JPH0829999B2 - Diamond film synthesis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] Regarding a method for synthesizing a diamond film, when the thickness of the diamond film becomes large, it is generated by an electric discharge in order to prevent selective grain growth and to make the surface rough. In the process of decomposing or evaporating the carbon source in the plasma to deposit the diamond film on the substrate, solid fine particles or a gas metal halide is sprayed on the discharge part, the plasma or the substrate. Configure as a synthesis method.

[Industrial applications]

The present invention relates to a method for synthesizing a diamond film, and more particularly to a method for synthesizing a high-speed high-thickness diamond film 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 is reacted by thermal decomposition. In addition, a diamond film is also synthesized by a plasma CVD method using microwave or direct current, an EACVD method using a filament as an electron beam generation source, an ECRCVD method utilizing microwave and magnetic resonance phenomena. Due to these, the application of the diamond film to the electronics field is drawing attention. In particular, recently, a method for synthesizing a diamond film, which can obtain a large film forming rate by utilizing the principle of plasma spraying, has been invented, and is approaching practical use.

[Problems to be solved by the invention]

With the advent of a method for synthesizing a diamond film with a large film formation rate, it has become possible to synthesize a diamond film with a large film thickness, but as the film thickness increases, selective crystal growth proceeds and surface irregularities become severe. Was found. As a result, when used as an electronic device, a step such as polishing is required, which is a serious problem in practical use.

Therefore, it is an object of the present invention to provide a method for synthesizing a diamond film having a flat surface without selective crystal growth even if the film thickness becomes large.

[Means for solving problems]

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

That is, the present invention, while introducing a gas between the anode and the cathode, to apply a DC voltage to perform arc discharge,
A method for synthesizing a diamond film using direct current arc discharge plasma, in which the generated plasma is ejected from a nozzle as a plasma jet and irradiated onto a substrate to form a diamond film, which is a carbon source in the plasma generated by direct current arc discharge. The solid particles selected from diamond, platinum or palladium are continuously or intermittently sprayed in the discharge part, in plasma, or on the substrate during the decomposition or evaporation of the diamond to deposit the diamond film on the substrate. And a method for synthesizing a diamond film.

The particle size of the solid fine particles sprayed to form new crystal nuclei may be 1 to several μm. These solids, as they are, or by being decomposed by plasma, reach the diamond film being synthesized, which causes the formation of crystal nuclei.

Such solid fine particles may be sprayed on the discharge space, in plasma, or on the substrate. Further, the spraying may be continuous, but it is preferable to spray the powder periodically with a constant time interval since the generation of crystal nuclei and the subsequent grain growth can be controlled as desired. The amount to be sprayed is not uncertain, and may be determined experimentally so as to obtain a desired crystal grain size. For example, an amount such that one crystal nucleus is formed per 1 μm ^□ is periodically set at an appropriate interval. To spray.

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

[Action]

The sprayed solid fine particles decompose or evaporate in the plasma, and in some cases, do not completely decompose or evaporate and reach the diamond film during synthesis to generate many crystal nuclei due to crystal defects. Has the function of forming. Thereby, selective crystal growth is suppressed.

〔Example〕

FIG. 1 shows a diamond vapor phase synthesis apparatus for carrying out the present invention, in which 1 is an anode, 2 is a cathode, 3 is a DC power source, 4 is a raw material inlet, 5 is a nucleating agent inlet, and 6 is a substrate. , 7 are substrate holders.

The distance (arc length) between quad 1 and anode 2 is 0.
Under conditions of 5 mm, current 10 to 20 A, voltage 60 to 100 V, a mixed gas of methane and hydrogen was introduced from a raw material inlet to generate plasma and deposit diamond on a silicon substrate. The flow rates of methane and hydrogen were 0.2 l / min and 20 l / min, respectively. The substrate temperature was 800 to 1200 ° C.

Thus, a diamond film having a thickness of 0.5 mm was obtained. It was confirmed to be diamond by X-ray diffraction. Observation with an electron microscope revealed that crystals having a particle 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, diamond fine particles as a nucleating agent were sprayed on the substrate periodically at an average spraying flow rate of 0.01 / min in a mode of spraying for 10 seconds at 100 second intervals to synthesize a diamond film.

A diamond film having a thickness of 0.5 mm was obtained. It was confirmed to be diamond by X-ray diffraction. Observation by an electron microscope reveals that the crystal grains of diamond have a grain size of several μm. The surface of the film was flat with little unevenness.

〔The invention's effect〕

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

[Brief description of drawings]

FIG. 1 is a schematic diagram of a diamond synthesizing apparatus for carrying out the present invention. DESCRIPTION OF SYMBOLS 1 ... Cathode, 2 ... Anode, 3 ... Current power supply, 4 ... Raw material inlet, 5 ... Nucleating agent inlet, 6 ... Substrate, 7 ... Substrate holder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Sasaki, Kenichi Sasaki, Kanagawa Prefecture, Nakahara-ku, Kanagawa Prefecture, 1015 Kamedotachu, Fujitsu Limited (72) Inventor, Nagaaki Koshino 1015, Kamedotachu, Nakahara-ku, Kawasaki, Kanagawa Prefecture (56) Reference JP 61-155295 (JP, A) JP 64-17870 (JP, A) JP 62-27039 (JP, B2)

Claims (1)

[Claims] 1. A gas is introduced between an anode and a cathode to apply a DC voltage to cause arc discharge, and the generated plasma is ejected from a nozzle as a plasma jet,
A method for synthesizing a diamond film using direct current arc discharge plasma, which forms a diamond film by irradiating it on a substrate, wherein a carbon source is decomposed or evaporated in plasma generated by direct current arc discharge to deposit a diamond film on the substrate. A method for synthesizing a diamond film, characterized in that solid fine particles selected from diamond, platinum or palladium are continuously or intermittently sprayed in the discharge part, in plasma, or on the substrate during the process.