JPH08325095A - Method for growing diamond film and device therefor - Google Patents

Abstract

PURPOSE: To improve the homogeneity and thickness distribution of a diamond film by forming the thin film while adjusting the opening of an anode. CONSTITUTION: Plural throttle blades 15 each having a rotating shaft 16 at its center are combined to form a variable-throttle anode. The anode is set in the opening of a plasma torch 4 furnished in a reaction chamber 1. A substrate to be treated is placed on a substrate holder, a raw gas contg. hydrocarbons and hydrogen is supplied into the reaction chamber 1 through the torch 4, and an evacuating system is operated to evacuate the reaction chamber. An arc discharge is then generated between the anode consisting of the throttle blades 15 and a cathode to form a plasma jet. The rotating shaft 16 is simultaneously rotated through a motor 18 set on the torch 4 to adjust the opening diameter of the throttle blades 15, and the substrate is irradiated with carbon plasma to grow a diamond film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for synthesizing a diamond film by vapor phase synthesis. Diamond is an allotrope of carbon (C), exhibits a so-called diamond structure, has a large Vickers hardness of 10,000 Kg / mm ^2, and has a thermal conductivity of 2000 W / mk, which is far superior to other materials. In addition, the sound velocity propagating through the bulk is 18,000 m / s, which is much faster than other materials.

Therefore, various applications have been studied by utilizing this property. Among them, it is considered to be used as a constituent material of a heat sink of a semiconductor device by utilizing its high thermal conductivity. Has been.

Further, the use of abrasion resistant coating on tools, use as a diaphragm of a speaker, use as a transparent coating of optical parts, and the like are being studied.

[0004]

2. Description of the Related Art As a vapor phase synthesis method for diamond, many methods such as a microwave plasma vapor phase growth method (abbreviated microwave plasma CVD method), a hot filament method, and a combustion flame method have been put into practical use. The diamond film can be grown in the form of microcrystals on the substrate to be processed also by the above method.

The DC plasma jet CVD method (Japanese Patent Laid-Open No. 64-33096) developed by the inventors of the present invention uses hydrogen (H ₂ ) and hydrocarbon such as methane (CH ₂ ) from between the anode and the cathode.
₄ ) is supplied to the reaction chamber with the mixed gas and the exhaust system is operated to generate arc discharge between the anode and the cathode in a state where the pressure inside the reaction chamber is reduced, and the mixed gas is decomposed into plasma, This is a method in which a plasma jet containing carbon plasma collides with a substrate to be processed and a diamond film made of fine crystals grows.

In the case of using vapor-phase synthetic diamond for the above-mentioned applications, it is important that the diamond synthesis rate is high in order to reduce the manufacturing cost.
In this respect, the DC plasma jet CVD method is 100 μm / h
It can be said to be an excellent method because the above high film forming rate is obtained.

However, since this method uses direct-current arc discharge, there is a problem that the discharge sites of the anode and the cathode are heated and consumed, and the distance between the electrodes increases in proportion to the continuous discharge. is there.

[0008]

[Problems to be Solved by the Invention] D developed by the inventors
The C plasma jet CVD method is an excellent method because the diamond film formation rate is as high as 100 μm / h or more.

FIG. 3 shows the structure of a DC plasma jet CVD apparatus, in which a water cooling mechanism is provided in the reaction chamber 1.
There is a rotatable substrate holder 2 on which a substrate 3 to be processed for growing a diamond film is placed, while a plasma torch 4 is provided in the reaction chamber 1 facing the substrate 3 to be processed. There is. Here, the outer periphery of the plasma torch 4 is made of a heat-resistant insulator such as boron nitride (BN), and the cathode 5 made of tungsten (W) or water-cooled copper (Cu) is provided at the center thereof. Further, an anode 6 made of W or the like is provided at the tip end thereof, and each is circuit-connected to a DC power supply 7.

On the other hand, the plasma torch 4 contains hydrocarbon gas.
For example, methane (CH_Four) And hydrogen (H ₂) And other source gases
8 is provided with a gas pipe 9 for supplying 8
Passes through the plasma torch 4 and from the tip of the anode 6.
It is formed so as to squirt. And the exhaust of the reaction chamber 1
Anode 6 while exhausting air from the port 11 to reduce the pressure in the room
A voltage is applied between the cathode and the cathode 5 to perform arc discharge.
When the raw material gas 8 is ignited, the raw material gas 8 is about 5000 ° C.
The hydrocarbon gas is turned into plasma and heated to the anode.
Plasma jet 12 is ejected from this plasma jet
12 hits the substrate 3 to be processed and is composed of fine crystals on it.
The diamond film 13 grows.

However, the problem with this method is that it is a plasma jet.
The temperature of 12 is as high as about 5000 ° C. Therefore, the discharge electrode provided on the plasma torch 4 as the discharge continues,
Particularly, the anode 6 is consumed, the opening is expanded, and the discharge state changes with time. That is, when discharging is performed by the constant current method, the discharge voltage changes and gradually increases.

Further, since the discharge is not uniformly performed between the anode and the cathode but selectively at a specific position, the diamond film is not uniformly grown, and the plasma torch It is difficult to obtain a uniform film thickness distribution, because the growth rate is large immediately below and decreases toward the outside.

[0013]

The above-mentioned problems are characterized in that when the diamond film is synthesized on the substrate by the DC plasma jet CVD method, the size of the opening of the anode is adjustable. Can be solved by manufacturing.

[0014]

The present invention solves the problem by making the aperture of the anode a variable aperture type. FIG. 1 is a partial sectional view of a DC plasma jet CVD apparatus to which the present invention is applied.
FIG. 2 shows a plan view of the variable diaphragm type anode.

That is, the aperture diameter is adjusted by using a plurality of diaphragm blades for the anode, similar to the diaphragm of a camera. The difference is that the diaphragm blades are rotated by a motor, but at this time, they are independent of each other. That is, the blade is made of W, which has excellent heat resistance, and mechanical strength is imparted. That is, in FIG. 2, an anode is formed by three diaphragm blades 15, and a rotary shaft 16 is provided at the center of the blade 15, and the opening diameter of the anode is adjusted by the rotation of the rotary shaft 16. When the three diaphragm blades 15 are in the state shown in FIG. 7B, the aperture diameter is used as a standard. In FIG. 7A, the size of the aperture is increased, and in FIG. The state of the diaphragm blades when it is made small is shown.
That is, as shown in FIG. 1, the rotating shaft 16 is rotated by the motor 18 mounted on the plasma torch 4, thereby adjusting the size of the opening of the anode.

Next, the problem in growing a diamond film by using a DC plasma jet CVD apparatus is that the discharge between the anode and the cathode does not occur uniformly but at a specific position, and therefore the plasma jet Means that the diamond film grows thick on the substrate to be processed on the extension line because it tilts in the discharge direction.

As a countermeasure against this, it is sufficient to change the direction of the plasma jet, and this can be achieved by widening only one direction of the variable diaphragm type anode. This makes only one motor work to increase the aperture diameter. It can be realized by expanding.

When a diamond film is to be grown on the substrate to be processed, it is desired to form it with a uniform thickness over a wide area. However, in the case of the DC plasma jet CVD method, the central part on which the jet hits has a large film thickness. , The phenomenon of becoming thinner as going to the surroundings is inevitable. Therefore, as a method for forming a uniform film, the diaphragm direction of the variable diaphragm type anode is periodically changed and the plasma jet is irradiated so as to draw a circle on the substrate to be processed. The thickness can be equal.

Next, since the reaction gas hits the diaphragm blade according to the present invention, mechanical strength is required in addition to heat resistance.
It is preferable that each of the three sets of diaphragm blades is formed by a plurality of sheets, which increases strength and prevents deformation.

[0020]

【Example】

Example 1 (Related to FIG. 2) A variable diaphragm type anode composed of three pairs of diaphragm blades has a thickness of 1
Five W plates each having a thickness of mm were formed in combination, and each diaphragm blade could be adjusted in six stages by three stepping motors provided on the plasma torch.

Further, the voltage value between the anode and the cathode is input to the control personal computer, and when the voltage value exceeds the set value, the stepping motor operates and the diaphragm blades move to reduce the opening diameter, thereby reducing the opening diameter. It was kept constant and the voltage value was kept constant. Conventional plasma jet CVD
In the device, about 10 mm of wear is observed after 10 hours of discharge.

First, as a substrate to be processed, an M of 20 × 20 × 5 mm
o Use a plate and place it on the water-cooled substrate holder,
As a raw material gas, H ₂ is supplied at a flow rate of 40 liters / minute, Ar is supplied at a rate of 20 liters / minute, and CH ₄ is supplied at a flow rate of 1 cc / minute into the reaction chamber through the plasma torch. Decompress the chamber to 20 torr,
Arc discharge is performed with a current of 20 A from a DC power source, the aperture diameter of the diaphragm blade of the anode is adjusted to a discharge voltage of 150 V, and a plasma jet is irradiated to form a film at a deposition rate of 250 μm /
A diamond film was grown at h.

As a result, it was possible to irradiate the plasma jet in a stable state of 20 A and 150 V, and to obtain a uniform diamond film. Example 2 A diamond film was grown on a substrate to be processed in exactly the same manner as in Example 1. At this time, a diamond film was grown by a control personal computer.
Each of the stepping motors was rotated in turn, and the irradiation direction of the plasma jet was changed by making the opening of the anode elliptical so that the substrate to be processed was irradiated so as to draw a circle. As a result, a flat diamond film having a better film thickness distribution than in Example 1 could be obtained.

[0024]

EFFECTS OF THE INVENTION A variable diaphragm type anode is used to compensate for fluctuations in the output of the plasma jet due to exhaustion of the anode, and by carrying out the present invention in which the irradiation direction of the plasma jet is controlled, it is possible to achieve uniformity in the growth of diamond film. In addition, the film thickness distribution can be improved.

[Brief description of drawings]

FIG. 1 is a DC plasma jet CVD according to the present invention.
It is a fragmentary sectional view of an apparatus.

FIG. 2 is a plan view showing the operation of the variable diaphragm type anode.

FIG. 3 is a sectional view showing the configuration of a DC plasma jet CVD apparatus.

[Explanation of symbols]

 1 Reaction Chamber 3 Processed Substrate 4 Plasma Torch 5 Cathode 6 Anode 8 Material Gas 12 Plasma Jet 13 Diamond Film 15 Diaphragm Blade 16 Rotating Shaft 18 Motor

Claims (3)

[Claims] 1. A plasma torch having a cathode and an anode is supplied with a raw material gas containing hydrocarbon and hydrogen to be jetted into a reaction chamber, and the exhaust system is used to reduce the pressure in the reaction chamber to form the anode and the cathode. A diamond consisting of microcrystals is formed on the substrate by a DC plasma jet CVD method in which an arc discharge is generated between them to form a plasma jet containing carbon plasma, and the carbon plasma is applied to a substrate to be processed placed in a reaction chamber. A method for growing a film, wherein the film is formed while adjusting the opening of the anode. 2. An apparatus for growing a diamond film, wherein the anode opening of the plasma torch is a variable aperture type anode. 3. The method for growing a diamond film according to claim 1, wherein the diaphragm shape of the variable diaphragm type anode is changed to adjust the film thickness distribution of the diamond film.