JPH0761896A - Method for synthesizing diamond by vapor phase process and synthesizer therefor - Google Patents

Abstract

PURPOSE:To obtain in a vapor phase high-grade diamond film with uniform thickness by using carbonized tantalum filaments as hot filaments. CONSTITUTION:In the subject synthesis using hot filaments as excitation means, tantalum carbide filaments 3 prepared by carbonizing part or the whole of tantalum filaments is used as an excitation source, and a feedstock gas 2 for synthesizing diamond (e.g. a mixed gas of an organic compound and hydrogen) is brought into contact with the filaments 3 at a flow rate of >1m/sec. With such a scheme that the flow of the stock gas come into contact with the filaments in the flow direction, the tendency of increasing diamond film thickness per unit time is remarkable, enabling a diamond film of large area with uniform thickness to be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase diamond synthesizing method, and more particularly to a synthesizing method and a synthesizing apparatus in which a tantalum filament is used as a hot filament and a raw material gas for synthesizing diamond is brought into contact with the filament at high speed. It is a thing.

[0002]

2. Description of the Related Art A method of synthesizing a vapor phase diamond is to synthesize a raw material carbon compound gas such as hydrocarbon, alcohol or acetone by mixing hydrogen gas with an exciting means. At present, there are various methods for exciting gas, which are roughly classified into a method using a heating filament, a method using a microwave, a method using a high frequency, and other special ones such as glow discharge, arc discharge,
There are a sputtering method, an ion beam method, an ultraviolet ray irradiation and the like, which is a method of decomposing and exciting the mixed gas by these exciting means to deposit diamond on a substrate or the like. Also known is a method of adding water vapor, oxygen, carbon monoxide or the like to the raw material gas.

[0003]

In the vapor phase diamond synthesizing method using a hot filament as an exciting means, the diamond deposition rate is generally several μm / hr, and further improvement is required in terms of uniformity and large area. ing. On the other hand, regarding the filament material, Japanese Patent Application No. 63-187353 discloses a method of adjusting a tantalum filament and a method of synthesizing a diamond, but further high-speed deposition and homogenization were required. The present invention aims to solve these problems.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above object, and as a result, after passing a raw material gas for diamond synthesis through a highly excited filament at high speed, a deposition substrate The inventors have found that the solution can be achieved by contacting with, and have completed the present invention.

Conventionally, in the diamond synthesis method using the hot filament method, the influence on the deposition rate, the uniformity, and the diamond quality by the feed gas introduction position and the contact flow velocity to the filament has been very low. However, it has been confirmed that the deposition rate and quality change significantly when the source gas is brought into contact with the highly excited hot filament at a high flow rate. When the excitation of the filament is low, it is cooled by the raw material gas having a high flow rate, and on the contrary, it becomes difficult to synthesize diamond, and DLC or graphite is deposited. Further, the filament temperature is lowered by the raw material gas, pyrolytic carbon is deposited on the end of the filament, and resistance heating of the filament is reduced, so that stable deposition is impossible.

W generally used in the hot filament method
For filaments, the filament temperature is at most 2200 ° C
Therefore, the flow rate and flow velocity of the raw material gas to be contacted are limited to a narrow range, which is not practical. When a carbonized Ta filament is used, it is possible to set the filament temperature near 3000 ° C., the flow rate of the raw material gas to be brought into contact with the filament can be widened, and pyrolytic carbon deposition on the end of the filament hardly occurs, which is stable for a long time. The reaction can take place. It was confirmed that there is a completely new range of conditions for the hot-filler method that can realize high precipitation rate and high-quality contradictory precipitation characteristics that could not have been predicted by the conventional hot-filler method. The filament temperature is 1800 ° C or higher, preferably the filament temperature is 2
It is 200 ° C or higher. Pressure range in the reaction tank is 1 to 1000
Torr, preferably 10 to 200 torr.
If the pressure is too low, the film formation rate will be reduced, and if the gas pressure is high, the mass will be large, and the filament structure material is likely to be deformed. The diamond film can be obtained with high quality and film thickness uniformity by the raw material spraying method because it is in contact with the highly excited filament,
It is considered that the radical species and atomic hydrogen generated in high concentration by decomposition and dissociation can reach the substrate in high concentration without being deactivated. Further, it is considered that the thermoelectrons emitted from tantalum carbide and the generation spectrum are effective for generation of radical species and atomic hydrogen that contribute to diamond formation and energy retention, as compared with a commonly used tungsten filament.

When a plurality of exciting filaments are installed in the flow direction of the raw material gas, the diamond film thickness per time tends to increase remarkably. Suitable for making area diamond film.

The flow velocity described in the specification of the present invention is, for convenience, a value that takes into consideration the reaction pressure difference in the initial flow velocity of the raw material gas nozzle in the standard state. The effects of gas temperature rise and decomposition / dissociation are excluded.

An example for carrying out the method according to the invention with the device according to the invention according to FIG. 1 is shown. A mixed gas of an organic compound and hydrogen having a flow rate of 1 m / sec or more, which is discharged from the raw material spraying nozzle 2, contacts the tantalum filament 3 in a high temperature excited state,
It passes and becomes a diamond film on the silicon substrate 4. As the flow velocity increases, the film formation rate in the thickness direction tends to increase,
In that case, it is necessary to increase the temperature of the tantalum filament. Further, when a uniform large-area film is required, the filament is arranged so as to face the raw material spray nozzle, but a uniform film is obtained by spraying the raw material in the center, but the raw material spraying flow rate in this case is 1 to 50 m / sec
The film thickness can be made uniform.

[0010]

【Example】

Example 1 A diamond film was synthesized by using a single filament in the apparatus shown in FIG. The specifications of the device are as follows. Reaction tank: height 500 mm, diameter 400 mm, internal volume 60
Liter, stainless steel Raw material spray nozzle: 1/8 inch, stainless steel tube Tantalum filament: wire diameter 0.4mmφ, coil diameter 2
mmφ, 15 windings Substrate: Silicon 20 × 40 × 1 mm Substrate support: Substrate temperature control function (not shown)

Filament temperature: 2 using the above apparatus
400 ° C., reaction pressure: 100 torr, CH ₄ / H ₂ : 2.
0%, raw material spraying initial velocity 9.3 m / sec, substrate temperature 8
50 ° C, distance between raw material spray nozzle and filament: 3
0 mm, filament-substrate distance: 3 mm 3
Synthesized over time.

As a result, an oval (5 × 10 mm) film having a thickness of 34.6 μm was deposited. Only a sharp peak at 1333 cm ^-1 was detected by Raman spectroscopy.

Comparative Example 1 Of the synthesis conditions of Example 1, tungsten was used instead of the filament. At 2400 ° C., the central part of the filament sags, and the deposited state of the diamond film became a donut-shaped deposited film with no diamond in the central part where i-carbon was mixed. Although the filament temperature was lowered to 2100 ° C. for synthesis, carbon was attached to the filament when the synthesis time exceeded 1 hour, and the synthesis became impossible after about 1 hour and 30 minutes.

Example 2 Synthesis was carried out under the same conditions as in Example 1 except for the following. There are two tantalum filaments on the upper and lower sides, and the material spraying nozzle-upper filament 30 mm, the upper and lower filament 3 mm, the lower filament-substrate 3 m.
At m, the initial velocity is 30 m / sec. The diamond deposition film after synthesis had an elliptical shape of 6 × 12 mm and had a film thickness distribution within 75 ± 5 μm. As in Example 1, the measurement by Raman spectroscopy showed only a sharp peak at 1333 cm ⁻¹ .

[0015]

EFFECTS OF THE INVENTION According to the present invention, high-speed diamond film formation in the thickness direction and large-area uniform film formation are possible, and the selection range is expanded from the viewpoint of application.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an apparatus used in the present invention.

[Explanation of symbols]

 1 Reaction Tank 2 Raw Material Spraying Nozzle 3 Tantalum Filament 4 Substrate 5 Substrate Support 6 Exhaust Pipe

Claims (4)

[Claims] 1. A method for synthesizing a vapor phase diamond using a hot filament as an exciting means, wherein a tantalum filament, which is a part or all carbonized as a filament, is used as an excitation source, and a raw material gas for diamond synthesis has a flow rate of 1
A method for synthesizing a vapor-phase method diamond, which comprises contacting at m / sec or more. 2. The method for synthesizing a vapor phase diamond according to claim 1, wherein the flow of the raw material gas is in contact with a plurality of filaments in the flow velocity direction. 3. A vapor phase diamond synthesizing method using a hot filament as an exciting means, wherein a tantalum filament having a part or all carbonized as a filament is used as an exciting source, and a raw material gas for synthesizing diamond has a flow rate of 1
An apparatus for synthesizing vapor phase diamond, characterized in that they are contacted at m / sec or more. 4. The apparatus for synthesizing a vapor grown diamond according to claim 3, wherein the flow of the raw material gas comes into contact with a plurality of filaments in the flow velocity direction.