JPH01164797A - Method for synthesizing diamond film - Google Patents

Abstract

PURPOSE:To inhibit the selective growth of crystals and to form the title film having a smooth surface even in case of a large thickness by decomposing or evaporating a carbon source in plasma generated by electric discharge and by blowing a specified nucleus forming agent into the plasma or on a substrate. CONSTITUTION:Gas for arc discharge is fed to the gap between the cathode 1 and the anode 2 and arc discharge is caused by impressing voltage with a DC power source 3 to generate plasma. A carbon source such as an org. carbon compd. or a carbon material is decomposed or evaporated in the plasma, jetted and collided against a substrate 6 set on a substrate holder 7. At the same time, a nucleus forming agent such as a metal or diamond of 1- several mum particle size or a gaseous metal halide forming metal ions on being decomposed is blown from a nozzle 5 into the plasma or on the substrate 6 to synthesize a diamond film on the substrate.

Description

[Detailed Description of the Invention] [Summary] Regarding the method of synthesizing a diamond film, in order to prevent selective grain growth from occurring and the surface becoming rougher when the film thickness of the diamond film becomes large, a method for synthesizing a diamond film is performed using an electric discharge. A diamond film characterized by spraying solid fine particles or gaseous metal halide onto the discharge area, the plasma, or onto the substrate when a carbon source is decomposed or evaporated in the generated plasma and the diamond film is deposited on the substrate. It is configured as a synthesis method.

[Industrial application field]

The present invention relates to a method of synthesizing a diamond film, and more particularly to a method of synthesizing a diamond film of high speed and thickness for application to the electronics field.

[Conventional technology]

Conventionally, a diamond film is obtained by a CVD method in which a hydrocarbon gas is used as a carbon source and reacts by thermal decomposition.

In addition, plasma CVD method using microwaves and direct current, EACVD method using filament as the source of electron beam,
Diamond films can also be synthesized by the EACVD method, which utilizes microwaves and magnetic resonance phenomena. Due to these reasons, the application of diamond films to the electronics field is attracting attention. In particular, a method of synthesizing a diamond film that can achieve a high film formation rate using the principle of plasma spraying has recently been invented, and is approaching practical use.

[Problem that the invention seeks to solve]

With the advent of a method for synthesizing diamond films with a high deposition rate, it has become possible to synthesize diamond films with large film thicknesses, but as the film thickness increases, selective crystal growth progresses.
It was found that the surface became more uneven. the result,
When used as an electronic device, processes such as polishing are required, which is a big problem in practice.

Therefore, an object of the present invention is to provide a method for synthesizing a diamond film with a flat surface without selective crystal growth even when the film thickness is increased.

[Means for solving problems]

The present invention achieves the above object by intentionally forming a large number of crystal nuclei on a film being synthesized to suppress selective grain growth of diamond crystal grains.

That is, the present invention decomposes or evaporates a carbon source such as an organic carbon compound or a carbon material in the plasma generated by the discharge, and deposits a diamond film on the substrate in the discharge part, in the plasma, or on the substrate. A method for synthesizing a diamond film is characterized by spraying solid fine particles or gaseous metal halide.

As the solid fine particles sprayed to form new crystal nuclei, diamond or metal (eg, platinum, palladium, etc.) having a particle size of about 1 to several μm can be used. These isomers either remain as they are or are decomposed by plasma and reach the diamond film being synthesized, causing the formation of crystal nuclei. Further, while gaseous metal halides decompose to produce metal ions, halogens can be scattered, and the metal ions hit the diamond film being synthesized to create new crystal nuclei.

Such solid fine particles or gaseous metal halide may be sprayed into the discharge space, into the plasma, or onto the substrate.

Further, although the spraying may be continuous, it is preferable to spray periodically at regular intervals since this allows the generation of crystal nuclei and subsequent grain growth to be controlled as desired. The amount to be sprayed can be determined experimentally to obtain the desired crystal grain size, rather than just a portion (lj). Spray periodically.

The apparatus for generating plasma, the gas for forming plasma, the carbon source serving as the raw material for diamond, the hydrocarbon (which may be gas, liquid, or solid), carbon material, and the like may be of known type. Further, the method for spraying the crystal nucleation substance is not particularly limited, and it may be applied so that it can be uniformly dispersed on the diamond film.

[For production]

The blown solid particles or gaseous metal halides decompose or evaporate in the plasma, and in some cases, some of them do not completely decompose or evaporate and reach the diamond film being synthesized, causing crystal defects, etc. It has the function of forming a large number of crystal nuclei. This suppresses selective crystal growth.

[Example] Fig. 1 shows a diamond vapor phase synthesis apparatus for carrying out the present invention, where ■ is a cathode, 2 is an anode, 3 is a current power source, 4 is a raw material inlet, and 5 is a nucleating agent inlet. , 6 is a substrate, and 7 is a substrate holder.

The distance (arc length) between cathode 1 and anode 2 is 0.
51. Under the conditions of a current of 10 to 2 OA and a voltage of 60 to 100 V, a mixed gas of methane and hydrogen was introduced from the raw material inlet to generate plasma and deposit diamond on a silicon substrate. The flow rates of methane and hydrogen are each 0.2β/m
in and 207! /min. The substrate temperature is 800-1
The temperature was 200°C.

In this way, a diamond film with a film thickness of 0.5 mm was obtained. It was confirmed by X-ray diffraction that it was a diamond. When observed using an electron microscope, crystals with a grain size of 40 to 50 μm were formed on the surface. As a result, the surface of the diamond film was extremely uneven.

Next, under the same conditions as above, except that diamond fine particles are sprayed as a nucleating agent for 10 seconds at 100 second intervals, a diamond film is synthesized by periodically spraying the substrate at an average spraying flow rate of 0.01 (1/min). did.

A diamond film with a film thickness of 0.5 +n was obtained. It was confirmed by X-ray diffraction that it was a diamond. According to electron microscopy, diamond crystal grains have a grain size of several μm. Further, the film surface was flat with little unevenness.

〔Effect of the invention〕

According to the present invention, since a large number of crystal nuclei can be formed during the growth of a diamond film, selective growth of crystal grains is suppressed, and a smooth surface can be obtained even in a thick film, which is a practical advantage.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a diamond synthesis apparatus implementing the present invention. 1... cathode, 2... anode, 3...
Current power source, 4... Raw material inlet, 5... Nucleating agent inlet, 6... Substrate, 7... Substrate boulder-0 diamond synthesis apparatus Fig. 1 1- Cathode 2- Anode 3- Direct current Power supply 4-- Raw material inlet 5- Nucleating agent inlet 6-Substrate 7-°One substrate holder

Claims (1)

[Claims] 1. The carbon source is decomposed or evaporated in the plasma generated by the discharge, and when a diamond film is deposited on the substrate, solid fine particles or gaseous metal halide are sprayed inside the discharge part, in the plasma, or on the substrate. A method for synthesizing a diamond film.