JP2584480B2 - Diamond film manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a diamond film having a color tone close to natural diamond on a substrate.

[Conventional technology]

Since diamond has high hardness, is highly insulating, and is chemically stable, it has recently been developed for use as an electronic material such as an IC substrate in addition to tools.

Artificial diamonds used for these applications are manufactured industrially from carbon using ultra-high pressure equipment, and recently, a thin film of diamond is synthesized from hydrocarbons and hydrogen on a substrate heated to 700 to 1200 ° C. Many vapor-phase synthesis methods for coating have been proposed.

As a method for producing a diamond film from this gas phase,
Preheating a mixed raw material gas of hydrocarbons such as methane and hydrogen with heated metal filament (thermal CVD method: Japanese Patent Application No. 56-1)
No. 89423), a method of exciting the above mixed material gas by microwave non-polar discharge (see Japanese Patent Application No. 56-204321), and a method of mixing hydrogen excited by high frequency application with hydrocarbons (Japanese Patent Application No. Reference is made to JP-A-57-12966).

For example, in a typical thermal CVD method, a mixed raw material gas of hydrocarbon and hydrogen is preheated with a metal filament (generally, a tungsten filament) heated to about 2000 ° C.
Diamond is deposited as a thin film on a substrate heated to 0 to 800 ° C. It is known that a diamond film obtained by this method has a crystal structure very similar to natural diamond by electron diffraction, X-ray diffraction, Raman spectroscopy, or the like.

[Problems to be solved by the invention]

As described above, it has become possible to form a diamond film on a substrate by a vapor phase synthesis method such as a thermal CVD method, but any diamond film obtained by such a conventional technique has a gray or black color. The color tone was far from the colorless and transparent of natural diamond.

The present invention has been made in view of such conventional circumstances, and has as its object to form a diamond film having a color tone as close as possible to natural diamond on a substrate.

[Means for solving the problem]

As a means for achieving the above object, the method for producing a diamond film of the present invention comprises the steps of: synthesizing a diamond film on a substrate from a raw material gas of hydrocarbon and hydrogen; And treating with atomic hydrogen while maintaining the temperature.

As a method for generating atomic hydrogen, a method in which reduced-pressure hydrogen is heated to about 2000 ° C. or higher with a metal filament such as tungsten, or a method in which plasma is generated by glow discharge is preferable.

[Action]

There have been various theories as to the reason why the diamond film formed on the substrate by a vapor phase synthesis method such as a thermal CVD method has a gray or black color, and the details are unknown.

However, the present inventors presumed that the reason for this was that a small amount of carbon other than diamond was precipitated, and tried to remove the carbon other than diamond to complete the present invention.

That is, in the method of the present invention, carbon other than diamond deposited in a diamond film formed on a substrate by a vapor phase synthesis method such as a thermal CVD method is etched with atomic hydrogen. Although carbon of diamond is hardly etched by atomic hydrogen, carbon other than diamond is etched and removed by atomic hydrogen in a heated state, and the gray or black diamond film is decolorized to a color close to white.

The temperature of the diamond-coated substrate during treatment with atomic hydrogen should be 500 ° C. to 1900 ° C. If the temperature is less than 500 ° C., no decolorizing effect of the diamond film is observed, and 1900 ° C.
If the temperature exceeds ℃, the transformation from diamond to graphite cannot be ignored.

The processing time with atomic hydrogen can be appropriately selected depending on the temperature of the diamond-coated substrate, the concentration of atomic hydrogen, the thickness of the diamond film, and the like. However, in the case of a usual film thickness of 1 to 20 μm, generally, a treatment time of 5 minutes to 5 hours is preferable, and a treatment time of less than 5 minutes is insufficient for the decolorizing effect by etching of carbon other than diamond, Conversely, if the time exceeds 5 hours, the etching of the diamond cannot be ignored.

〔Example〕

The Si substrate scratched with diamond abrasive was placed in a CVD apparatus and heated to 850 ° C. In this device, tungsten filament placed 10 mm away from the Si substrate
Heated to 00 ° C, 80t of 1cc / min methane and 99cc / min hydrogen
It was supplied by orr, and diamond was deposited on the Si substrate for 3 hours.

The obtained diamond film has a thickness of about 5 μm,
Raman spectroscopy confirmed that it had a diamond crystal structure, but the color was gray to black.

Si coated with this gray or black diamond film
The substrate was placed again in the CVD apparatus and heated to 1050 ° C. Hydrogen of 100 cc / min was introduced into the apparatus at 80 torr, and was brought into contact with a tungsten filament heated to 2100 ° C. to generate atomic hydrogen, and a diamond film was treated in the atomic hydrogen for 30 minutes. The diamond film on the substrate removed from the apparatus after the treatment was decolorized and exhibited almost white.

〔The invention's effect〕

According to the present invention, a diamond film having a color tone much closer to natural diamond than before can be formed on a substrate from a gas phase.

Claims (1)

(57) [Claims] The present invention is characterized in that after a diamond film is synthetically coated on a substrate from a raw material gas of hydrocarbon and hydrogen, the diamond-coated substrate is treated with atomic hydrogen while maintaining the temperature at 500 to 1900 ° C. Method for producing a diamond film.