closed space 93C is also decompressed.

  Next, the operation of the exhaust device is stopped, and the valve installed in the gas introduction pipe 95 is opened. Thereby, the argon currently hold | maintained at the gas holding part is introduce | transduced into the inside of the main-body part 91 through the gas introduction pipe | tube 95 (arrow A). Here, when the pressure in the main body portion 91 rises, argon enters the inside through a slight gap between the cover member 93 and the bottom wall portion 91A due to a pressure difference between the inside and the outside of the closed space 93C. In this way, the gas inside the main body 91 is replaced with argon. When the pressure of argon inside the main body portion 91 rises to normal pressure (atmospheric pressure), surplus argon is discharged from the gas discharge pipe 96, whereby the internal pressure is maintained at normal pressure. That is, the inside of the main body 91 is maintained in a normal pressure argon atmosphere.

  Next, the raw material substrate 10 is heated. The raw material substrate 10 is heated by heating the main body 91, for example. The main body 91 may be heated by induction heating, for example. The raw material substrate 10 is heated to a temperature of 1300 ° C. or higher and 1800 ° C. or lower in, for example, argon at normal pressure. Thereby, referring to FIG. 3, Si atoms are separated from SiC constituting SiC film 12, and the surface layer portion of SiC film 12 which is a region including main surface 12A opposite to substrate 11 is converted into graphene. The On the other hand, main surface 12 </ b> B on the substrate 11 side of SiC film 12 is in contact with substrate 11. Therefore, the atomic arrangement in the region including the main surface 12B is oriented with respect to the atomic arrangement of BN constituting the substrate 11 by the heating. As a result, the atomic arrangement of graphene generated by the conversion of the SiC film 12 is oriented with respect to the atomic arrangement of BN constituting the substrate 11. Thus, referring to FIG. 1, support substrate 2 made of BN and atoms arranged on first main surface 2A of support substrate 2 and oriented with respect to the atomic arrangement of BN constituting support substrate 2 A substrate 1 including a graphene film 3 having an array is obtained.

  The substrate 1 in the present embodiment is completed by the above procedure. As described above, the cover member 93 is employed in the present embodiment. For this reason, the Si atoms detached from the SiC film 12 stay in the closed space 93C. As a result, the vapor pressure of Si in the closed space 93 </ b> C increases due to the separation of Si from the SiC film 12. Thereby, rapid conversion of SiC into graphene is suppressed. Thus, the graphene film 3 having one atomic layer or a small number of atomic layers (close to one atomic layer) is formed by suppressing the conversion rate to graphene.

  In addition, the region where the graphene film thickness that affects the lowering of mobility is large is formed corresponding to a region where defects on the surface of the substrate 11 or damage during substrate fabrication exist. In contrast, in the present embodiment, the surface layer portion of the prepared substrate 11 is not converted to graphene, but the SiC film 12 formed on the substrate 11 is converted to graphene. Therefore, even when a defect or damage exists in the surface layer portion of the substrate 11, it is possible to suppress the formation of a region having a large graphene film thickness due to these defects. As a result, it is possible to obtain the substrate 1 that can stably ensure high mobility.

(Embodiment 2)
Next, a second embodiment which is another embodiment of the substrate of the present application will be described. Referring to FIG. 5, substrate 1 of the second embodiment has basically the same structure as that of the first embodiment, and has the same effects. However, the substrate 1 of the second embodiment is different from the first embodiment in the structure of the support substrate 2.

  Referring to FIG. 5, support substrate 2 in the second embodiment is formed on carbon substrate 21 as a base substrate made of, for example, carbon (graphite), and one main surface 21A of carbon substrate 21, and is made of BN. And a BN film 22 as a support layer. BN constituting the BN film 22 that is the surface layer region is hexagonal BN. The BN film 22 can be formed on one main surface 21A of the carbon substrate 21 by, for example, CVD (Chemical Vapor Deposition). The thickness of the BN film 22 can be, for example, not less than 0.1 nm and not more than 1 mm. The support substrate 2 has a first main surface 2A. The first main surface 2A (the main surface 22A opposite to the carbon substrate 21 of the BN film 22) is a main surface having an angle of 1 ° or less with the c-plane ({0001} plane). On the first main surface 2A, a crystal plane in which atoms are present at positions corresponding to the vertices of the hexagon is exposed. The c-plane of hexagonal BN is exposed on the first main surface 2A. In the support substrate 2, the surface layer region including the first main surface 2A is made of BN.

  The graphene film 3 is disposed on the first main surface 2 </ b> A of the support substrate 2. The graphene film 3 is made of graphene having an atomic arrangement oriented with respect to the atomic arrangement of BN constituting the BN film 22 (surface layer region of the support substrate 2). Here, the state in which the atomic arrangement of graphene constituting the graphene film 3 is oriented with respect to the atomic arrangement of BN constituting the supporting substrate 2 has a certain relationship between the atomic arrangement of graphene and the atomic arrangement of BN. It means having. Whether or not the atomic arrangement of graphene is oriented with respect to the atomic arrangement of BN can be confirmed by, for example, the LEED (Low Energy Electron Diffraction) method.

  In the substrate 1 of the present embodiment, the orientation of the BN film 22 on the main surface 22A opposite to the carbon substrate 21 where the c-plane of hexagonal BN is exposed is oriented with respect to the atomic arrangement of the material constituting the BN film 22. A graphene film 3 having an atomic arrangement is formed. Therefore, formation of a region having a large film thickness in the graphene film 3 is suppressed. As a result, the substrate 1 is a substrate capable of stably ensuring high mobility when an electronic element in which the graphene film 3 is a conductive portion is manufactured.

  The substrate 1 of the second embodiment can be manufactured by the following procedure.

  Referring to FIG. 2, in the method for manufacturing substrate 1 in the second embodiment, a substrate preparation step is first performed as a step (S10). Referring to FIG. 6, this step (S10) has a structure in which, for example, BN film 112 made of hexagonal BN is formed on one main surface 111A of carbon substrate 111 having a diameter of 2 inches (50.8 mm). A substrate 11 is prepared. More specifically, a BN film 112 made of hexagonal BN is formed on one main surface 111A of the carbon substrate 111 by, for example, CVD. Thereby, the substrate 11 is obtained. The substrate 11 has a first main surface 11A. The first main surface 11A is a main surface having an angle of 1 ° or less with respect to the c-plane of BN constituting the BN film 112, that is, the {0001} plane. That is, the first main surface 11A is substantially a c-plane.

  Next, a silicon carbide film forming step is performed as a step (S20). This step (S20) is performed in the same manner as in the first embodiment. Thereby, raw material substrate 10 including substrate 11 and SiC film 12 formed on first main surface 11A of substrate 11 is obtained.

  Next, a grapheneization process is implemented as process (S30). Step (S30) is performed in the same manner as in Embodiment 1 using heating device 90. Thereby, referring to FIG. 6, Si atoms are separated from SiC constituting SiC film 12, and the surface layer portion of SiC film 12 which is a region including main surface 12A opposite to substrate 11 is converted into graphene. The On the other hand, main surface 12 </ b> B on the substrate 11 side of SiC film 12 is in contact with substrate 11. Therefore, the atomic arrangement of the region including the main surface 12B is oriented with respect to the atomic arrangement of BN constituting the BN film 112 by the heating. As a result, the atomic arrangement of graphene generated by the conversion of the SiC film 12 is oriented with respect to the atomic arrangement of BN constituting the BN film 112. In this way, referring to FIG. 5, the surface layer region including first main surface 2A is arranged on support substrate 2 made of BN and first main surface 2A of support substrate 2, and constitutes BN film 22. A substrate 1 including a graphene film 3 having an atomic arrangement oriented with respect to the atomic arrangement of BN is obtained. According to the above procedure, the substrate 1 of the second embodiment having the same effect as that of the first embodiment can be obtained.

Although the case where the support substrate 2 is made of BN has been described in the first embodiment, the support substrate 2 may be made of MoS ₂ , WS ₂ , NbS _2, or AlN. In the second embodiment, the case where the BN film 22 is formed on the carbon substrate 21 has been described. However, a MoS ₂ film, a WS ₂ film, an NbS ₂ film, or an AlN film is used instead of the BN film 22. May be. At this time, on the first main surface 2A, a crystal plane in which atoms are present at positions corresponding to the vertices of the hexagon is exposed. Such a substrate 1 can be manufactured by adopting MoS ₂ , WS ₂ , NbS ₂ or AlN instead of BN in the above embodiment. In the second embodiment, the case where the carbon substrate 21 is employed as the base substrate of the support substrate 2 has been described. However, the base substrate is not limited to this, and a boron nitride (BN) substrate, silicon carbide (SiC) is used. Substrate, silicon nitride (Si ₃ N ₄ ) substrate, aluminum nitride (AlN) substrate, alumina (Al ₂ O ₃ ) substrate, molybdenum (Mo) substrate, tungsten (W) substrate, tantalum (Ta) substrate, molybdenum carbide (MoC) A substrate, a tantalum carbide (TaC) substrate, a tungsten carbide (WC) substrate, or the like can be employed.

(Embodiment 3)
Next, a field effect transistor (FET) that is an example of an electronic element manufactured using the substrate 1 of the first embodiment will be described. Referring to FIG. 7, FET 9 in the present embodiment is manufactured using substrate 1 in the first embodiment, and support substrate 2 and graphene film laminated in the same manner as in the first embodiment. 3 is provided. The FET 9 further includes a source electrode 4 as a first electrode, a drain electrode 5 as a second electrode, a gate electrode 7 as a third electrode, and a gate insulating film 6.

  The source electrode 4 is formed in contact with the exposed surface 3A. The source electrode 4 is made of a conductor capable of making ohmic contact with the graphene film 3, for example, Ni (nickel) / Au (gold). The drain electrode 5 is formed in contact with the exposed surface 3A. The drain electrode 5 is formed away from the source electrode 4. The drain electrode 5 is made of a conductor capable of making ohmic contact with the graphene film 3, for example, Ni / Au.

A gate insulating film 6 is formed so as to cover the exposed surface 3A of the graphene film 3 located between the source electrode 4 and the drain electrode 5. The gate insulating film 6 covers the exposed surface 3A located between the source electrode 4 and the drain electrode 5, and is the upper surface of the source electrode 4 and the drain electrode 5 (the main surface opposite to the side in contact with the graphene film 3). It extends to the area covering a part of the surface. The gate insulating film 6 is made of an insulator such as silicon nitride (SiN) or aluminum oxide (Al ₂ O ₃ ).

  The gate electrode 7 is disposed so as to be in contact with the gate insulating film 6. The gate electrode 7 is disposed in a region corresponding to the exposed surface 3 </ b> A located between the source electrode 4 and the drain electrode 5. The gate electrode 7 is made of a conductor, for example, Ni / Au.

  In this FET 9, when the voltage applied to the gate electrode 7 is less than the threshold voltage, that is, when the FET 9 is OFF, the graphene film 3 positioned between the source electrode 4 and the drain electrode 5 (channel region) has no carrier. There are not enough electrons to be present, and the non-conductive state is maintained even when a voltage is applied between the source electrode 4 and the drain electrode 5. On the other hand, when a voltage equal to or higher than the threshold voltage is applied to the gate electrode 7 and the FET 9 is turned on, electrons serving as carriers are generated in the channel region. As a result, the source electrode 4 and the drain electrode 5 are electrically connected by the channel region in which electrons serving as carriers are generated. When a voltage is applied between the source electrode 4 and the drain electrode 5 in such a state, a current flows between the source electrode 4 and the drain electrode 5.

Here, in the FET 9 of the present embodiment, the source electrode 4 and the drain electrode 5 are formed on the exposed surface 3A of the substrate 1 described in the first embodiment. Therefore, high mobility is stably secured in the graphene film 3 corresponding to the channel region as the conductive portion. As a result, the FET 9 is an electronic device that has achieved high speed. As characteristics of the FET 9, R _c (contact resistance) is preferably less than 1 Ωcm, and more preferably less than 0.5 Ωcm. Further, R _s (sheet resistance) is preferably less than 1000 Ωsq, and more preferably less than 500 Ωsq. Further, g _m (mutual conductance) is preferably more than 100 mS, and more preferably more than 1000 mS. Further, fT (cutoff frequency) preferably exceeds 100 GHz, and more preferably exceeds 1 THz.

  Next, with reference to FIG. 1 and FIGS. 7 to 11, a method for manufacturing the FET 9 of the present embodiment will be described. Referring to FIG. 8, in the method of manufacturing FET 9 of the present embodiment, a substrate preparation step is first performed as a step (S110). In this step (S110), the substrate 1 of the first embodiment is prepared (see FIG. 1). The substrate 1 can be manufactured by the manufacturing method described in the first embodiment.

  Next, with reference to FIG. 8, an ohmic electrode formation process is implemented as process (S120). In this step (S120), referring to FIG. 1 and FIG. 9, source electrode 4 and drain electrode 5 are formed in contact with exposed surface 3A of substrate 1. The source electrode 4 and the drain electrode 5 are formed, for example, by forming a mask layer made of a resist having openings corresponding to regions where the source electrode 4 and the drain electrode 5 are to be formed on the exposed surface 3A of the graphene film 3. 4 and the drain electrode 5 can be formed by carrying out lift-off after forming a conductive film made of a conductor (for example, Ni / Au).

  Next, referring to FIG. 8, an insulating film forming step is performed as a step (S130). In this step (S130), referring to FIGS. 9 and 10, the exposed surface 3A of graphene film 3 located between source electrode 4 and drain electrode 5, and the main surface of source electrode 4 on the opposite side of substrate 1 are disposed. An insulating film 61 is formed so as to cover the main surface of the surface and the drain electrode 5 opposite to the substrate 1. The insulating film 61 can be formed by, for example, a CVD method. As a material forming the insulating film 61, for example, silicon nitride can be employed.

  Next, with reference to FIG. 8, a gate electrode formation process is implemented as process (S140). In this step (S140), referring to FIG. 10 and FIG. 11, the gate electrode 7 is in contact with the insulating film 61 covering the exposed surface 3A located between the source electrode 4 and the drain electrode 5. It is formed. For the gate electrode 7, for example, a mask layer made of a resist having an opening corresponding to a region where the gate electrode 7 is to be formed is formed, and a conductive film made of a conductor (for example, Ni / Au) constituting the gate electrode 7 is formed. Then, it can be formed by carrying out lift-off.

  Next, referring to FIG. 8, a contact hole forming step is performed as a step (S150). In this step (S150), referring to FIGS. 11 and 7, contact between source electrode 4 and drain electrode 5 and the wiring is removed by removing insulating film 61 located on source electrode 4 and drain electrode 5. A contact hole is formed to enable this. Specifically, for example, a mask having openings in regions corresponding to the source electrode 4 and the drain electrode 5 is formed, and the insulating film 61 exposed from the openings is removed by etching. As a result, a contact hole is formed, and the remaining insulating film 61 becomes the gate insulating film 6. The gate insulating film 6 covers the exposed surface 3A located between the source electrode 4 and the drain electrode 5, and is the upper surface of the source electrode 4 and the drain electrode 5 (the main surface opposite to the side in contact with the graphene film 3). Extends to the area covering part of the surface.

  Through the above steps, the FET 9 in the present embodiment is completed. Thereafter, for example, wiring is formed and separated into each element by dicing.

  In the present embodiment, the FET 9 in which the source electrode 4, the drain electrode 5, the gate insulating film 6 and the gate electrode 7 are formed on the exposed surface 3A of the substrate 1 of the first embodiment has been described. For example, the source electrode 4, the drain electrode 5, the gate insulating film 6, and the gate electrode 7 may be formed on the exposed surface 3A of the substrate 1 of the second embodiment.

  It should be understood that the embodiments disclosed herein are illustrative in all respects and are not restrictive in any aspect. The scope of the present invention is defined by the scope of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the scope of the claims.

  The substrate of the present application can be applied particularly advantageously to a substrate including a graphene film and an electronic device that require high mobility.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Support substrate 2A 1st main surface 3 Graphene film 3A Exposed surface 4 Source electrode 5 Drain electrode 6 Gate insulating film 7 Gate electrode 9 FET
DESCRIPTION OF SYMBOLS 10 Raw material substrate 11 Substrate 11A 1st main surface 12 SiC film 12A, 12B Main surface 21 Carbon substrate 21A Main surface 22 BN film 22A Main surface 61 Insulating film 90 Heating device 91 Main body part 91A Bottom wall part 91B Side wall part 91C Upper wall part 92 Susceptor 92A Substrate holding surface 93 Cover member 93A Inner wall surface 93C Closed space 95 Gas inlet tube 96 Gas outlet tube 111 Carbon substrate 111A Main surface 112 BN film

Claims (8)

It has a first main surface, and at least a surface layer region including the first main surface is made of any one material selected from the group consisting of boron nitride, molybdenum disulfide, tungsten disulfide, niobium disulfide, and aluminum nitride. A support substrate;
A graphene film disposed on the first main surface and having an atomic arrangement oriented with respect to an atomic arrangement of a material constituting the surface layer region.   The substrate according to claim 1, wherein the graphene film covers 80% or more of the first main surface. The substrate according to claim 1, wherein the graphene film has a carrier mobility of 5000 cm ² / Vs or more.   The substrate according to claim 1, wherein the surface layer region is made of boron nitride. The support substrate is
A base substrate;
A support layer disposed on the base substrate and made of a material different from the base substrate and including the first main surface;
The substrate according to any one of claims 1 to 4, wherein the support layer is the surface layer region.   6. The graphene film according to claim 1, wherein the graphene film has an atomic arrangement in which an area ratio of 20% or more in plan view is oriented with respect to an atomic arrangement of a material constituting the surface layer area. The board | substrate as described in a term. The support substrate has a disc shape,
The board | substrate of any one of Claims 1-6 whose diameter of the said support substrate is 50 mm or more. A substrate according to any one of claims 1 to 7,
A first electrode disposed on an exposed surface that is a main surface opposite to the support substrate side of the graphene film;
An electronic device comprising: a second electrode disposed on the exposed surface and spaced apart from the first electrode.

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