JPH04136179A - Microwave plasma cvd device - Google Patents

Abstract

PURPOSE:To prevent the contamination and damage of a microwave introducing window and antenna by plasma and to allow the stable use over a long period of time by using a coaxial cable to introduce microwaves into the reaction chamber of the microwave plasma CVD device and connecting the conductor of the coaxial cable and a base body. CONSTITUTION:The microwaves emitted from a microwave power source 1 propagates in a waveguide 2 and arrive at a mode converter 3 where the microwaves are converted to a TEM mode suitable for the coaxial cable and propagate in the coaxial cable 4, by which the microwaves are introduced into the reaction chamber 8 and are introduced through the antenna 10 into the reaction chamber 8. The plasma 12 is generated only around the periphery of the base body in this way. The microwave introducing window plasma CVD device of this invention introduces the microwave directly into the substrate by using the coaxial cable in such a manner and, therefore, the problems, such as contamination and damage of the microwave introducing window and antenna, do not arise. Thus the device is usable stably over a long period of time. Since the plasma is stabilized, the quality of the film is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a microwave plasma CVD apparatus, and in particular,
The present invention relates to a microwave plasma CVD apparatus that can stably form a film on a base (substrate) of any shape for a long period of time.

[Prior art] Plasma processes using microwaves are non-polar discharges and have very simple equipment, so in recent years CV
D (Chenical Vapor Deposit
It has come to be widely applied to the formation of various thin films by the ion method.

Among these, it is industrially practiced to form a film of tire cent or amorphous silicon using a microwave plasma CVD system. With the practical use of this microwave plasma CVD apparatus, there is a desire to develop an apparatus that can stably form films over a long period of time.

As shown in FIG. 4, a conventional microwave plasma CVD apparatus introduces microwaves 13 generated by a microwave power source 1 into a reaction chamber 8 through a waveguide 2 and a microwave introduction window 14 made of quartz. A plasma 12 was generated to form a film on the substrate 11.

[Problem to be solved by the invention] However, the above-mentioned conventional microwave plasma CV
In the D device, firstly, the plasma 12 is generated locally around the microwave introduction window 14, so the microwave introduction window 14 may be contaminated or damaged due to heating by the plasma. There is a problem. Such contamination or damage to the microwave introduction window posed a problem because it made the plasma unstable and the microwave introduction efficiency was inconsistent.

Therefore, the following device has been proposed as a device for removing dirt from the microwave introduction window.

■Unexamined Japanese Patent Publication No. 63-117992 discloses that a rigid coil is arranged in a reaction chamber so as to surround a substrate, and microwaves are transmitted to the rigid coil via a coaxial cable to control the plasma generation area and react. A technique has been disclosed to prevent problems caused by heating of indoor walls.

However, this technique has the problem that the rigidano coil comes into contact with the plasma and becomes contaminated, reducing the microwave introduction efficiency and making the plasma unstable.

■In addition, Japanese Patent Application Laid-Open No. 1-92374 discloses that the waveguide has a coaxial structure, the inner conductor and the outer conductor of the coaxial line are short-circuited in a vacuum container, and microwaves are introduced by the action of a magnetic field. , a technique has been disclosed for preventing a decrease in microwave introduction efficiency due to contamination of the microwave introduction part.

■Furthermore, Japanese Patent Application Laid-Open No. 376911 discloses that when microwaves are guided through a coaxial waveguide to a vacuum vessel, the inner conductor of the coaxial waveguide is made into a linear antenna or a spiral coil. , a technique for supplying microwaves to the inside of a plasma reaction chamber has been disclosed.

However, JP-A-1-92374 and JP-A-2
The technology described in No. 37698 generates plasma at the end of the coaxial cable and places the board at a remote location, which can lead to contamination of the antenna and coil.
There is a problem in that it is difficult to generate stable plasma on the substrate.

Second, in conventional microwave plasma CVD apparatuses, the discharge area is limited by the size (tube diameter) of the waveguide, making it difficult to increase the area. For example, when a reaction chamber is installed inside a waveguide, there is a limit to the size of the waveguide, which limits the size of the reaction chamber and the size of the substrate etc. installed in the reaction chamber. It was not possible to form a film on a large base surface.

Third, electron cyclotron resonance (ECR) plasma C
In VD devices, in order to avoid contact between the microwave introduction window and the plasma, a strong external magnetic field must be applied, resulting in a problem that the device becomes larger, more complicated, and more expensive.

The present invention has been made in view of the above-mentioned problems.
Microwave plasma CVD equipment that prevents plasma contamination and damage to the microwave introduction window and antenna, allows stable use over a long period of time, and can process substrates of any size and shape. For the purpose of providing.

[Means for Solving the Problems] In order to achieve the above object, the microwave plasma CVD apparatus of the present invention uses microwaves as an excitation source to decompose a source gas into a plasma state and deposit a thin film on a substrate. In the apparatus, microwaves are introduced into the reaction chamber through a coaxial cable, and the conductor of the coaxial cable is connected to the base.

Hereinafter, the present invention will be specifically described with reference to the drawings.

FIG. 1 is a sectional view showing a microwave plasma CVD apparatus according to a specific example of the present invention.

In the figure, l denotes a microwave power source (magnetron oscillator), which oscillates microwaves at a predetermined frequency.

Reference numeral 2 denotes a waveguide, which is a transmission line made of hollow metal, through which the microwave generated by the microwave power source 1 propagates.

A moat converter 3 converts the microwave propagated within the waveguide 2 into a coaxial line moat.

4 is a coaxial cable (coaxial line), and a mode converter 3 converts the microwave into a mode. The coaxial cable 4 includes an inner conductor 4a, an outer conductor 4b, and an inner insulator 4.
It is composed of c. Here, a material such as copper, stainless steel, or aluminum is used as the inner conductor 4a of the coaxial cable, and a material such as copper, stainless steel, or aluminum is used as the outer conductor 4b.

5 is a reaction vessel, which is made of stainless steel (SO3, etc.), aluminum (A1, etc.).

A water-cooled vibrotube is provided around the outer circumferential surface of the reaction vessel 5 in order to prevent overheating of the apparatus.

7 is a Pel jar installed in the reaction vessel, which contains quartz,
It is made of materials such as stainless steel. The inside of the Pelger 7 is a reaction chamber 8, and a coaxial cable 4 is inserted into the reaction chamber 8. The coaxial cable insertion portion 9 in the Pelger 7 is vacuum sealed.

IO is an antenna provided at the tip of the internal conductor 4a of the coaxial cable 4, and the tip of the antenna IO is the base (substrate).
It is connected to 11.

Since the antenna 1O is exposed to plasma, it is made of a metal with good thermal conductivity (for example, Cu) or a metal with a high melting point (for example, W, Ta, etc.).

Also, to avoid overheating, the interior can be double-walled and water-cooled.

It is preferable to adjust the length of the antenna lO appropriately in order to match the microwave and efficiently propagate the microwave to the substrate.
The length of the connection between the antenna IO and the base (substrate) 11 is preferably mechanical as long as the connection is in mechanical contact. It is preferable to adjust it to

The base (substrate) 11 is made of molyfdenum (Mo).

Conductive materials such as tungsten (W), cemented carbide (IC-CO), or silicon (Si), germanium (G)
e).

Preferably, the material becomes conductive when heated, such as various types of ceramic rough. The shape of the base body 11 is not particularly limited, and may have a special shape such as a cutting tip or a trill blade.

Next, the operation of the microwave plasma CVD apparatus having the above configuration will be explained.

Microwaves emitted from a microwave power source 1 propagate through a waveguide 2 and reach a moat converter 3, where they are converted into a TEM moat suitable for coaxial cables. The mote-converted microwave propagates through the coaxial cable 4, is guided into the reaction chamber 8, and is introduced into the substrate 11 through the antenna IO. As a result, plasma 12 is generated only around the base.

As described above, since the microwave plasma CVD apparatus of the present invention directly introduces microwaves into the substrate using a coaxial cable, problems such as contamination or damage to the microwave introduction window, antenna, etc. do not occur. Therefore, it can be used stably for a long period of time.

In addition, 1. Since the plasma is stable, various adjustments such as re-adjustment of matching of the microwave circuit to keep the plasma constant can be reduced, and the quality of the film can be improved.

In the microwave plasma CVD apparatus of the present invention, the shape of the antenna is not limited to a linear shape, but can be modified as appropriate depending on the size, shape, etc. of the substrate.

For example, as shown in FIGS. 2(a) to 2(d), a coil shape (spiral shape) (FIG. 2(a)), a conical coil shape (FIG. 2(B)), a link shape (FIG. 2(C)) ), box-shaped (
The image is transformed into (d) in the same figure. Even if such a modified antenna is used, if a substrate support of a shape suitable for each antenna shape is attached and the substrate is placed on it, a flat surface can be obtained. It is also possible to form a film on a substrate.

Further, as shown in FIG. 3, by using a plurality of coaxial cables, it is possible to easily form a film on a large area of a substrate surface or on a plurality of substrate surfaces. In addition, when using multiple coaxial cables, use the stuff tuner 1 so that the lengths of the coaxial cables may be different.
5 is preferably arranged on each coaxial cable.

[Examples] Hereinafter, the present invention will be explained in more detail based on Examples.

Using the microwave plasma CVD equipment shown in Figure 1,
A mixture of hydrogen (H2) and methane (C) (8299%, CIL 11) was added to the reaction chamber of the same device at 1005C.
CM was introduced at a flow rate, microwave output was 150 W, microwave frequency was 2.45 G) Iz, and the pressure inside the reaction chamber was 20 T.
A Tirescent thin film was coated on the surface of a 5 φ diameter carbide trill substrate by generating plasma using microwaves under the conditions of 0.05 mm.

After 30 2-hour reactions, we examined the condition of the inner wall of the Pelger and found that some light brown deposits were observed on the inner wall of the Pelger, the plasma was stable, and the quality of the obtained Diacent thin film was good. There was.

Using the microwave plasma CVD equipment shown in Figure 4,
Coach ink was applied using a tire cent thin film in the same manner as in the above example except that the microwave output was set to 200 ml.

After conducting the reaction for 2 hours 30 times, the condition of the inner wall of the Pelger was examined, and it was found that black soot had adhered to the inner wall of the Pelger, and the state of the plasma was also unstable. Pelger was also seen glowing due to overheating caused by the plasma.

[Effects of the Invention] As explained above, the microwave plasma CV of the present invention
Device D can be used stably for a long period of time without problems such as plasma contamination or damage to the microwave introduction window or antenna.

[Brief explanation of the drawing]

FIG. 1 shows a microwave plasma C according to a specific example of the present invention.
2(a) to 2(d) are perspective views showing modified examples of the antenna, and FIG. 3 is a sectional view showing another specific example of the microwave plasma CVD apparatus. FIG. 4 is a sectional view showing a conventional microwave plasma CVD apparatus. 1 Microwave power source 2 Waveguide 3/Moat converter 4. Coaxial cable 8 Reaction chamber IO antenna 11 Substrate (substrate) 12 Plasma Fig. 3 Fig. 4

Claims (1)

[Claims] Microwave plasma C that uses microwaves as an excitation source to decompose a source gas into a plasma state and deposit a thin film on a substrate.
A microwave plasma CVD apparatus characterized in that the microwave is introduced into a reaction chamber through a coaxial cable, and the conductor of the coaxial cable is connected to a base.