JP3131773B2 - Preparation method of SiC thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for forming a SiC thin film.

[0002]

2. Description of the Related Art SiC is a compound semiconductor having characteristics such as a wide band gap, high electron mobility, high heat resistance, abundant resources of constituent elements, and low concern about environmental pollution. It is a material expected to be applied as a next-generation electronic device, an electronic device capable of high-speed and high-temperature operation, a photovoltaic device, and the like. In particular, S formed on a silicon substrate
Since the iC thin film can inherit the current silicon technology, it is a material that is required to be put to practical use also from the viewpoint of the development cost of industrial technology. It is also required to grow epitaxially on a silicon substrate in order to optimally extract material properties. As a method of forming the SiC thin film, there are various CVD methods, sputtering methods, various MBE methods, and the like.

[0003]

All of the above-mentioned conventional methods for forming a SiC film require heating of the substrate (at 600 to 1200 ° C. or higher). This is because the bond between Si and C is a covalent bond, so that both the chemical bond formation energy and the diffusion energy for epitaxial crystal growth are large. However, since the lattice constant of SiC and Si has a difference of about 20% (lattice mismatch) and the coefficient of linear thermal expansion thereof also has a difference of 8%, the thin film formation at high temperature requires the thermal It has been predicted that distortion will occur, which will lead to deterioration of element characteristics and mechanical damage, and thus development of a low-temperature thin film forming technique has been required. The present invention has been made to solve the drawbacks of the conventional method, and an object of the present invention is to use an ion irradiation technique to achieve low-temperature formation of a chemical bond between Si-C and low-temperature epitaxial growth of the formed SiC. It is an object to provide a method that makes it possible.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the preparation of a SiC thin film, and have found that
By irradiating high energy ions to the two-component system of carbon, it is possible to reduce S by electronic energy excitation by inelastic scattering from high energy ions without heating the substrate.
The inventors have found that an iC thin film can be formed and grown, and have completed the present invention.

The present invention, carbon film or a carbon deposited on a silicon substrate - silicon mixture film or the silicon substrate was implanted carbon ions, by irradiating a high energy ions, without substrate heating, high energy
For electronic energy excitation by inelastic scattering from ions
This method excites a reaction between Si and C to form a SiC compound. As a method of forming a carbon film or a carbon-silicon mixed film, for example, as a carbon film,
The silicon film can be formed by simultaneous vapor deposition or alternate vapor deposition by using electron beam vapor deposition, Knudsen cell, or the like by using direct current heating or electron beam vapor deposition of carbon, and by using electron beam vapor deposition or Knudsen cell. In addition, a mixed film can be formed by thermal decomposition of an organic metal containing Si and C as components, but does not particularly depend on a film forming method.
What is necessary is just to set the high energy ion species and energy value according to the thickness of a thin film.

Further, the present invention provides a method of irradiating the thus formed SiC thin film or an amorphous or non-oriented SiC thin film formed on a silicon substrate by other methods with high energy ions. Due to inelastic scattering from high energy ions without substrate heating
A method for producing a SiC thin film is characterized in that these thin films are epitaxially grown on a substrate silicon by electronic energy excitation . Amorphous or unoriented SiC
As a method for forming a thin film, there are a sputtering method, a CVD method using an organic metal such as methylsilane, and the like.

In the method of the present invention, since the substrate is not required to be heated, it is possible to suppress the mechanical strain caused by the contraction due to the difference in the thermal expansion coefficient. Further, thermal diffusion at the interface with the substrate silicon can also be suppressed. It is known that carbon forms a solid solution in silicon at high temperatures. SiC
In the case of developing an element using a semiconductor junction of / Si, a change in characteristics on the Si side due to solid solution of carbon causes deterioration of the element function. However, the method of the present invention does not require that the substrate is not heated. If the characteristics required for the semiconductor element allow substrate heating, it is also possible to use substrate heating in combination. In this case, there is an advantage that the ion energy to be irradiated and the irradiation amount can be reduced.

[0008] The lower limit energy that can be used as high energy ions depends on the type of ions and the thickness of the thin film, but the inelastic scattering energy loss and the elastic scattering energy loss predicted by calculation based on LSS theory. It is necessary for the ratio to exceed 5, and preferably to exceed 10. In order to realize epitaxial growth, this ratio must be maintained at the interface between the SiC thin film and the substrate. Therefore, as the thickness of the SiC thin film increases, higher energy is required accordingly. On the other hand, since this ratio increases as the energy increases, there is no upper limit of the energy that can be used in principle. In addition, since this ratio decreases as the mass of ions used increases, relatively high energy is required for heavy ions.

Any kind of ion can be used as long as the above-mentioned ratio exceeds 5, except for hydrogen ions, where collision of energetic particles of carbon-hydrogen has a possibility of a nuclear reaction, so that it is practically possible. Not preferred. Therefore, 20 keV in helium which is the lightest element except hydrogen is the lower limit energy. In selecting an actual ion energy, it is necessary to consider the influence of lattice distortion of the substrate silicon due to elastic scattering of irradiation ions on the crystallinity and surface smoothness of the SiC thin film on the surface.

In order to carry out the method of the present invention, the following apparatus can be used. FIG. 1 shows the outline. An ion generator 1 capable of generating helium ions of 20 keV or more as ion energy. A vacuum chamber 3 connected to the ion generator 1 and the evacuation device 2. Although the degree of vacuum depends on the energy of the ion generator 1, it is usually 10 ^-4 Pa or more in order to generate uncertainty due to ion energy attenuation due to scattering with residual gas and to prevent contamination from vacuum. desirable. Sample holding device 4 in vacuum chamber 2.
This sample holding device 4 may be any device that can hold a carbon source on silicon, a carbon-silicon mixed film, and the like, and can be arranged so that the film can be irradiated with ions. Carbon and silicon film forming apparatus 5. The carbon film on silicon, the carbon-silicon mixed film, and the like only need to have a mechanism capable of being introduced into the vacuum chamber 3 from the outside. However, in order to prevent impurities from entering the atmosphere, the carbon film, It is preferable to provide a thin film forming apparatus capable of forming a silicon mixed film or the like.

[0011]

EXAMPLE 1 A 1-nm thick carbon thin film formed on a silicon (100) substrate by electron beam evaporation was irradiated with 2 MeV argon ions.
By irradiating at least 10 ¹⁵ ions / cm ² , an amorphous SiC thin film was obtained at room temperature without heating the substrate. By continuing the ion irradiation, an amorphous SiC thin film was obtained as a crystalline SiC thin film having an epitaxial relationship with the substrate silicon (100).

Example 2 A 2-monolayer carbon thin film formed on a silicon (100) substrate by electron beam evaporation was irradiated with 200 keV helium ions at a dose of 1 × 10 ¹⁴ ions / cm ² or more, so that the room temperature was lowered. An amorphous SiC thin film was obtained without heating the substrate. By continuing ion irradiation, amorphous Si
As the C thin film, a crystalline SiC thin film having an epitaxial relationship with the substrate silicon (100) was obtained.

EXAMPLE 3 A multilayer film of a carbon film (thickness 1 nm) and a silicon film (thickness 1 nm) is formed on a silicon (100) substrate by electron beam evaporation, and 2 MeV argon ions are applied to the silicon film (1 ×).
By irradiating 10 ¹⁵ ions / cm ² or more, an amorphous SiC thin film was obtained at room temperature without heating the substrate. By continuing the ion irradiation, an amorphous SiC thin film was obtained as a crystalline SiC thin film having an epitaxial relationship with the substrate silicon (100).

Example 4 A 2MeV argon ion of 5 × 10 ¹⁵ ions / s was applied to a non-oriented polycrystalline SiC thin film (5 nm in thickness) formed on a silicon (100) substrate by a pyrolysis method of ethylene.
Irradiation of not less than ² cm ² yielded a crystalline SiC thin film having an epitaxial relationship with the substrate silicon (100) at room temperature without substrate heating.

[0015]

According to the method of the present invention, it is possible to form SiC, which is a next-generation semiconductor material, at room temperature as an epitaxial thin film on a silicon substrate.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus used to carry out the method of the present invention.

Continuation of the front page (56) References JP-A-6-199572 (JP, A) JP-A-61-191013 (JP, A) JP-A-1-238111 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) C23C 14/00-14/58 C01B 31/36 H01L 21/20-21/205

Claims (5)

(57) [Claims] 1. A carbon film or a carbon deposited on a silicon substrate - the silicon mixed film or a silicon substrate implanted carbon ions, by inelastic scattering of high energy ions that by the irradiation with high-energy ions Electric
A method for producing a SiC thin film, characterized in that a reaction between silicon and carbon is excited by excitonic energy excitation to form a Si-C bond and grow a SiC thin film. Wherein the amorphous or unoriented SiC thin film is present on a silicon substrate, inelastic scattering from the high energy ions that by the irradiation with high-energy ions
Growing a SiC thin film having an epitaxial relationship with a substrate by electronic energy excitation by the method. 3. As high energy ions, 10 keV
3. The method according to claim 1, wherein ions having the above energies are used. 4. The method for producing a SiC thin film according to claim 1, wherein ions having a mass equal to or greater than helium ions are used as high energy ions. 5. The method for producing a SiC thin film according to claim 1, wherein high energy ions are irradiated without heating the substrate.