JPH0656583A - Method for accumulation of thin diamond film - Google Patents

Abstract

PURPOSE: To provide the method of depositing a diamond thin film on a substrate at low temperatures of 450-700°C by using a chemical vapor deposition method(CVD).

CONSTITUTION: The reactive gas to be used for this method is the mixture of a chloroalkyl compound and gaseous hydrogen using as a diluent or the mixture of the chloroalkyl compound or the gaseous hydrogen, hydrocarbon or liquid hydrocarbon containing oxygen after gasification with the gaseous hydrogen. Besides, the diamond thin film having excellent crystalline degree may be obtained by adding gaseous oxygen or gaseous argon to the reactive gas.

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a chemical vapor deposition (CVD) method.
More specifically, the present invention relates to a method for producing a synthetic diamond by using a high quality diamond at a low temperature (450 to 700).
C.) and a high deposition rate.

[0002]

^2. Description of the Related Art Diamond is the hardest material on earth (HV = about 10,000 kg / mm ² ), has a significantly high thermal conductivity (about 24 watt / ° C.-cm, 5 times that of copper) and has good insulating properties. (About 10 ¹³ to 10 ¹⁶ Ωcm / 15 ° C.). Further, diamond has high wear resistance, chemical corrosion resistance, high refractive index, and low thermal expansion coefficient. Also, diamond is transparent in the ultraviolet, visible and infrared spectrum. As a result, diamond is an important material with various properties not found in other materials. Diamonds are high-tech, such as space engineering,
It has great potential for coating diamond on cutting tools, precision machining of electronic materials, semiconductor light emission and high power microwave devices. Of these, the application of diamond to electronic devices, optical devices or cutting tools is considered to be the most important use of diamond in the industry.

Under high pressure and high temperature (50,000-60,000)
The method for producing synthetic diamond at atmospheric pressure, 1300 ° C. or higher) was invented in 1955 by General Electric Company, USA. Since then, this diamond synthesis method has been industrialized and has become the major diamond manufacturing method used today. Since the cost of large synthetic diamonds is higher than that of natural diamonds, only synthetic diamonds of relatively large grain size or powder are produced by conventional methods. Also, the purity and quality of synthetic diamond is relatively low. Therefore, it is difficult for natural diamond to be completely replaced by synthetic diamond.

The chemical vapor deposition (CVD) method was developed by Soviet scientists in 1977, but requires only relatively low pressure and temperature. More chemical vapor deposition followed. For example, a hot filament CVD method, a microwave plasma CVD method, R.I. F. Plasma CVD methods and direct current plasma CVD methods have been developed by scientists in other countries such as the United States and Japan. The principles or means used in these plasma CVD methods are almost the same. That is, in these methods, diamond can be produced at low pressure and low temperature (about 1 atm, 1000 ° C. or less) and can be produced as powder / granulate or thin film. In addition, these synthetic diamonds can be deposited directly on the substrate. With the development of these improved methods for growing diamond and diamond-like thin films, the use of synthetic diamond has become increasingly important in today's industry.

[0005]

Although CVD processes that operate at low pressure and low temperature may potentially replace conventional processes, most of the new processes are still in the experimental stage. Many theories and principles need to be studied and developed into industrially available processes. To make CVD more efficient,
For example, there is a need to find new and low cost reactive gases and new substrate materials to improve diamond quality and growth rate. Also, the growth and area-maximization of the epitaxial thin film,
Industrialization of processes is also within the normal range of research in developed countries.

Microwave plasma or R.S. F. The use of plasma to activate reactive gases containing carbon to deposit diamond or diamond-like carbon has attracted interest from related industries and companies. In particular, in the last few years, attempts have been made to lower the treatment temperature for diamond precipitation and to maintain the same quality as that obtained at higher treatment temperatures. Conventional reactive gas used in the CVD method, hydrocarbon (CxHz, e.g. CH _4, C ₃ H _8, etc.), liquid hydrocarbons containing oxygen after being gasified (e.g., CH ₃ OH, C ₂ H ₅ OH, etc.) or a substance containing oxygen (eg CO, CO ₂ , H ₂ O), which are diluted with hydrogen gas and then microwave plasma, R.E. F. Activated using plasma or hot filament to deposit diamond film. However, this CVD method is about 700-1000.
It is necessary to carry out at a high temperature of ℃ to obtain a diamond thin film having good crystallinity. When the temperature is 700 ° C. or lower, the growth rate of the diamond thin film is low and the quality is unstable. In the prior art, ECR microwave vapor deposition (ECR microwave heated tungsten filament method) or pulse mode microwave vapor deposition (pulse).
d mode microwave vapor de
Only position has diamond at low temperature (45
It can be deposited at 0 to 700 ° C. However, the cost of the equipment required for this method is high, and this method cannot satisfy the requirements of both high quality and high deposition rate of the diamond thin film.

In an experiment conducted by the inventor of the present invention, when a diamond thin film is deposited on a silicon substrate by using a microwave plasma CVD method, a diamond having good crystallinity and high purity (by Raman spectrum analysis) is used. A thin film was obtained. In this case, the deposition rate and crystallographic direction of the diamond thin film are greatly influenced by the crystallographic direction and temperature of the substrate. Whatever CVD method and reactive gas is used, the temperature should be in the range of 700 to 1000 ° C. to obtain a diamond thin film having excellent quality at a high deposition rate. That is, the substrate temperature is 70
Below 0 ° C., it is difficult to produce diamond thin films with good crystallinity at high deposition rates.
Therefore, the production of synthetic diamond using the CVD method is
It is basically limited to its high processing temperature. Furthermore, since the substrate is easily destroyed by high temperatures, synthetic diamond thin films using the CVD method can only be deposited on substrates that are resistant to high temperatures (such as WC material). In other words, this method limits the materials that can be used as the substrate.

Accordingly, it is an object of the present invention to deposit a high quality diamond thin film on a substrate at high speed and low temperature (450-700).
To provide a mixture of reactive gases that can be produced at.

[0009]

The reactive gas used in the present invention is a chloroalkyl compound (C
HxCly). The reactive gas is a chloroalkyl compound or chlorine gas, and a hydrocarbon (CxHy such as CH ₄ ) or a liquid hydrocarbon containing oxygen after being gasified (such as CH ₃ OH and C ₂ H ₅ OH). And a hydrogen gas used as a diluent. Microwave plasma, R.S. F. Activate the reactive gas using plasma or hot filament CVD method,
Then, a diamond thin film is deposited on the substrate while maintaining the substrate temperature at 700 ° C. or lower.

Further, an appropriate amount of oxygen gas or argon gas can be added to the reactive gas to improve the quality of the diamond thin film.

In the present invention, the diamond thin film is
Low temperature (about 450-700 ° C) and high deposition rate (about 3-
In 6 hours), it can be suitably deposited on the substrate without using an expensive device. That is, microwave plasma, R.W. F. CVD of plasma, hot filament, etc.
The method is suitable for use in the present invention. Since the processing temperature can be lowered by about 200 ° C., a material other than a material resistant to high temperature can be used as the substrate material.

A feature of the present invention is that a chloroalkyl compound (CHxCly) or chlorine gas is present in the reactive gas. In addition, the reactive gas can be appropriately mixed with hydrocarbon or liquid hydrocarbon containing oxygen after gasification, and oxygen gas or argon gas.

In the reactive gas according to the present invention, the volume ratio of the chloroalkyl compound to hydrogen gas is 3% or less. When adding hydrocarbons to the reactive gas, the atomic ratio of carbon atoms to chlorine atoms in the reactive gas is 0.2-10. When adding oxygen gas or argon gas, the volume ratio of oxygen gas: hydrogen gas is 3%
Below, the volume ratio of argon gas: hydrogen gas is 10%
Below.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. (Example 1) A microwave plasma CVD apparatus for depositing a diamond thin film is shown in FIG. In the figure, the reference numerals are as follows. 1 ... Microwave generator 2 ... Waveguide 3 ... Reaction chamber 4 ... Substrate 5 ... Substrate holder 6 ... Decompression system 7 ... Gas pipe 8, 9 ... Regulator 10, 11 ... Gas supply system

The substrate (10 mm × 10 mm) was polished and placed on an annular substrate holder having a diameter of 30 mm. This annular substrate holder is arranged in the center of a quartz reactor having an inner diameter of 47 mm. Substrate 6 using microwave plasma
Heat to a temperature of 50 ° C and increase the pressure in the reactor to 3.3 kPa.
Held in. The reactive gas used in this example is H ₂ −.
CHCl ₃ system, in which case the flow rate of hydrogen gas is 20
The flow rate of 0 ml / min and CHCl ₃ was 1 ml / min. The reaction was carried out for 3 hours as a total reaction time, and thus a 1.2 μm thick diamond thin film (not diamond grains) was obtained. An SEM micrograph of this diamond thin film is shown in FIG. The diamond thin film had good crystallinity in its faced structure.

(Example 2) The same treatment was carried out using the same apparatus as in Example 1 except that a H ₂ --CH ₄ --CHCl ₃ -based reactive gas was used. H ₂ flow rate is 200 ml / mi
The flow rate of n and CH ₄ was 5 ml / min, and the flow rate of CHCl ₃ was 1 ml / min. The substrate temperature was 480 ° C., the pressure was maintained at 2.0 kPa, and the total reaction time was 6 hours. As shown in FIG. 3, this diamond thin film had a good crystallinity and in this way an excellent deposition was obtained.

Example 3 H ₂ —CH ₄ —CHCl ₃ —O ₂
The same processing was performed using the same apparatus as in Example 1 except that the system reactive gas was used. H ₂ flow rate is 200 ml /
The flow rate of min and CH ₄ was 10 ml / min, the flow rate of CHCl ₃ was 1 ml / min, and the flow rate of O ₂ was 1 ml / min. The substrate temperature is 560 ° C. and the pressure is 2.0 kPa.
And the total reaction time was 6 hours. Figures 4, 5 and 6
As shown in Figure 3, the diamond thin film had good crystallinity and thus excellent deposition was obtained.

(Example 4) H ₂ --CH ₄ --CHCl ₃ --A
The same process was performed using the same apparatus as in Example 1 except that the r-type reactive gas was used. H ₂ flow rate is 200 ml
/ Min, the flow rate of CH ₄ was 5 ml / min, the flow rate of CHCl ₃ was 1 ml / min, and the flow rate of O ₂ was 8 ml / min. The substrate temperature is 545 ° C. and the pressure is 2.0 kPa.
And the total reaction time was 6 hours. As shown in FIG. 7, the diamond thin film had a good crystallinity and in this way an excellent deposition was obtained.

Although the present invention has been described above with reference to the embodiments with reference to the drawings, the present invention is not limited thereto and various modifications can be made within the scope of the gist of the present invention.

[0020]

As described above, according to the present invention,
Due to the use of a specific reactive gas mixture, a high quality diamond film can be deposited on the substrate at high speed and low temperature (45
It can be manufactured at 0 to 700 ° C.).

[Brief description of drawings]

FIG. 1 is a schematic view of a microwave plasma CVD apparatus.

FIG. 2 is an SEM micrograph showing the crystal structure of the diamond thin film of Example 1.

FIG. 3 is an SEM micrograph showing a crystal structure of a diamond thin film of Example 2.

FIG. 4 is an SEM micrograph showing the crystal structure of the diamond thin film of Example 3.

5 is a diagram showing a Raman spectrum of a diamond thin film of Example 3. FIG.

FIG. 6 is a diagram showing an X-ray diffraction pattern of a diamond thin film of Example 3.

FIG. 7 is an SEM micrograph showing the crystal structure of the diamond thin film of Example 4.

[Explanation of symbols]

 1 Microwave generator 2 Waveguide 3 Reaction chamber 4 Substrate 5 Substrate holder 6 Decompression system 7 Gas pipe 8, 9 Regulator 10, 11 Gas supply system

Claims (20)

[Claims] 1. When depositing a diamond thin film on a substrate using a chemical vapor deposition (CVD) method, a reactive gas is activated, and the diamond thin film is deposited on the substrate at 450 to 700 ° C. Is chloroalkyl (CH
xCly) Compound and hydrogen gas mixture, method for depositing diamond thin film. 2. The deposition method according to claim 1, wherein the volume ratio of the chloroalkyl compound to hydrogen gas is 3% or less. 3. The chloroalkyl compound is CHCl ₃ ,
The deposition method according to claim 1, wherein the compound is a compound selected from the group consisting of CH ₂ Cl ₂ and CCl ₄ . 4. The method of claim ₃ , wherein the chloroalkyl compound is CHCl ₃ . 5. When depositing a diamond thin film on a substrate by using a chemical vapor deposition method (CVD), a reactive gas is activated, and the diamond thin film is deposited on the substrate at 450 to 700 ° C. Is a mixture of a chloroalkyl compound or chlorine gas, a hydrocarbon or a liquid hydrocarbon containing oxygen after being gasified, and a mixture of hydrogen gas, and a method for depositing a diamond thin film. 6. The deposition method according to claim 5, wherein the atomic ratio of carbon atoms to chlorine atoms in the reaction gas is 0.2 to 10. 7. The deposition method according to claim 5, wherein the volume ratio of the chloroalkyl compound to hydrogen gas is 3% or less. 8. The chloroalkyl compound is CHCl ₃ ,
The deposition method according to claim 5, wherein the compound is a compound selected from the group consisting of CH ₂ Cl ₂ and CCl ₄ . 9. The deposition method according to claim 8, wherein the chloroalkyl compound is CHCl ₃ . 10. The deposition method according to claim 5, wherein the hydrocarbon is CH ₄ . 11. The deposition method according to claim 1, wherein the liquid hydrocarbon containing oxygen after being gasified is a compound selected from the group consisting of CH ₃ OH and C ₂ H ₅ OH. . 12. When depositing a diamond thin film on a substrate using a chemical vapor deposition method (CVD), a reactive gas is activated, and the diamond thin film is deposited on the substrate at 450 to 700 ° C. Is a chloroalkyl compound or chlorine gas, hydrocarbon or liquid hydrocarbon containing oxygen after being gasified, oxygen gas or argon gas,
And a mixture of hydrogen gas and a method for depositing a diamond thin film. 13. The deposition method according to claim 12, wherein the volume ratio of the chloroalkyl compound to hydrogen gas is 3% or less. 14. The deposition method according to claim 12, wherein the atomic ratio of carbon atoms to chlorine atoms in the reaction gas is 0.2 to 10. 15. The deposition method according to claim 12, wherein the volume ratio of oxygen gas to hydrogen gas is 3% or less. 16. The volume ratio of argon gas to hydrogen gas is 10% or less.
The deposition method described. 17. The chloroalkyl compound is CHC.
13. The deposition method according to claim 12, which is a compound selected from the group consisting of l ₃ , CH ₂ Cl ₂ and CCl ₄ . 18. The deposition method of claim 17, wherein the chloroalkyl compound is CHCl ₃ . 19. The deposition method according to claim 12, wherein the hydrocarbon is CH ₄ . 20. The deposition method according to claim 12, wherein the liquid hydrocarbon containing oxygen after being gasified is a compound selected from the group consisting of CH ₃ OH and C ₂ H ₅ OH. .