JPH062946B2 - Method for forming silicon carbide thin film - Google Patents

Description

The present invention relates to a silicon carbide (SiC) thin film forming member used in, for example, a jig for high temperature using a CVD method for carbon or carbide base material, or ceramics. And a method of forming on a metal or alloy material having relatively high heat resistance.

(Prior Art) As a method for forming a carbide film, a vapor phase reaction, that is, a CVD method is known. The CVD method is a method in which a constituent element of a film is made into a compound that easily vaporizes, this is introduced into a reaction system by a carrier gas, and a solid layer generated by a chemical reaction of the introduced raw material gas is deposited on a substrate to form a film. Is. Further, when a silicon carbide thin film is formed on carbon (graphite) or a carbide base material by this CVD method, conventionally, the inside of the reaction furnace is replaced with nitrogen gas and exhausted, and then, between the rod-shaped graphite base material and the electrode. Glow discharge by alternating current
A silicon carbide thin film is formed by electrically heating to 1400 ° C. and supplying an organosilicon gas such as tetramethylsilane at a constant flow rate (for example, 2.8 × 10 ⁻⁴ mol / min) into the glow discharge plasma.

According to this conventional method, since the base material has to be heated to about 1400 ° C., there is a problem that deformation or film peeling easily occurs due to the difference in thermal expansion between the base material and the silicon carbide thin film.

(Problems to be Solved by the Invention) In view of the above-mentioned drawbacks of the prior art, the present invention can maintain the heating temperature of the base material at a relatively low temperature, which may cause deformation of the thin film or peeling from the base material. It is intended to provide a method for forming a thin film.

(Means for Solving the Problems) In order to achieve this object, the method for forming a silicon carbide thin film of the present invention is to install a base material in a reaction furnace, locally heat the base material, The chemical formula Si (C
H ₃ ) _x Cl _y H _z (provided that x + y + z = 4, x ≠ 0) is supplied, and the heating point is moved to perform CVD by decomposition or condensation reaction of the organosilicon compound.
A silicon carbide thin film is formed on the moving portion of the heating point by a method.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG. A table 3 is installed in the reaction furnace 1 which is replaced by an argon gas as a carrier gas so that the position can be controlled in the X and Y directions by a numerical controller 2, and a base material 4 is placed on the table 3.
While moving the substrate 4 by the numerical controller 2, the laser beam 6 is locally irradiated onto the substrate 4 through the potassium chloride window 5, whereby the temperature of the substrate surface portion at the laser beam irradiation point is locally irradiated. By adjusting the laser output, the temperature is adjusted to 1250 to 1350 ° C., the average temperature of the base material 4 and the temperature inside the reaction furnace 1 are set to about several hundred degrees. At the same time, the mixed gas 15 of the raw material gas and the carrier gas is ejected from the nozzle 14 attached to the reaction furnace 1 toward the same point as the irradiation point of the laser beam 6 on the base material 4, and the silicon carbide thin film is locally formed. To form.

The device for irradiating the laser beam 6 is a carbon dioxide laser 7, a 99% transmission mirror 8 provided on the output side thereof,
It comprises a laser power meter 9 for controlling a laser power source 10 by detecting a part of the reflected beam from the transmission mirror 8, a ZnSe lens 11 for guiding the laser beam, and a total reflection mirror 12. Reference numeral 13 is an internal confirmation window provided in the reaction furnace 1, and reference numeral 42 is a gas outlet in the reaction furnace 1.

The supply system of the mixed gas 15 is configured as follows. Reference numeral 16 is a carrier gas pressure vessel, and its supply pipe line 17 has manual valves 18 and 18 'for adjusting the flow rate.
A cock 19 to 21, a deoxidizer 22, a dehydrator 23, a pressure gauge 24 to 26, an oxygen analyzer 27, and a flow meter 28. On the other hand, the source gas supply system is
A raw material container 29 containing organic silicon, and a pump 3 for feeding the raw material from the container 29 to a vaporization chamber 30 which is a heat insulating container.
1, a conduit 32 having a heat insulating layer that joins the vaporized organosilicon gas from the vaporization chamber 30 to the carrier gas supply conduit 17, and the raw material container 29 and the vaporization chamber 30 are filled with the carrier gas. It consists of bypass conduits 33 to 35, a manual valve 36 provided in these conduits, a flow meter 37, cocks 38 and 39, and traps 40 and 41.

The formation rate of the silicon carbide thin film varies depending on the laser beam diameter, laser beam output, carrier gas flow rate, type of organic silicon gas, flow rate and material of the base material, and moving speed. min,
Dimethyldichlorosilane ((CH ₃ ) ₂ SiC
l ₂ ) and its flow rate is 2.8 × 10 ⁻³ mol / min, nozzle 1
The inner diameter of 4 is 0.2 mm, the output of the laser beam 6 is 200 W, the diameter of the laser beam 6 is 0.2 mm, the rod-shaped graphite with a diameter of 50 mm is used as the base material 4, the moving speed is 1 mm / sec, and the temperature of the laser beam irradiation point of the base material is 4. Is 1250 ~ 1350 ℃, when the thin film is formed so that the furnace temperature is 300 ℃, 0.2 mm width, thickness
A silicon carbide thin film having a Vickers hardness of Hv3000 was formed at 0.1 μm. Further, a high adhesion strength of 10 kg / mm ² was obtained as compared with the adhesion strength of 6 kg / mm ^{2 of} silicon carbide formed by the conventional method.

The reason why such high adhesion strength is obtained is considered as follows. That is, when the temperature of the base material 4 is uniformly set to 1400 ° C. to form a film as in the conventional method, as shown in FIG. The difference ΔX in the total amount of shrinkage increases with the cooling of No. 2, but in the case of locally forming a film, FIG.
It is considered that the difference ΔX ′ in the shrinkage amount is small, and therefore the adhesion strength is high, so that the deformation and peeling hardly occur. In the present invention, locally forming a thin film does not mean that a thin film is locally formed as a product, but means that a thin film is transiently locally formed at the stage of formation. As a product, a thin film may be formed on the whole.

The laser beam diameter, the laser beam output, the carrier gas flow rate, the organosilicon gas flow rate concentration, and the moving speed of the substrate are factors that are mutually related in forming a thin film, but a generally preferable range is a carbon dioxide laser. Is a laser beam diameter of 0.1 to 2 mm, laser beam output of 100 to 200 W,
The flow rate of argon gas is 0.5 to 2 / min, and the flow rate of organic silicon gas is 0.001 to 0.0 in the case of dimethyldichlorosilane.
When the thin film is formed at 03 mol / min and the inner diameter of the nozzle is 0.1 to 0.3 mm, the moving speed is 1 to 10 mm / sec.

The raw material gas has a chemical formula of Si (CH ₃ ) _x Cl _y.
An organic silicon compound of H _z (however, x + y + z = 4, x ≠ 0) is used, but hydrogen is used to promote decomposition during the self-decomposition of the source gas or to prevent impurities such as silicon and carbon from being deposited. Hydrocarbons (methane, benzene) etc. are mixed as a carrier gas.

FIG. 3 shows another embodiment of the present invention, in which the plasma torch 43 to the plasma beam 4 are used instead of the laser beam.
4 is irradiated onto the graphite base material 4, and the raw material contained in the raw material container 29 is jetted as a liquid from the nozzle 14 by the pump 31 to the irradiation point. In order to prevent oxidation, argon gas or the like is made to flow in through the inlet 45, and the raw material is vaporized at the moment when it is jetted onto the base material 4 to cause a thin film forming reaction. Also in this embodiment, the average temperature of the substrate 4 or the temperature in the reaction furnace 1 can be kept low. When this plasma beam is used, the beam diameter is 10 mm, the beam output is 2 kW, the argon gas flow rate is 1 / min, the dimethyldichlorosilane flow rate is 1 mol / min, and the substrate moving speed is 1
When a thin film was formed by moving a round bar having a diameter of 50 mm in mm / sec, a silicon carbide thin film having a Vickers hardness of Hv3000 and an adhesion strength of 9 kg / mm ² was formed with a width of 10 mm and a thickness of 0.1 μm.

When a liquid is used as a raw material in this manner, the raw material supply rate can be increased, which has the advantage that the thin film formation area per unit time can be increased. This liquid is used in the embodiment shown in FIG. Can also be done at. Further, a microwave can be used instead of the plasma beam or the laser beam.

FIG. 4 shows another embodiment of the present invention, which is a high-voltage power supply device 46.
One pole of the output of is connected to the base material 4 directly or via the table 3, and the other pole is connected to the sharp electrode 47 facing the base material 4 to locally generate arc discharge. The thin film is locally formed. In addition,
In this embodiment, the arc discharge may be alternating current or direct current, and high frequency may be used.

As an example of using such a discharge arc, an output voltage in which the substrate 4 is a cathode and the electrode 47 is an anode having a diameter of 1 mm
Using a 30V DC power supply device 46, the distance between the electrode 47 and the base material 4 was 5 mm, the flow rate of the organic silicon gas (dimethyldichlorosilane) was 0.001 mol / min, and the moving speed of the base material was 0.2 mm /
If a thin film is formed by moving a round bar with a diameter of 50 mm as sec, Vickers hardness H with a width of 1 mm and a thickness of 0.1 μm
A silicon carbide thin film with v3000 and an adhesion strength of 9 kg / mm ² was formed.

In the case of carrying out the present invention, in addition to the laser beam, the plasma beam, the microwave, and the discharge arc, a glow discharge is made to act in the vicinity of the base material, whereby the thinning of the raw material is promoted. That is, organic silicon decomposes and condenses to form a silicon carbide thin film, but when the supply amount increases, decomposition and condensation cannot be completed in time, and in the case of having a methyl group, elimination of the methyl group becomes incomplete. For this reason, the methyl groups trapped between the silicon carbide particles eventually become free carbon and precipitate between the silicon carbide particles. In order to prevent the precipitation of free carbon, the decomposition and condensation should be promoted. When glow discharge is applied, decomposition and condensation reactions of organic silicon are promoted, precipitation of free carbon is prevented, and a thin film having high hardness is formed. Further, as the shape of the material for forming the thin film according to the present invention, in addition to the round bar, any shape such as a plate shape or a ring shape can be selected.

(Effects of the Invention) As described above, according to the present invention, by locally forming a thin film, it is possible to form a silicon carbide thin film that is unlikely to peel or deform. Although the present invention refers to a method of forming a silicon carbide thin film, for example, when a base material such as graphite is stacked and the base material is stacked and bonded to form a film, only a film is formed on the surface. Instead, it penetrates into the bonding gap to form a silicon carbide film on the opposing bonding surfaces, and finally both base materials are strongly bonded by the formed silicon carbide. Therefore, the present invention is useful as a bonding method by silicon carbide. It is something.

[Brief description of drawings]

FIG. 1 is an apparatus configuration diagram for explaining an embodiment of the method of the present invention, FIG. 2 is an explanatory diagram of the principle of the present invention, and FIGS. 3 and 4 are apparatus configuration showing other embodiments of the present invention. It is a figure.

Claims (1)

[Claims] 1. A base material is installed in a reaction furnace, the base material is locally heated, and chemical formula Si (C) is introduced from a nozzle toward the heating point.
H ₃ ) _x Cl _y H _z (provided that x + y + z = 4, x ≠ 0) is supplied, and the heating point is moved to perform CVD by decomposition or condensation reaction of the organosilicon compound.
A method for forming a silicon carbide thin film, which comprises forming a silicon carbide thin film on a moving portion of the heating point by a method.