JPH07310186A - Plasma cvd method and apparatus therefor - Google Patents

Abstract

PURPOSE:To form films having excellent denseness and tight adhesion at a high film forming rate on substrates by forming the plasma formed by an arc discharge to a sheet form, introducing this plasma into a film forming chamber and impressing a magnetic field thereon, thereby bending the plasma. CONSTITUTION:The discharge gas introduced from a gas introducing port 20 is converted to the plasma by the arc discharge of a plasma forming means 1 and the formed plasma is introduced into a plasma introducing section 2. The plasma advance to a pressure regulating chamber 5 in the state that the plasma is converged to a circular cylindrical shape by the magnetic field formed by a permanent magnet built in a first intermediate electrode 21 and an air-core coil 4 built in a second intermediate electrode 22. The plasma is deformed to the sheet-like plasma 15 by a first magnetic field impressing means 3 during the course thereof and is accelerated by a voltage applying means 14, by which the plasma is introduced into the pressure regulating chamber 5. Further, the twist of the plasma is corrected by a second magnetic field impressing means and is introduced into the film forming chamber 6. At this time, the sheet-like plasma 15 is bent nearly 90 deg. by a third magnetic field impressing means 7 and is converted to an anode 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD method, which is a kind of thin film forming method, and an apparatus used therefor.

[0002]

2. Description of the Related Art Thin film forming methods are roughly classified into physical methods (P
There are two types: VD) and chemical method (CVD). Typical examples of the former are sputtering and vacuum evaporation. The CVD method is classified into the following three types according to the means for giving the activation energy necessary for causing a chemical reaction. The method of using heat (increasing the temperature) is thermal CVD, light (from near ultraviolet to vacuum ultraviolet light,
A method using laser light) is called optical CVD, and a method using plasma is called plasma CVD. The plasma CVD method includes a method using thermal plasma and a method using low temperature plasma, but industrially, low temperature plasma generated by glow discharge or the like is often used. Conventional plasma CV
As the plasma source of the D device, glow discharge or microwave discharge generated by direct current or high frequency has been used, but all of them have low plasma density (10 ⁸ to 10 ¹² ions) because they use glow discharge. / cm ³ ) and, as a result,
There is a problem that the film forming speed is slow.

A film formed by the CVD method is often used as an insulating film or a conductive film, but a dense film cannot be obtained and the adhesion is often poor. Further, in the plasma CVD method, since the reactive species that contribute to film formation are ions and neutral particles, there is a problem in that the electrical characteristics (insulation and conductivity) of the obtained film are not high.

[0004]

On the other hand, the plasma density obtained by the arc discharge type composite cathode type plasma gun is 10 ¹² to 10 ¹⁴ ions / cm ³ , and by using this in the plasma CVD apparatus. High-speed film formation can be expected (Vacuum Volume 25, No. 10 (1982)). Therefore, it has been considered to use arc discharge as a plasma source to obtain a higher plasma density (JP-A-60-110876, JP-A-1-52781). However, in these methods, since the substrate is located in the plasma, the substrates that can be used are limited due to ion bombardment to the substrate. Further, when a metal compound is formed into a film, for example, when a metal compound gas is introduced from a hole provided in an anode, the hole is easily covered with the metal compound (Japanese Patent Laid-Open No. 1-25278).
1).

Therefore, it has been carried out that the position of the substrate is placed outside the plasma and the reaction gas introduction part is placed at a position different from the anode (Japanese Patent Laid-Open No. 3-215671). However, if the substrate position is taken out of the plasma without changing the plasma density,
Ions and neutral active species reaching the substrate are drastically reduced, film formation speed,
There is a problem that the use efficiency of the reaction gas is significantly reduced. Further, since the film forming speed is increased, when the film is formed at a low degree of vacuum, the plasma becomes unstable and it is difficult to manufacture a stable and uniform film.

The present invention aims to solve such a problem.

[0007]

To achieve the above object, in the present invention, firstly, a first step of generating plasma by arc discharge, a second step of shaping the plasma into a sheet by a magnetic field, and the sheet. Plasma comprising a third step of bending a sheet-shaped plasma by a magnetic field, and a fourth step of forming a thin film by a gas phase reaction on a substrate placed in the traveling direction of the plasma before the sheet-shaped plasma is bent. A CVD method (claim 1) is provided.

Secondly, plasma generating means for generating plasma by arc discharge, magnetic field applying means for deforming the shape of the plasma into a sheet shape, supporting means for supporting the substrate, the sheet from the side facing the substrate. Gas supply means for supplying a reaction gas through a sheet-shaped plasma, magnetic field application means for bending the sheet-shaped plasma, a film forming chamber for holding the substrate at a predetermined pressure, and a film forming chamber having a predetermined film forming chamber. Provided is a plasma CVD apparatus (Claim 2) comprising exhaust means for setting the pressure.

Thirdly, a first step of generating plasma by arc discharge, a second step of shaping the plasma into a sheet by a magnetic field, a third step of accelerating electrons in the sheet of plasma, the sheet of Plasma CVD, which comprises a fourth step of bending the plasma in a magnetic field by a magnetic field, and a fifth step of forming a thin film by a gas phase reaction on a substrate placed in the traveling direction of the plasma before bending the sheet-shaped plasma. Providing a law (claim 3).

Fourth, plasma generating means for generating plasma by arc discharge, magnetic field applying means for deforming the shape of the plasma into a sheet shape, voltage applying means for accelerating electrons in the sheet-like plasma. A supporting means for supporting the substrate, a film forming chamber for holding the substrate at a predetermined pressure, a pressure adjusting chamber installed between the plasma generating means and the film forming chamber, the pressure adjusting chamber and the film forming Exhaust means for setting each chamber to a predetermined pressure, gas supply means for supplying a reaction gas from the side facing the substrate via plasma in the film forming chamber, and for bending the direction of plasma in the film forming chamber There is provided a plasma CVD apparatus (claim 4) constituted by the magnetic field applying means.

[0011]

In the present invention, since plasma is generated by arc discharge, its density can be increased by 50 to 100 times that of plasma generated by conventional glow discharge.
Therefore, the ionization degree of the carrier gas (Ar) is as high as several tens of percent, and the ion density, electron density, and neutral active species density are all orders of magnitude higher than those of conventional plasma. Here, neutral active species such as radicals play the most important role in the thin film formation process in plasma CVD. However, direct impact of ions or electrons on the substrate during film formation is often undesirable from the viewpoint of film physical properties (particularly electrical characteristics). Therefore, it is desirable to supply only the neutral active species onto the substrate.

Here, when the sheet-like plasma introduced into the film forming chamber is bent by a magnetic field, electrons and ions are bent by the magnetic field, but neutral active species have no electric charge and therefore are not affected by the magnetic field. Go straight to. In the present invention, since the substrate is installed in the direction toward the neutral active species, the neutral active species contributes to the film formation efficiently. As a result, the electrical characteristics of the film are improved. Also, by applying a magnetic field, the shape of the plasma is formed into a sheet shape, and the uniformity of the plasma is improved, so the energy distribution of neutral active species is also highly uniform, and the uniformity of the formed thin film is It is remarkably improved as compared with CVD of (claims 1 and 2).

Further, the higher the kinetic energy of the neutral active species, the faster the film formation rate. Therefore, by increasing the energy of the electron flow in the discharge plasma, the kinetic energy of the generated neutral active species also increases, and higher speed film formation becomes possible. In order to increase the energy of the electron flow, the gas pressure in the pressure adjustment chamber is set lower than that in the film formation chamber to suppress the ionization action of electrons in the plasma flow. Next, an accelerating voltage is applied by a voltage applying means provided in front of the pressure adjusting chamber to accelerate the electrons. The accelerated electrons accelerate the ionization of the carrier gas and the reaction gas in the film forming chamber having a high pressure, and high density plasma is generated. At this time, the backflow of ions from the film formation chamber to the pressure adjustment chamber occurs, the space potential is neutralized, and the acceleration of electrons proceeds stably. By accelerating the electron flow region in the discharge plasma, the gas ionization efficiency is also increased, and the energy of neutral active species such as radicals and the ionization efficiency of the carrier gas are significantly improved, enabling high-speed film formation. . In order to further increase the film formation rate, it is preferable to form the film at a low degree of vacuum. According to the present invention, it is possible to form a uniform and stable plasma by shaping the plasma into a sheet with a magnetic field even at a low vacuum degree (about 10 ^-1 Torr) as compared with the conventional plasma CVD using a pressure gradient type plasma source. . Moreover, since the mean free path of ions is shortened at a low degree of vacuum, wraparound occurs, and film formation (step coverage) on a surface having complicated irregularities becomes easier (claims 3 and 4).

Hereinafter, the present invention will be described in more detail by way of examples with reference to the drawings, but the present invention is not limited thereto.

[0015]

【Example】

[Embodiment 1] FIG. 1 is a schematic sectional view of a plasma CVD apparatus according to an embodiment of the present invention (claims 3 and 4). This plasma CVD apparatus includes a plasma generating unit 1, a plasma introducing unit 2, an air-core coil 4 installed between the plasma generating unit 1 and the plasma introducing unit 2, a pressure adjusting chamber 5, a plasma introducing unit 2 and a pressure adjusting chamber 5. The first magnetic field applying means 3 installed between the first magnetic field applying means and the voltage applying means 14 and the acceleration power source 18, which are installed to accelerate the electrons in the plasma, the film forming chamber 6, and the twisting of the sheet-like plasma. Then, the second magnetic field applying means 3a for improving the uniformity, the third magnetic field applying means 7 for bending the plasma in a predetermined direction, and the gas supplying means 9 for uniformly supplying the reaction gas into the film forming chamber. An exhaust port 1 connected to a means 12 for supporting the substrate 11 and an exhaust means (not shown) for setting the film forming chamber to a predetermined pressure.
3b and.

The inlet and outlet of the pressure adjusting chamber 5 are set to a size that does not come into contact with the sheet-shaped plasma (hereinafter referred to as sheet-shaped plasma) 15. Further, the pressure adjusting chamber has an exhaust port 1 connected to an exhaust means (not shown).
3a is provided, and the internal pressure is reduced to 10 by this exhaust means.
Adjustable within the range of ^-3 to 10 ^-6 Torr. The third magnetic field applying means 7 applies the sheet-shaped plasma 15 to the surface by approximately 90 °.
It is provided to bend and lead onto the anode 16. The substrate 11 is installed in the plasma traveling direction before the sheet-shaped plasma 15 is bent.

In order to form a film efficiently, the film forming chamber 6 has a first chamber in which an anode 16 and a reaction gas supply means 9 are installed and a second chamber in which a substrate holder 12 for supporting a substrate 11 is installed.
The room may be divided into These chambers are partitioned by the gate valve 17. In such a configuration, when the gate valve 17 is closed and the substrate 11 is taken in and out in the second chamber, it is not necessary to return the first chamber to the atmospheric pressure, so that the film formation cycle time can be shortened. it can. An exhaust port 13c is also provided at a position corresponding to the second room, and is connected to an exhaust means (not shown). The inside of the first and second chambers is configured to be adjusted to a predetermined pressure by exhaust means.

The substrate supporting means 12 is installed so as to be movable in the arrow direction. By moving the substrate supporting means 12, the distance between the sheet-shaped plasma 15 and the substrate 11 is increased.
It can be adjusted in the range of 10 to 300 mm. This distance can also be changed depending on the film forming material and the desired film forming rate. Next, a process of forming an amorphous carbon thin film by the plasma CVD apparatus of this embodiment will be described.

First, the substrate 11 is a single crystal having a diameter of 8 inches.
Prepare a Si wafer and place this substrate 11 on the substrate holder 12.
Install. And connected to the exhaust ports 13a, 13b
The pressure in the pressure control chamber is 5 × 10^-6Tor
r, the pressure in the first chamber in the deposition chamber is 5 × 10^-6Set up in Torr
After setting, the main discharge power source 19 of the plasma generating means 1
Apply a DC voltage of about 600V between the cathode and anode 16
To do. At this time, as described above, the discharge gas is supplied from the gas inlet 20.
Gas (Ar gas) is introduced and the amount introduced is adjusted.
Maintain the pressure in the area near the cathode at around 1 Torr
It Also, installed in the first room by the exhaust means
The pressure in the region near the anode 16 is about 2 × 10 ^-3With Torr
Adjust so that As a result, the plasma generation means 1
Arc discharge occurs near the cathode and the discharge gas is plasmified.
Be converted The generated plasma is generated by the first intermediate electrode 2
By applying a predetermined voltage to the first and second intermediate electrodes 22,
It is introduced into the plasma introduction unit 2. This plasma is
Permanent magnet (not shown) built in the intermediate electrode 21 of the
A second air-core coil (shown in the figure) built in the second intermediate electrode 22.
The magnetic field (magnetic field) formed by the
Depending on the field), it is directed to the pressure adjustment chamber 5 in a state of being focused in a cylindrical shape.
Kau. Then, during the process, the first magnetic field is applied as described above.
The sheet-like plasm which has been transformed into the sheet-like shape by the means 3.
And becomes accelerated by the voltage applying means 14,
In this state, it is introduced into the pressure adjusting chamber 5. The first magnetic field
The applying means 3 is based on the width of the deformed sheet-shaped plasma 15.
Set to be wider than the width of the plate 11 (400 to 500 mm).
Has been. Further, by the second magnetic field applying means 3a, the screw
This is corrected, the uniformity is improved, and the film is introduced into the film forming chamber 6.
At that time, the sheet-shaped plasma 15 is generated by the third magnetic field applying means.
It is bent by 90 ° by 7 and focused on the anode 16.

Thereafter, the pressure in the first chamber and the pressure in the second chamber are adjusted to 5 × 10 ^-2 Torr by using the exhaust means connected to the exhaust ports 13b and 13c. In this state, the gate valve 17 is opened, and the substrate supporting means 12 adjusts the position of the substrate supporting means 12 so that the distance between the sheet-shaped plasma 15 and the substrate 11 is about 50 mm. In this state, CH ₄ (methane) as a reaction gas is introduced into the first chamber from the gas supply means 9 at a flow rate of 2 cc / s. It should be noted that the exhaust means is adjusted so that the pressure in the film forming chamber is maintained at 5 × 10 ⁻² Torr even after the introduction of the reaction gas.

The CVD conditions and the film thickness distribution of the substrate 11 in this embodiment are shown below. Achieved vacuum degree in the vacuum container: 5 × 10 ^-6 Torr Vacuum degree in the pressure control chamber: 5 × 10 ^-4 Torr Vacuum degree in the film formation chamber during film formation: 5 × 10 ^-2 Torr Arc discharge voltage: 100 V arc Discharge current: 100 A Acceleration voltage: 120 V Reaction gas flow rate: 2 cc / s Distance between substrate and sheet-like plasma: 50 mm Deposition rate (rate): 300 nm / min Film thickness: 1 μm Substrate film thickness distribution: ± 3% [Implementation] Example 2] FIG. 2 is a schematic sectional view of a main part of a plasma CVD apparatus according to a second aspect. With respect to the configuration and function of the device, the same reference numerals are used in common with FIG.

An amorphous carbon thin film was formed in the same manner as in Example 1. The film forming conditions and the film thickness distribution of the substrate 11 at that time are shown below. Degree of vacuum reached in the vacuum container: 1 × 10 ^-5 Torr Vacuum degree of the film forming chamber during film formation: 1 × 10 ^-3 Torr Arc discharge voltage: 80 V Arc discharge current: 90 A Reaction gas flow rate: 2 cc / s Substrate Distance from sheet-like plasma: 50 mm Deposition rate (rate): 120 nm / min Film thickness: 1 μm Substrate film thickness distribution: ± 3% [Comparative example] Conventional sheet plasma CVD apparatus
-215671) was used to form an amorphous carbon thin film in the same manner as in Example 1. The film forming conditions and the film thickness distribution of the substrate 11 at that time are shown below. Degree of vacuum reached in the vacuum vessel: 1 × 10 ^-5 Torr Vacuum degree in the vacuum vessel during film formation: 1 × 10 ^-3 Torr Arc discharge voltage: 60 V Arc discharge current: 70 A Reaction gas flow rate: 4 cc / s Substrate and sheet Distance from plasma: 50 mm Film formation rate (rate): 100 nm / min Film thickness: 1 μm Substrate film thickness distribution: ± 8% As can be seen by comparing the present example with the comparative example, It is excellent in terms of film speed, uniformity of film thickness distribution, and use efficiency of reaction gas.

[0023]

According to the present invention, since plasma generated by arc discharge is accelerated by the voltage applying means, neutral active species having high energy can be obtained from the reaction gas. Therefore, the dense film of the film obtained on the substrate can be obtained. Properties and adhesion are improved. Further, since the plasma density is high, there is an advantage that the film forming speed is fast, which is suitable for mass production. Further, since the sheet plasma is used, the uniformity of the formed film thickness is improved, which is suitable for forming a large area film. Further, in the present invention, the reactive species that contribute to the thin film formation are mainly neutral active species, so that there is an advantage that the physical properties of the obtained film, particularly the electrical characteristics are improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a plasma CVD apparatus according to an embodiment (Example 1) of the present invention.

FIG. 2 is a schematic cross-sectional view of a plasma CVD apparatus according to one example (Example 2) of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma generation means 2 Plasma introduction part 3 1st magnetic field application means 3a 2nd magnetic field application means 4 Air core coil 5 Pressure adjustment chamber 6 Film-forming chamber 7 3rd magnetic field application means 9 Gas supply means 11 Substrate 12 Substrate support Means 13 Exhaust port 14 Voltage applying means 15 Plasma flow 16 Anode 17 Gate valve 18 Accelerating power source 19 Main power source 20 Ar gas inlet port 21 First intermediate electrode 22 Second intermediate electrode or more

Claims (4)

[Claims] 1. A first step of generating plasma by arc discharge, a second step of shaping the plasma into a sheet by a magnetic field, a third step of bending the sheet of plasma by a magnetic field, and a bending of the sheet of plasma. A plasma CVD method comprising a fourth step of forming a thin film by a gas phase reaction on a substrate placed in the preceding plasma traveling direction. 2. A plasma generating means for generating plasma by arc discharge, a magnetic field applying means for deforming the shape of the plasma into a sheet shape, a supporting means for supporting a substrate, and the sheet-like shape from the side facing the substrate. Gas supply means for supplying a reactive gas through plasma, magnetic field applying means for bending the sheet-like plasma, film forming chamber for holding the substrate at a predetermined pressure, and the film forming chamber at a predetermined pressure Plasma CV composed of exhaust means for setting
D device. 3. A first step of generating plasma by arc discharge, a second step of shaping the plasma into a sheet by a magnetic field, a third step of accelerating electrons in the sheet of plasma, and the sheet of plasma. Is a magnetic field, and a fourth step of bending the sheet-shaped plasma by a magnetic field, and a fifth step of forming a thin film by a gas phase reaction on a substrate placed in the direction of advance of the plasma before bending the sheet-shaped plasma. 4. Plasma generation means for generating plasma by arc discharge, magnetic field application means for deforming the shape of the plasma into a sheet shape, voltage application means for accelerating electrons in the sheet-shaped plasma, and substrate. Supporting means for supporting the substrate, a film forming chamber for holding the substrate at a predetermined pressure, a pressure adjusting chamber installed between the plasma generating means and the film forming chamber and set to a pressure lower than that of the film forming chamber. ,
Exhaust means for setting the pressure adjusting chamber and the film forming chamber to predetermined pressures, gas supply means for supplying a reaction gas from the side facing the substrate through plasma in the film forming chamber, and the film forming A plasma CVD apparatus including a magnetic field applying unit for bending the direction of plasma in a room.