JPS62155512A - Epitaxial growth of beta-si - Google Patents

Abstract

PURPOSE:To enable growth of beta-Si at a low temperature of 1,000 deg.C without using a buffer layer by employing the mixing gas of trichlor-silane, lower hydrocarbon and hydrogen and growing beta-SiC in the vapor phase on an silicon 111 substrate displaced in the specific direction under the specific conditions of decompression. CONSTITUTION:A reaction furnace such as an induction heating type reaction furnace is used as a growth device, an exhaust system is connected to the reaction furnace, and the mixing gas of trichlor-silane (SiHCl3), propane (C3H8) and hydrogen (H2) is introduced from a gas introducing port. Pressure in the furnace is controlled under the specific condition of decompression of 1,000Pa or less such as 200Pa. A substrate having a 111 crystal face and displaced at 1-6 deg. in the specific direction <2-1-1> direction is employed as an silicon- wafer used. When the silicon substrate is heated at approximately 1,000 deg.C and grown in the vapor phase by said device, beta-SiC can be grown at speed of approximately 250-450Angstrom /min. Lower hydrocarbon gas, such as methane (CH4), acetylene (C2H2), etc. can be employed besides said substance as hydrocarbon.

Description

[Detailed Description of the Invention] [Summary] Silicon carbide (SiC) is a material with excellent heat resistance properties, radiation resistance properties, etc. However, although it is an essential condition for semiconductor materials to be able to epitaxially grow on a substrate, development has not progressed sufficiently. The present invention describes a method that enables the growth of β-SiC crystals on a silicon substrate at a lower temperature than conventional methods.

[Industrial application field]

The present invention relates to a method of growing β-5iC on a silicon substrate.

Currently, silicon occupies the mainstream as a semiconductor material, but silicon is one of the semiconductor materials that complements the characteristics of silicon.
There is C.

SiC has cubic, hexagonal, and orthorhombic crystal structures. Among these, the most common ones are 3C-SiC (β-SiC), which has a repeating cycle of three layers, and 6H-SiC (α-SiC), which has a repeating cycle of six layers.

The temperature at which silicon retains its characteristics as a semiconductor is 300°C or lower, while that of SiC is 500 to 600°C.

The energy gap value is 1.1 eV for silicon, 2.2 to 2.4 eV for β-SiC, and 3 for α-SiC.
, OeV.

However, in order to utilize this, it is necessary to obtain a large SiC substrate, which requires the development of a technology that enables epitaxial growth on the substrate.

Although the technical development of epitaxial growth of β-SiC is gradually progressing, many problems still remain.

[Conventional technology]

There are methods for growing SiC, such as sublimation, sputtering, ion implantation, molecular beam epitaxial method, and melting, but it is not easy to grow over a large area.

Another method is the CVD method. β-S by CVD method below
Epitaxial growth of iC will be explained.

When growing SiC on a silicon substrate, the lattice constant of silicon is 5.430 N, while the lattice constant of SiC is 4.358 N, which is about a 20% difference. Therefore, it is not possible to directly grow SiC crystals on a silicon substrate.

Therefore, during epitaxial growth, a thin buffer layer is usually formed on the surface of the silicon substrate. For example, propane gas (C3
H8) is added and heated to 1300 to 1400°C to form a thin carbonized layer on the surface of the silicon.

After that, the temperature was lowered several tens of degrees and monosilane (Si
H4) is added to perform β-SiC crystal growth.

With the above growth method, approximately 200 to 400 β-
The growth rate of SiC can be obtained.

[Problem that the invention seeks to solve]

In the conventional CVD method described above, the growth temperature is extremely high.

In all semiconductor processes, it is desirable to keep substrate temperatures as low as possible.

Furthermore, if epitaxial growth could be performed directly on a silicon substrate, the process would be simplified and convenient.

Furthermore, it is practically necessary to grow it with a good yield on a silicon wafer of about 4 or 5 inches.

There remains the problem of removing high-density crystal defects and surface defects in the film quality of β-SiC.

[Means for solving problems]

The above problem can be solved by using a mixed gas of trichlorosilane, lower hydrocarbons, and hydrogen under reduced pressure conditions of 1000 Pa or less.
11) Solved by the growth method of the present invention, which consists of vapor phase growth of β-Si C on a substrate.

As the lower hydrocarbon, any of methane, propane, and acetylene gases can be used, and propane and acetylene gases can be used.
When using gas, the growth temperature is about 1000°C, and by using acetylene gas, it is possible to lower the temperature further by about 100°C.

[Effect]

Epitaxial growth largely depends on the plane orientation of the substrate on which crystal growth is to be performed.

Normally, a (100) substrate is used in silicon semiconductor devices, but as a result of experiments, the present invention uses a (111) substrate shifted by 1 to 6 degrees in the <211> direction, and uses trichlorosilane 5iHC11 as the Si source gas. Therefore, it is not necessary to form a buffer layer, which is 1000℃.
It was found that it can be obtained at low temperatures.

This is because conventional monosilane gas thermally decomposes and forms crystal nuclei in the gas phase, whereas trichlorosilane gas does not react in the gas phase and the reaction progresses only on the substrate surface. This is thought to be due to this.

〔Example〕

An embodiment according to the present invention will be described in further detail. An induction heating reactor is used as the growth apparatus, and a silicon wafer is mounted on a graphite susceptor coated with SiC.

An exhaust system is connected to the reactor, and trichlorosilane (SiHCb) and propane (C3H8
), a mixed gas of hydrogen (H2) is introduced. The pressure in the furnace is controlled at 200 Pa.

The silicon wafer used is a substrate with a (111) crystal plane and a deviation of 1 to 6 inches in the <211> direction.Results using a normal (100) silicon positive substrate are also included for comparison. The relationship between these crystal planes is schematically shown in FIG.

When a silicon substrate is heated to about 1000°C and vapor phase grown using the above equipment, β-SiC can be grown at 250 to 450 people/min.
can grow at a rate of

As a typical example, the above β-SiC is 5i(111)
The X-ray rotation curves when grown on a 46-shifted substrate and a 5i (100) positive substrate are shown in Figures 2 and 3, respectively.
As shown in the figure.

In Figure 2, there is an extremely sharp β when 2θ is around 35.6°.
-SiC(111) peak is observed. 77 others
A (222) peak is observed near 6.

Moreover, the small peak of Si (111) is a peak from the silicon substrate.

FIG. 2 shows that at least an azimuthally grown β-SiC layer is formed.

Compared to FIG. 2, in FIG. 3, (111) of β-SiC,
Since (200) and (400) diffraction peaks appear and include diffraction peaks of crystal planes other than the substrate surface orientation, it can be seen that no single crystal has grown.

In addition, we compared the evaluation of the epitaxial growth layer using high-speed reflection electron diffraction images, and found that streak-like spots were observed in the case of the (111) 4° shifted substrate, which indicates that the surface of β-SiC is extremely You can see how flat it is.

On the other hand, in the case of a (100) positive substrate, a ring-shaped spot image was observed, indicating that it was polycrystalline.

In the above growth, propane gas was used as the hydrocarbon, but methane (C
It is possible to use lower hydrocarbon gases such as Ht), acetylene (Cz Hz), etc.

If acetylene is used, the reaction temperature should be further increased to approximately 100°C.
It is also possible to lower the temperature.

〔Effect of the invention〕

As explained above, by applying the β-5iC epitaxial growth method of the present invention, β-SiC can be grown on a Si substrate at a low temperature of 1000° C. without using a buffer layer.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram illustrating the crystal planes related to the present invention, Fig. 2 is an X-ray diffraction image when β-SiC is grown using the growth method of the present invention, and Fig. 3 is a diagram showing ( 100) X-ray diffraction image when using silicon substrate surface, Fig. 1 Fig. 2

Claims (2)

[Claims] (1) Using a mixed gas of trichlorosilane, lower hydrocarbons, and hydrogen, <2@ under reduced pressure conditions of 1000 Pa or less
Silicon (111
) A method for epitaxially growing β-SiC, which comprises growing β-SiC in a vapor phase on a substrate. (2) The method for epitaxial growth of β-SiC according to claim (1), characterized in that the lower hydrocarbon is any one of methane, propane, and acetylene.