Silicene layer-containing silicon substrate and method for producing same

Abstract

The present invention relates to: a silicene layer-containing silicon substrate having a first carbon doped silicon layer on a silicon substrate, a silicene layer on the first carbon doped silicon layer, and a second carbon doped silicon layer on the silicene layer; and a method for producing the same. Provided is a silicene layer-containing silicon substrate in which a silicene layer is formed on an insulating layer.

Description

Silicon substrate containing a silicene layer and method for producing the same

[0001] The present invention relates to a silicon substrate containing a silicene layer and a method for making the same.

[0002] Two-dimensional materials have been attracting attention in recent years due to their high electron mobility and their potential as sensors. Graphene, which was isolated from graphite in 2004, is a prime example of this.

[0003] Silicon, which is also a group 14 element like carbon, can also adopt the same structure, and while carbon is graphene, the two-dimensional silicon material is known as silicene.

[0004] Silicene was first reported in 2011 and is known to be produced on the surface of silicon films by growing Ag, zirconium diboride, or iridium on the silicon and then heat treating the film at a high temperature (enough to sublimate the silicon).

[0005] Furthermore, germanene is known as a two-dimensional material made of germanium, which is a group 14 element. Patent Document 1 discloses an electronic device using a germanene layer and a method for manufacturing the same.

[0006] Japanese Patent Application Laid-Open No. 2022-124457

[0007] Although silicene is a material that has attracted much attention, just like graphene, it is still in the early stages of research. In particular, if it becomes possible to form silicene on an insulating film, it will be possible to understand the performance of silicene alone.

[0008] However, the most common method for producing silicene is to deposit a metal film such as Ag on a silicon substrate and then heat it at high temperatures to form silicene on the Ag surface, and the only way to form it on an insulating film is by film transfer. However, silicene is very susceptible to oxidation and is difficult to expose to the air like graphene, so film transfer was not possible.

[0009] The present invention has been made to solve the above problems, and an object of the present invention is to provide a silicene layer-containing silicon substrate having a silicene layer formed on an insulating layer, and a method for manufacturing the same.

[0010] The present invention has been made to achieve the above object, and provides a silicene layer-containing silicon substrate having a first carbon-doped silicon layer on a silicon substrate, a silicene layer on the first carbon-doped silicon layer, and a second carbon-doped silicon layer on the silicene layer.

[0011] The silicene layer-containing silicon substrate has a silicene layer formed on an insulating carbon-doped silicon layer, and the second carbon-doped silicon layer can also suppress oxidation of the silicene layer.

[0012] The present invention has also been made to achieve the above-mentioned object, and provides a method for producing a silicene layer-containing silicon substrate, including a first carbon-doped silicon layer formation step of forming a first carbon-doped silicon layer on a silicon substrate, an Ag layer formation step of forming an Ag layer on the first carbon-doped silicon layer, a silicene layer formation step of annealing the silicon substrate to form a silicene layer on the Ag layer, and a second carbon-doped silicon layer formation step of forming a second carbon-doped silicon layer on the silicene layer.

[0013] According to this method for producing a silicene layer-containing silicon substrate, a silicene layer-containing silicon substrate can be obtained in which a silicene layer is formed on an insulating carbon-doped silicon layer. Furthermore, the second carbon-doped silicon layer can suppress oxidation of the silicene layer.

[0014] In this case, in the first carbon-doped silicon layer forming step, epitaxial growth is performed at a growth temperature of 700 to 900° C. using a gas obtained by mixing trimethylsilane, monomethylsilane, or monosilane gas with a carbon source as a raw material, and the carbon concentration is 1×10 ２０ ~4 x 10 ２１ atoms / cm ３ The first carbon-doped silicon layer may be formed by:

[0015] This makes it possible to form a good carbon-doped silicon layer with reduced defects as an insulating layer.

[0016] In this case, in the Ag layer forming step, the Ag layer can be formed to a thickness of 0.3 nm or more by sputtering or vapor deposition.

[0017] This effectively prevents the silicene from forming a non-uniform film structure due to heat treatment being performed in a state where silicon is partially exposed in the silicene layer formation step.

[0018] At this time, in the silicene layer forming step, the annealing can be performed in an atmosphere at a pressure of 133.3 Pa (1 torr) or less and a temperature of 1000° C. or more.

[0019] This allows silicon to sufficiently pass through (sublimate) the Ag film, and the silicene layer can be formed more reliably.

[0020] In this case, in the second carbon-doped silicon layer forming step, epitaxial growth is performed at a growth temperature of 700 to 900° C. using a gas obtained by mixing trimethylsilane, monomethylsilane, or monosilane gas with a carbon source as a raw material, and the carbon concentration is 1×10 ２０ ~4 x 10 ２１ atoms / cm ３ The second carbon-doped silicon layer may be formed by:

[0021] This makes it possible to form a good carbon-doped silicon layer with reduced defects that can effectively prevent the diffusion of oxygen that oxidizes silicene.

[0022] As described above, the silicene layer-containing silicon substrate of the present invention is a silicene layer-containing silicon substrate in which a silicene layer is formed on an insulating carbon-doped silicon layer. Furthermore, the method for producing a silicene layer-containing silicon substrate of the present invention makes it possible to obtain a silicene layer-containing silicon substrate in which a silicene layer is formed on an insulating carbon-doped silicon layer. Furthermore, these silicene layer-containing silicon substrates can also suppress oxidation of the silicene layer due to the second carbon-doped silicon layer.

[0023] 1A and 1B are schematic diagrams illustrating an example of a silicene layer-containing silicon substrate according to an embodiment of the present invention, and a process flow of a method for producing a silicene layer-containing silicon substrate according to an embodiment of the present invention.

[0024] The present invention will be described in detail below, but the present invention is not limited thereto.

[0025] As described above, there has been a need for a silicene layer-containing silicon substrate in which a silicene layer is formed on an insulating layer, and a method for manufacturing the same.

[0026] As a result of extensive research into the above-mentioned problems, the present inventors have discovered that a silicene layer-containing silicon substrate having a first carbon-doped silicon layer on a silicon substrate, a silicene layer on the first carbon-doped silicon layer, and a second carbon-doped silicon layer on the silicene layer results in a silicene layer-containing silicon substrate in which a silicene layer is formed on an insulating carbon-doped silicon layer, and have completed the present invention.

[0027] The present inventors have also conducted extensive research into the above-mentioned problems and have found that a silicene layer-containing silicon substrate in which a silicene layer is formed on an insulating carbon-doped silicon layer can be obtained by a method for producing a silicene layer-containing silicon substrate, the method including: a first carbon-doped silicon layer formation step of forming a first carbon-doped silicon layer on a silicon substrate; an Ag layer formation step of forming an Ag layer on the first carbon-doped silicon layer; a silicene layer formation step of annealing the silicon substrate to form a silicene layer on the Ag layer; and a second carbon-doped silicon layer formation step of forming a second carbon-doped silicon layer on the silicene layer, thereby completing the present invention.

[0028] [Silicen Layer-Containing Silicon Substrate] A silicene layer-containing silicon substrate according to the present invention will now be described with reference to Fig. 1. Fig. 1 is a schematic diagram of an example of a silicene layer-containing silicon substrate according to an embodiment of the present invention.

[0029] As shown in FIG. 1 , a silicene layer-containing silicon substrate 1 according to the present invention is a silicene layer-containing silicon substrate having a first carbon-doped silicon layer 3 on a silicon substrate 2, a silicene layer 5 on the first carbon-doped silicon layer 3, and a second carbon-doped silicon layer 6 on the silicene layer 5.

[0030] The silicene layer-containing silicon substrate 1 may comprise an Ag layer 4 between the first carbon-doped silicon layer 3 and the silicene layer 5 .

[0031] The silicon substrate 2 is not particularly limited, but may be a silicon single crystal substrate having a diameter of 100 mm or more, which may be manufactured using conventional single crystal manufacturing equipment and procedures.

[0032] The carbon concentration of the first carbon-doped silicon layer 3 is 1×10 ２０ ~4 x 10 ２１ atoms / cm ３ The range is preferably 4×10 ２０ ~8 x 10 ２０ atoms / cm ３ This makes it possible to obtain a good carbon-doped silicon layer as an insulating layer with reduced defects.

[0033] The carbon concentration of the second carbon-doped silicon layer 6 is 1×10 ２０ ~4 x 10 ２１ atoms / cm ３ The range is preferably 4×10 ２０ ~8 x 10 ２０ atoms / cm ３ This results in a good carbon-doped silicon layer in which defects are suppressed and which can effectively prevent the diffusion of oxygen that oxidizes silicene.

[0034] Such a silicene layer-containing silicon substrate 1 is a silicene layer-containing silicon substrate in which the silicene layer 5 is formed on the insulating first carbon-doped silicon layer 3. Furthermore, the second carbon-doped silicon layer 6 can also suppress oxidation of the silicene layer 5.

[0035] [Method for Producing a Silicene Layer-Containing Silicon Substrate] Next, a method for producing a silicene layer-containing silicon substrate according to the present invention will be described. Figure 2 is a schematic diagram showing an example of a process flow for producing a silicene layer-containing silicon substrate according to an embodiment of the present invention. As shown in Figure 2, the method for producing a silicene layer-containing silicon substrate 1 according to the present invention includes a first carbon-doped silicon layer formation step (S1) of forming a first carbon-doped silicon layer 3 on a silicon substrate 2, an Ag layer formation step (S2) of forming an Ag layer 4 on the first carbon-doped silicon layer 3, a silicene layer formation step (S3) of annealing the silicon substrate to form a silicene layer 5 on the Ag layer 4, and a second carbon-doped silicon layer formation step (S4) of forming a second carbon-doped silicon layer 6 on the silicene layer 5.

[0036] (First carbon-doped silicon layer forming step: S1) First, a first carbon-doped silicon layer 3 is formed on a silicon substrate 2. The first carbon-doped silicon layer 3 can be formed on the silicon substrate 2 by epitaxial growth under reduced pressure in a reduced-pressure CVD apparatus using, as a raw material, a gas obtained by mixing a carbon source with, for example, trimethylsilane, monomethylsilane, or monosilane gas.

[0037] The growth temperature is preferably 700 to 900° C., and more preferably 730 to 750° C. This makes it possible to form an epitaxial layer with fewer defects.

[0038] The carbon concentration is 1 x 10 ２０ ~4 x 10 ２１ atoms / cm ３ The range is preferably 4×10 ２０ ~8 x 10 ２０ atoms / cm ３ It is more preferable that the range is 1. This makes it possible to form a good carbon-doped silicon layer with reduced defects as the insulating layer.

[0039] The growth temperature and carbon concentration can be adjusted in consideration of the thickness of the Ag layer 4 and the silicene layer 5 to be subsequently deposited.

[0040] The thickness of the first carbon-doped silicon layer 3 is not particularly limited, and can be adjusted in consideration of the thicknesses of the Ag layer 4 and the silicene layer 5 to be subsequently stacked, but a thickness of 50 nm is sufficient as a guideline.

[0041] (Ag Layer Forming Step: S2) Next, a thin film of Ag is formed on the first carbon-doped silicon layer 3, that is, the Ag layer 4 is formed. The Ag layer 4 can be formed by, for example, sputtering or vapor deposition.

[0042] In this case, the thickness of the Ag layer 4 can be set to 0.3 nm or more, i.e., a thickness of a monoatomic layer or more. If the thickness is 0.3 nm or more, a uniform silicene layer 5 can be formed over the entire surface of the silicon substrate 2 in the silicene layer formation step (S3).

[0043] Although the upper limit of the thickness of the Ag layer 4 is not particularly limited, it can be set to 5 nm. If the thickness is 5 nm or less, silicon can be efficiently diffused in the silicene layer formation step (S3), and the silicene layer 5 can be formed more reliably.

[0044] (Silicenes Layer Forming Step: S3) Next, the silicon substrate is annealed to form a silicene layer 5 on the Ag layer 4. By annealing, Si is sublimated, and the silicene layer 5 is formed on the Ag layer 4.

[0045] Annealing can be performed in a low pressure CVD apparatus, which allows sequential epitaxial processing within the same apparatus.

[0046] At this time, the annealing can be performed in an atmosphere at a pressure of 133.3 Pa (1 torr) or less and a temperature of 1000° C. or more.

[0047] If the pressure is 1 torr or less, silicon can sufficiently pass through (sublimate) the Ag film, and the silicene layer 5 can be more reliably formed. The lower limit is not particularly limited, but can be set to 0.1 torr. If the pressure is 0.1 torr or more, restrictions on the device caused by high vacuum, such as the ultimate vacuum capacity, can be effectively avoided.

[0048] The upper limit of the temperature is not particularly limited, but is preferably 1400° C. or less (the melting point of silicon or less). Taking into consideration wafer deformation and the heating mechanism of the apparatus, 1200° C. or less is more preferable.

[0049] (Second carbon-doped silicon layer formation step: S4) Like silicene, germanene is also susceptible to oxidation, and Patent Document 1 describes a method for preventing oxidation of a germanene layer by using a cap layer. As this cap layer, a cap layer for preventing oxidation of silicene is also formed in the present invention.

[0050] Specifically, a second carbon-doped silicon layer 6 is formed on the silicene layer 5. The second carbon-doped silicon layer 6 can be formed by epitaxially growing the silicon layer 6 on a silicon substrate under reduced pressure in a low-pressure CVD apparatus using, as a raw material, a gas obtained by mixing a carbon source with, for example, trimethylsilane, monomethylsilane, or monosilane gas.

[0051] The growth temperature is preferably 700 to 900° C., and more preferably 730 to 750° C. This makes it possible to form an epitaxial layer with fewer defects.

[0052] The carbon concentration is 1 x 10 ２０ ~4 x 10 ２１ atoms / cm ３ The range is preferably 4×10 ２０ ~8 x 10 ２０ atoms / cm ３ This makes it possible to form a good carbon-doped silicon layer in which defects are suppressed and which can effectively prevent the diffusion of oxygen that oxidizes silicene.

[0053] The growth temperature and carbon concentration can be adjusted in consideration of the thickness of the first carbon-doped silicon layer and the silicene layer to be deposited.

[0054] Furthermore, there are no particular limitations on the thickness of the second carbon-doped silicon layer 6, and a thickness of 50 nm is sufficient as a guideline. In this manner, a silicon substrate sandwiching a silicene layer can be fabricated.

[0055] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0056] First, a single crystal silicon substrate with a diameter of 100 mm, a plane orientation (100), boron doping, and a resistivity of 10 Ω cm was prepared. Then, carbon was doped onto the silicon substrate at 700°C and 10 torr using trimethylsilane as a source gas. ２０ atoms / cm ３ A doped Si layer (first carbon-doped silicon layer) was grown to a thickness of 50 nm.

[0057] Thereafter, a 1 nm thick Ag film was formed on the first carbon-doped silicon layer by sputtering.

[0058] Next, this wafer was loaded into a reduced pressure CVD apparatus and annealed at 1170° C. for 70 minutes in a hydrogen atmosphere under a reduced pressure of 0.1 torr to form a silicene layer on the Ag layer.

[0059] Furthermore, using trimethylsilane as the source gas, carbon was added at 1×10 ２０ atoms / cm ３ A doped Si layer (second carbon-doped silicon layer) was grown to a thickness of 50 nm to prepare a substrate with a silicene intermediate layer.

[0060] As a result, a silicon substrate containing a silicene layer was obtained, in which a silicene layer was formed on an insulating carbon-doped silicon layer.

[0061] This specification includes the following aspects: [1]: A silicene layer-containing silicon substrate having a first carbon-doped silicon layer on a silicon substrate, a silicene layer on the first carbon-doped silicon layer, and a second carbon-doped silicon layer on the silicene layer. [2]: A method for producing a silicene layer-containing silicon substrate, including a first carbon-doped silicon layer formation step of forming a first carbon-doped silicon layer on a silicon substrate, an Ag layer formation step of forming an Ag layer on the first carbon-doped silicon layer, a silicene layer formation step of annealing the silicon substrate to form a silicene layer on the Ag layer, and a second carbon-doped silicon layer formation step of forming a second carbon-doped silicon layer on the silicene layer. [3]: In the first carbon-doped silicon layer formation step, epitaxial growth is performed at a growth temperature of 700 to 900°C using a gas obtained by mixing trimethylsilane, monomethylsilane, or monosilane gas with a carbon source as a raw material, to form a silicene layer having a carbon concentration of 1×10 ２０ ~4 x 10 ２１ atoms / cm ３ [4]: A method for producing a silicene layer-containing silicon substrate according to [2] above, which comprises forming the first carbon-doped silicon layer by sputtering or vapor deposition in the Ag layer formation step. [5]: A method for producing a silicene layer-containing silicon substrate according to [2] above, [3] above, or [4] above, which comprises performing the annealing in the silicene layer formation step under a pressure of 133.3 Pa (1 torr) or less and an atmosphere of 1000°C or higher. [6]: A method for producing a silicene layer-containing silicon substrate according to [2] above, [3] above, or [4] above, which comprises performing epitaxial growth at a growth temperature of 700 to 900°C using a gas obtained by mixing a carbon source with trimethylsilane, monomethylsilane, or monosilane gas as a raw material in the second carbon-doped silicon layer formation step, which comprises forming the Ag layer by sputtering or vapor deposition in the Ag layer formation step. ２０ ~4 x 10 ２１ atoms / cm ３ The method for producing a silicene layer-containing silicon substrate according to [2], [3], [4] or [5], comprising forming the second carbon-doped silicon layer.

[0062] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A silicene layer-containing silicon substrate comprising a first carbon-doped silicon layer on a silicon substrate, a silicene layer on the first carbon-doped silicon layer, and a second carbon-doped silicon layer on the silicene layer.

2. A method for producing a silicene layer-containing silicon substrate, comprising: a first carbon-doped silicon layer formation step of forming a first carbon-doped silicon layer on a silicon substrate; an Ag layer formation step of forming an Ag layer on the first carbon-doped silicon layer; a silicene layer formation step of annealing the silicon substrate to form a silicene layer on the Ag layer; and a second carbon-doped silicon layer formation step of forming a second carbon-doped silicon layer on the silicene layer.

3. In the first carbon-doped silicon layer forming step, epitaxial growth is performed at a growth temperature of 700 to 900°C using a gas obtained by mixing trimethylsilane, monomethylsilane, or monosilane gas with a carbon source as a raw material, and the carbon concentration is 1 x 10 ２０ ~4 x 10 ２１ atoms / cm ３ 3. The method for manufacturing a silicon substrate containing a silicene layer according to claim 2, further comprising forming the first carbon-doped silicon layer.

4. The method for producing a silicon substrate containing a silicene layer according to claim 2, characterized in that in the Ag layer formation step, the Ag layer is formed to a thickness of 0.3 nm or more by sputtering or vapor deposition.

5. The method for producing a silicon substrate containing a silicene layer according to claim 2, wherein in the silicene layer forming step, the annealing is carried out in an atmosphere at a pressure of 133.3 Pa (1 Torr) or less and a temperature of 1000° C. or more.

6. In the second carbon-doped silicon layer forming step, epitaxial growth is performed at a growth temperature of 700 to 900°C using a gas obtained by mixing trimethylsilane, monomethylsilane, or monosilane gas with a carbon source as a raw material, and a carbon concentration of 1 x 10 ２０ ~4 x 10 ２１ atoms / cm ３ The method for producing a silicon substrate containing a silicene layer according to any one of claims 2 to 5, further comprising forming the second carbon-doped silicon layer.

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