JP2615406B2 - Method for manufacturing silicon substrate having silicon carbide buried layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for manufacturing a silicon substrate having a silicon carbide buried layer.

[0002]

2. Description of the Related Art Silicon carbide has a large energy band gap of 2.4 eV at 3 C and 3.0 eV at 6 H, and has high thermal conductivity. It is used as such.
In this case, if a silicon carbide layer as thick as possible can be formed in the silicon substrate, the utility value in various fields can be further enhanced.

[0003] As a method of forming a single crystal bulk of silicon carbide, there are a sublimation method, a liquid phase method, and the like. A silicon carbide substrate is manufactured by slicing and polishing the single crystal bulk formed by these methods.

However, it is difficult to synthesize a large single crystal by the above-described single crystal bulk silicon carbide synthesis method. In addition, silicon carbide has many crystal polymorphs, and the properties thereof vary greatly depending on the shape. Therefore, it is necessary to make the crystal form suitable for the purpose, but it is extremely difficult to control the above-mentioned synthesis method.

[0005] On the other hand, as a method of forming a silicon carbide thin film, methods such as chemical vapor deposition, sputter vapor deposition, and ion implantation are known. There is an example in which carbon ions are implanted to form a silicon carbide thin film on a silicon substrate.

However, in the above conventional ion implantation method,
For reasons such as low energy, the silicon carbide layer is limited to a very surface portion (about 0 to 0.5 μm) and cannot be ion-implanted in large quantities. Moreover, when the implantation region is increased, silicon carbide can be formed over a large area, but amorphous silicon carbide is formed, and cannot be single-crystallized by heat treatment, so that it remains in a polycrystalline state.

[0007]

SUMMARY OF THE INVENTION The main object of the present invention is to form a single-crystal silicon carbide layer having the same crystal orientation as single-crystal silicon as thick as possible at a certain depth from the surface of a silicon substrate. .

[0008]

Means for Solving the Problems The present inventor has made extensive studies in view of the above-mentioned problems of the prior art. As a result, in the ion implantation method, carbon ions having a constant energy were converted to silicon ions kept at a specific temperature. When injecting into the substrate,
The present inventors have found that a silicon carbide layer in a single crystal state can be formed as an intermediate layer at a certain depth from the surface while holding the single crystal silicon layer on the surface, and have completed the present invention.

That is, the present invention provides a method for manufacturing a silicon substrate having the following silicon carbide buried layer. 1. In a method of forming a silicon carbide layer by implanting carbon ions into a silicon substrate, 800 to 1300
200k for single crystal silicon substrate heated and held at ℃
A method for manufacturing a silicon substrate having a silicon carbide buried layer, wherein carbon ions having energy of eV or more are implanted.

Hereinafter, the present invention will be described in detail.

The silicon substrate manufactured by the method of the present invention has a single-crystal silicon layer on the surface thereof, and a single-crystal silicon carbide layer having the same crystal orientation as the substrate under the single-crystal silicon layer.

The manufacturing method will be described below. First, as a silicon substrate that can be used in the present invention, a substrate manufactured by a known manufacturing method can be used.

Next, the silicon substrate is coated with 800 to 13
Heat and hold at 00 ° C. If the temperature is higher than 1300 ° C., the polymorph 6H may not be obtained, which is not preferable. It is desirable that heating and holding be performed in a vacuum. Next, a silicon carbide layer is formed by implanting carbon ions into the heated silicon substrate. Carbon ions are accelerated by giving energy of 200 keV or more. Since carbon ions in a high energy state are used, etching of the silicon substrate surface by sputtering can be avoided. As a result, a large amount of carbon ions up to the same concentration as the substrate silicon can be implanted. in this case,
The upper limit of the energy to be accelerated may be appropriately adjusted depending on the desired depth and thickness of the silicon carbide buried layer, but is usually about 1 GeV. As a device for accelerating carbon ions, a known accelerator can be used, and examples thereof include a tandem accelerator, a high-frequency quadrupole accelerator, and a cyclotron. Other operation methods and conditions in the ion implantation may be in accordance with a normal ion implantation method.

By implanting carbon ions into the high-temperature substrate in this manner, the surface layer has a single crystal structure having the same crystal orientation as the silicon substrate while maintaining the original silicon single crystal state. The layer can be formed to a certain depth.

[0015]

According to the manufacturing method of the present invention, the silicon substrate surface is not etched by sputtering, that is, the surface layer has the same crystal orientation as the silicon single crystal while maintaining the original silicon single crystal state. A silicon substrate having a silicon carbide buried layer made of a single crystal as an intermediate layer can be obtained. Moreover, the depth and thickness of the silicon carbide buried layer can be freely controlled by adjusting the energy applied to the carbon ions.

Accordingly, the silicon substrate according to the present invention having such a unique structure is particularly useful for various electronic materials. For example, when an electronic device having a SiC-Si heterojunction is manufactured, a conventional semiconductor process can be applied as it is because the surface is a silicon single crystal layer. When an oxide film (SiO ₂ ) is formed on a silicon carbide layer, silicon carbide is conventionally directly oxidized by a thermal oxidation method. On the other hand, in a substrate obtained by the method of the present invention, a surface layer is formed. Need only be oxidized as it is, and an oxide film can be formed at a lower temperature and at a higher speed.

[0017]

EXAMPLES Examples and comparative examples are shown below to further clarify the features of the present invention.

EXAMPLE 1 Carbon ions having an energy of 1.5 MeV were implanted into a silicon single crystal substrate kept at 880 ° C. in a vacuum at 1.5 × 10 ¹⁸ cm ⁻² using a tandem accelerator. The substrate of the present invention was obtained.

FIG. 1 shows the result of measuring the concentration distribution of carbon in the depth direction in the substrate obtained in this manner by using the Rutherford backscattering method. As is clear from FIG. 1, carbon does not exist on the substrate surface, but forms a silicon carbide layer at a certain depth from the surface.

FIGS. 2 and 3 show the results of analyzing the silicon carbide by X-ray diffraction analysis. From this result,
Only cubic silicon carbide (3C type) is formed,
Moreover, the silicon substrate (400) surface and the silicon carbide (200)
Since the directions in which plane diffraction occurs coincide, it can be seen that the crystal orientations are the same.

[Brief description of the drawings]

FIG. 1 is a diagram showing a carbon concentration distribution by a Rutherford backscattering method showing a state of a buried silicon carbide layer in a silicon substrate obtained by a method of the present invention.

FIG. 2 is a positive pole figure of X-ray diffraction from a silicon (400) plane in a silicon substrate obtained by the method of the present invention.

FIG. 3 is a positive pole figure of X-ray diffraction from a silicon carbide (200) plane in a silicon substrate obtained by the method of the present invention.

Claims (1)

(57) [Claims] In a method for forming a silicon carbide layer by implanting carbon ions into a silicon substrate, the method comprises the steps of:
A method for manufacturing a silicon substrate having a silicon carbide buried layer, characterized by implanting carbon ions having an energy of 200 keV or more into a single crystal silicon substrate heated and held at 1300 ° C.