JP2006213578A - Diamond single crystal substrate and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diamond single crystal substrate having a diamond single crystal film capable of being practically used as a semiconductor; and a method for manufacturing the same by which the diamond single crystal substrate can be easily obtained. <P>SOLUTION: The diamond single crystal substrate, in which an SrO single crystal layer 2, an Sr layer or a Ti layer 3, and a diamond single crystal layer 4 are sequentially stacked on an Si single crystal substrate 1, is obtained by epitaxially growing the SrO single crystal layer 2 having a thickness of 1-100 nm, then forming the Sr or the Ti layer 3 having a thickness of 1-2 atoms, and epitaxially growing the diamond single crystal layer 4 on the layer 3 by using an activated hydrocarbon raw material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a diamond single crystal substrate that can be used as a semiconductor and a method for manufacturing the same.

In addition to its value as a gemstone, diamond is used in industrial applications such as cutting stones and polishing semiconductor materials because it is the hardest material.
Furthermore, it has excellent properties such as high thermal conductivity, wide light transmission wavelength band, low dielectric constant, chemical stability, etc., so it can be widely applied to semiconductor devices, electron emission devices, biosensors, light emitting elements, etc. Is expected. In particular, application as a semiconductor is expected, and for that purpose, a single crystal that can make use of the excellent characteristics of diamond as described above is required.

In the conventional high-temperature and high-pressure synthesis method, although there is a technique for producing a crystal of several millimeters or less, it is difficult to synthesize diamond having a practical size exceeding 10 mm necessary for diamond device development.
Therefore, in recent years, various studies have been conducted with the aim of increasing the size of a diamond single crystal by a gas phase synthesis method of synthesizing diamond from a gas.

  In the above-mentioned vapor phase synthesis method, diamond is vapor-grown on a substrate, but heteroepitaxial growth using various substrates has been tried in addition to the method of homoepitaxial growth on a natural or synthetic diamond substrate. It has been.

However, in the Si substrate and the 3C-SiC substrate, although a mosaic crystal is obtained, a single crystal film is not obtained.
Although heteroepitaxial growth on c-BN has also been reported, it has a problem that it is difficult to obtain c-BN itself as a large crystal.
There is also a report of heteroepitaxial growth on iridium (Ir). Ir does not react with carbon below 1000 ° C., and the lattice constant is said to be relatively good, but it is still about 7%.

  As described above, in order to synthesize a diamond single crystal by heteroepitaxial growth, a substrate that does not increase the internal stress of the thin film due to interstitial mismatch is preferable, and selection of the substrate based on this viewpoint is very important. .

By the way, in Patent Document 1, when a strontium (Sr) thin film is grown on a semiconductor substrate such as Si, an interface structure not including a transition layer such as SiO ₂ or SrSi ₂ is formed by forming a SrO thin film. It is disclosed that the internal stress of the thin film can be relaxed without any problem.
JP 2003-209106 A

  As described above, a diamond single crystal can be produced by a high-pressure synthesis method or a gas phase synthesis method, but a low-resistance n-type semiconductor has not yet been produced, and a large single crystal can be obtained. This is a major limitation in the development of semiconductors using diamond.

  Therefore, the present inventors have conducted research to make a diamond single crystal having excellent characteristics as described above usable as a semiconductor, and as a result, oxides disclosed in Patent Document 1 above. It has been found that a large single crystal film of diamond can be formed by utilizing the formation of a thin film.

  An object of the present invention is to provide a diamond single crystal substrate provided with a diamond single crystal film that can be practically used as a semiconductor, and a manufacturing method capable of easily obtaining the same.

The diamond single crystal substrate according to the present invention includes a strontium oxide (SrO) single crystal layer, a strontium (Sr) layer having a thickness of 1 to 2 atoms or a titanium (Ti) layer, and a diamond single crystal layer on a Si single crystal substrate. It is characterized by being sequentially laminated.
With the above configuration, a diamond / SrO / Si (001) heterojunction is well formed, and a diamond single crystal substrate that can be used as a semiconductor can be obtained.

In addition, the method for producing a diamond single crystal substrate according to the present invention includes an epitaxial growth of a SrO single crystal layer having a thickness of 1 nm to 100 nm on a Si single crystal substrate, and then a Sr or Ti layer having a thickness of 1 to 2 atoms. And a diamond single crystal layer is epitaxially grown on the activated hydrocarbon raw material.
As described above, after a SrO single crystal layer is formed on a Si substrate, a diamond single crystal is epitaxially grown to form a heterojunction capable of integrating a plurality of elements, which is practical as a semiconductor. A simple diamond single crystal substrate can be obtained.

As described above, according to the method for manufacturing a diamond single crystal substrate according to the present invention, a practical diamond semiconductor substrate can be obtained more easily than conventional high-pressure synthesis methods and gas phase synthesis methods.
In addition, the diamond single crystal substrate of the present invention obtained by the above manufacturing method is applied to device materials in the fields of energy, information communication, environment-resistant electronics, etc. due to the excellent characteristics of diamond itself and its characteristics as a semiconductor. In addition, an electron emission material utilizing the property of negative electron affinity, a SAW (surface acoustic wave) filter utilizing a large elastic modulus, and application to a biochip based on a biological constituent element are also expected.

Hereinafter, the present invention will be described in more detail.
In FIG. 1, the outline of the process of the manufacturing method of the diamond single crystal substrate based on this invention is shown.
The manufacturing method according to the present invention includes a step of epitaxially growing a SrO single crystal layer 2 having a thickness of 1 nm to 100 nm on a Si single crystal substrate 1 (FIG. 1A) (FIG. 1B), and further thereon. Next, a step of forming a Sr or Ti layer 3 having a thickness of 1 to 2 atoms (FIG. 1 (c)), and a step of epitaxially growing a diamond single crystal layer 4 thereon using an activated hydrocarbon raw material (FIG. 1). (D)).
That is, the method for manufacturing a diamond single crystal substrate according to the present invention is to epitaxially grow a diamond single crystal based on the epitaxial growth of SrO on Si.
Thereby, a heterojunction of diamond / SrO / Si (001) can be satisfactorily formed, and a semiconductor substrate capable of integrating a plurality of elements can be obtained.

  According to such a manufacturing method according to the present invention, a diamond single crystal substrate according to the present invention in which an SrO single crystal layer, an Sr layer or a titanium Ti layer, and a diamond single crystal layer are sequentially laminated on an Si single crystal substrate. The diamond single crystal substrate can be widely used as a practical semiconductor.

In the manufacturing method according to the present invention, first, the SrO single crystal layer 2 is epitaxially grown on the Si single crystal substrate 1 (see FIG. 1B).
SrO is an ionic crystal having a rock salt structure with a lattice constant of about 0.515 nm. When the SrO (001) plane is rotated by 45 °, the surface has a face-centered cubic structure, and the length of the side is 0.382 nm, which is very close to 0.364 nm, which is the lattice constant of diamond ( (Lattice mismatch: about 5%).
For this reason, it is considered that diamond can be epitaxially grown in the <001> direction on SrO (001) while being rotated in the plane of 45 °.

The Si single crystal substrate 1 in the present invention is not limited to those manufactured by the CZ (Czochralski) method, but those manufactured by the FZ (floating zone) method, and these Si single crystal substrates are vapor-phased. An epitaxially grown Si single crystal layer (Si epi substrate) or the like may be used, but a crystal plane orientation (001) is preferably used.
The Si single crystal can be easily manufactured as a large bulk, and since the wafer processing technology is mature, it can be suitably used as a substrate for element formation.
Note that the epitaxial growth has an advantage that a single crystal layer (epi layer) having excellent crystallinity can be obtained and the crystal plane orientation of the substrate can be inherited by the epi layer.
Further, in the present invention, before the SrO single crystal layer 2 is formed, the natural oxide film on the surface of the Si substrate 1 need not be removed.

The SrO single crystal layer 2 is formed by forming a film with an RF sputtering apparatus at a substrate temperature of 700 to 900 ° C. using a sintered SrO target as a raw material and a mixed gas of Ar and O ₂ as a sputtering gas. (See FIG. 1 (b)).
The thickness of the SrO single crystal layer 2 is preferably 1 nm or more and 100 nm or less in order to satisfactorily form a diamond / SrO / Si (001) heterojunction.

Next, a Sr or Ti layer 3 having a thickness of 1 to 2 atoms is formed on the SrO single crystal layer 2 (see FIG. 1C).
Specifically, the substrate temperature is lowered to room temperature, and a Sr or Ti layer 3 having a thickness of 1 to 2 atoms is formed by sputtering using a Sr or Ti metal target as a raw material and Ar as a sputtering gas. Can do.
Since SrO (001) formed as described above also exposes oxygen on the surface, there is a possibility that the adhesion of carbon (C) may be inhibited. Therefore, a Sr or Ti layer of 1 to 2 atomic layers is provided on the surface Thus, adsorption of C can be promoted.

Then, the diamond single crystal layer 4 is epitaxially grown on the Sr or Ti layer 3 by using an activated hydrocarbon raw material (see FIG. 1D).
In the epitaxial growth, a high-quality diamond single crystal thin film can be deposited by activating a reactive gas containing carbon using microwave plasma, RF plasma, hot filament, or the like.
As the reactive gas used in this CVD method, hydrocarbons such as CH ₄ and C ₃ H _8, substances containing oxygen such as CH ₃ OH containing oxygen, C ₂ H ₅ OH, CO and CO ₂ are used. This is diluted with hydrogen gas and then activated by microwave plasma or the like to precipitate a diamond single crystal.
Specifically, for example, in a microwave plasma CVD apparatus, activated methane is supplied at a rate of about 1 Torr in a hydrogen stream at 1 scm in terms of 100%, and the diamond single crystal layer 4 is thickened at 700 to 1000 ° C. Epitaxial growth is preferably performed until the thickness becomes 1 μm or more.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not restrict | limited by the following Example.
First, an SrO single crystal layer having a thickness of 100 nm at 800 ° C. using a sintered SrO target as a raw material and Ar and O ₂ as sputtering gases on a natural oxide film of a Si (001) single crystal substrate using an RF sputtering apparatus. Formed.
Next, the temperature was lowered to room temperature, and an Sr layer having a thickness of 1 to 2 atoms was formed by sputtering using an Sr target as a raw material and Ar as a sputtering gas.
Further, methane activated by microwave plasma is supplied at 1 scm in 100% conversion, and a diamond single crystal layer is epitaxially grown at 800 ° C. until the thickness becomes 1 μm or more, thereby obtaining a desired diamond single crystal semiconductor film. Formed.

It is sectional drawing which shows the outline of the process of the manufacturing method of the diamond single crystal substrate which concerns on this invention.

Explanation of symbols

1 Si single crystal substrate 2 SrO single crystal layer 3 Sr or Ti layer 4 Diamond single crystal layer

Claims (2)

  A diamond single crystal substrate, wherein a strontium oxide single crystal layer, a strontium layer having a thickness of 1 to 2 atoms or a titanium layer, and a diamond single crystal layer are sequentially laminated on a Si single crystal substrate.   After epitaxially growing a strontium oxide single crystal layer having a thickness of 1 nm or more and 100 nm or less on a Si single crystal substrate, a strontium or titanium layer having a thickness of 1 to 2 atoms is formed, and an activated hydrocarbon raw material is formed thereon. A method for producing a diamond single crystal substrate, comprising epitaxially growing a diamond single crystal layer by:

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