JPH07161486A - Method for generating electron acceleration type sheet plasma - Google Patents

Abstract

PURPOSE:To obtain a plasma CVD at a large area and at a high speed to perform the sputtering and etching by accelerating an electron component of a direct current discharge plasma flow at a large current, and changing the shape of the plasma flow from a cylindrical plasma flow to a sheet-like plasma flow. CONSTITUTION:Ar is supplied from a discharging negative electrode 2 to obtain a predetermined Ar gas pressure, and a predetermined voltage is applied between positive electrodes 12 to form a plasma flow at a predetermined diameter. This initial plasma flow is led to an intermediate area at a low gas-pressure along a magnetic field by a discharging pump 8. A cylindrical plasma current is deformed into a sheet-like plasma flow 7 at a predetermined width and thickness by a permanent magnet 9 formed with a pair of N, S poles facing to each other, and the sheet-like plasma flow 7 passes through a slit 11, and led to the area of the accelerating positive electrodes 12, and the Ar gas 13 is led to obtain a predetermined pressure, and a predetermined acceleration voltage is applied between the discharge area and the accelerating electrodes 12. An electron accelerating sheet plasma 14 is thereby stably generated.

Description

Detailed Description of the Invention

[Industrial field of application] A plasma CVD apparatus with a large area and a high film-forming rate, a sputtering device is a metal,
Long-awaited for surface treatment of glass, plastic, etc. Similarly, a large-area and high-speed plasma etching apparatus is also desired for fine processing. The plasma generation method of the present invention can sufficiently meet these expectations.

[Prior Art] (1) A typical large-area plasma CVD apparatus in the related art utilizes plasma generation by electron cyclotron resonance of microwaves. However, since the increase of the plasma density and the increase of the area are exhausted, the plasma having a diameter of about 20 cm is the limit. Further, a strong magnetic field of 1 KG or more, abnormal discharge due to local electric field concentration when power is increased, and substrate damage due to high electron temperature are major obstacles. The glow discharge type CVD apparatus other than the microwave type has a remarkably low plasma density, and the RF discharge type CVD apparatus is far from the microwave type because of damage to the substrate due to plasma self-potential and complexity of the antenna. . (2) A flat plate magnetron type is considered to be the representative of the sputtering device, and it has a considerably large volume of 10 mA / c.
A target ion current density of about m ² can be obtained. However, the drawbacks are that the bias voltage of the target and the ion current to the target cannot be changed independently, the neutral gas pressure is too high due to the glow discharge, and the distance between the target and the substrate is limited. Damage and, finally, insufficient ionization of the reactive gas in the case of reactive sputtering. Other types of sputtering devices do not pose a problem in terms of ion current density and large area. (3) Regarding the plasma etching apparatus, the microwave type is considered to be the representative, as in the plasma CVD. Therefore, the same drawbacks as those of the plasma CVD apparatus occur. That is, the area limit, strong magnetic field, abnormal discharge, and substrate damage. (4) Now, when the DC discharge plasma flow (generally columnar) along the magnetic field is converted into a sheet shape by the method using a pair of permanent magnets invented by Uramoto (“Vacuum”, Vol. 25, p. 719), the conventional apparatus is used. It has already been clarified that it will be a large-scale, unique CVD device, sputtering device, and etching device. However, the weak point of the (A) CVD apparatus is 3 × 10 ⁻³ Tor required for high-speed film formation.
That is, the discharge becomes unstable at a high reaction gas pressure of about r or higher. This is due to a significant decrease in the ionization efficiency due to the energy decay of the electron flow in the discharge plasma.
(B) The weak point of the sputtering device is that the deep negative bias voltage applied to the target limits the approach distance of the target to the surface of the sheet plasma flow, and the ion current density to the target can be suppressed low. This is because the electron energy in the general DC discharge plasma is low, and the central plasma electron flow is blocked by the negative bias voltage of the target. Further, at this low electron energy, the ionization efficiency is small and the plasma density is relatively low, so that the relative ion current density to the target is also low. (C) A weak point of the etching apparatus is that when an etching reaction gas is introduced, generally, negative ions are generated, so that the plasma electron flow is disturbed and the discharge becomes unstable. Above (A),
The common point of the weak points of (B) and (C) is the lack of electron energy in a general DC discharge plasma flow. For example, in a normal argon gas discharge, the electron energy component of the central electron flow is limited to about 25 eV. This electron energy has the maximum ionization efficiency (about 15 ion pairs / cm 2) in argon gas.
It is in the region of low ionization efficiency (about 5 ion pairs / cmTorr at 25 eV) compared to 80 eV which gives Torr). Thus, the sheet plasma invented by Uramoto also has superior properties to the microwave type and the flat plate magnetron type, but the lack of electron energy during general DC discharge becomes an obstacle, and its features cannot be exhibited. is there.

[Problems to be Solved by the Invention] It is a problem to raise the electron energy of the sheet plasma flow already invented by Uramoto to bring out its characteristics as a plasma CVD, sputtering and etching apparatus. That is,
(1) The plasma CVD apparatus accelerates the electrons in the discharge plasma flow so that the electrons can travel a long distance even under a high gas pressure and the ionization efficiency becomes high. (2) As the sputtering device, even if the target is brought close to the sheet plasma surface in the center, the discharge plasma flow is not disturbed by the negative bias voltage applied to the target, and the discharge is performed so as to maximize the ionization efficiency. Accelerate the electrons in the plasma stream. (3) As a plasma etching device, negative ions generated by the introduction of the reaction gas for etching accelerate electrons in the discharge plasma flow so that the discharge does not become unstable, and also maximize the ionization efficiency. Accelerate the electrons in the discharge plasma stream.

[Means for Solving the Problems] The principle and apparatus for accelerating electrons in a DC discharge plasma flow along a magnetic field are as follows:
It has already been published in Uramoto's paper "Vacuum" Vol. 20, p. 170, vol. 26, p. That is, the high gas pressure region (1
The Torr~2 × ¹⁰ -3 Torr) hot cathode plasma stream generated by the, evacuated to a lower intermediate area ^{(about 10} -4 Torr~8 × 10 -4 Torr gas pressure along the magnetic field) to Guided, then accelerated anode area with gas pressure higher than this intermediate area (long space and gas introduction required)
To set. Electron acceleration of the discharge plasma flow is performed by applying an acceleration voltage to this intermediate region. This principle is to stably accelerate while neutralizing the electron flow by the ion backflow from the accelerating anode region to the intermediate region. Next, the principle and apparatus for transforming a direct-current discharge plasma flow along a magnetic field into a sheet shape have also been published in the paper "Vacuum", Vol. 25, p.
That is, a pair of permanent magnets having the same poles and facing each other are arranged on both sides of the DC discharge plasma flow (cylindrical shape) along the magnetic field to change from the cylindrical shape to the sheet shape. The present invention is unique in that, in the intermediate region between the discharge anode and the accelerating anode, the cylindrical plasma flow is transformed into the sheet plasma flow simultaneously with electron acceleration. That is, electron energy is increased by electron acceleration,
The surface area of the plasma flow was expanded by sheet deformation. The means is simply expressed by placing a vacuum pump in the middle of the DC discharge path, applying a voltage between them, and disposing a pair of permanent magnets.

[Operation and Examples] The method of carrying out the present invention and the experimental results will be described as an example. First, a cylindrical plasma flow of argon is generated in the discharge anode region by a hot cathode DC discharge along a magnetic field as shown in FIG. In the first experimental example, 10 SCCM of argon gas was supplied from the discharge cathode side.
The discharge current is about 50 A, the voltage between the discharge cathode and the discharge anode is about 25 V, and the argon gas pressure in the discharge anode region is about 3 × 10 ⁻³ Torr. The diameter of the glowing plasma stream is about 10 mm. This initial discharge plasma stream is then directed along the magnetic field to an intermediate region that is evacuated by a vacuum pump to a lower gas pressure (5 × 10 ⁻⁴ Torr). Further, the cylindrical plasma flow from the discharge anode is transformed into a sheet-shaped plasma flow having a width of about 10 cm and a thickness of about 3 mm (the portion where plasma is shining) by a permanent magnet having a pair of opposite electrodes facing each other. This sheet-deformed plasma flow has a slit (10 cm x
1.5 cm) and is guided to the accelerating anode region. An acceleration voltage of about 100 V is applied between the discharge anode region and the accelerating anode region to accelerate the electron component of the plasma flow. Argon gas was introduced into the accelerated anode region to about 10 ⁻³ Torr. In this manner, electron-accelerated sheet plasma (length 40 c
m, width approximately 13 cm) was produced. In order to test this electron acceleration type sheet plasma for sputtering,
A metal plate having a width of 12 cm and a length of 33 cm (about 400 cm ² ) was placed in parallel with the shining sheet plasma surface, and the distance was brought close to about 5 mm. Thus, this metal plate is used as a target for spattering with respect to the acceleration anode by −20.
The electron-accelerated sheet plasma flow was stable even when 0 to -500 V was applied. The ion current to the target was about 7.5 A, and the argon ion current density reached about 19 mA / cm ² . This average plasma density is about 5 × 10 ¹¹ / cc when the electron temperature is 5 to 6 eV. In this experiment, an electron acceleration type discharge of 200 A or more is also possible, so the ion current density to the tart is 70 m
A / cm ² or more can be expected. The width of the sheet plasma can be 40 cm and the length can be about 1 m. In this first experiment, the ion current to the tartat reached about 15% of the total discharge current, so that the discharge current efficiency was surprising as compared with the conventional method. In the second experimental example, for the plasma CVD apparatus, the slit at the entrance to the acceleration anode region was reduced to 9 mm with a width of 10 cm, and argon gas was introduced into the acceleration anode region. Thus, the gas pressure in the intermediate region is 8
× 10 ⁻⁴ Torr, the gas pressure in the acceleration anode region is 1.5
The experiment was conducted by raising the pressure to × 10 ⁻² Torr. Discharge current 2
0A to 100A, electron accelerating voltage of 80V to 150V in the intermediate region, width of about 13cm and length of 40c in the accelerating anode region
m sheet plasma was stably generated. Thus, it can be considered that the plasma CVD apparatus has a high gas pressure.

[Effects of the Invention] According to the present invention, a plasma CVD apparatus for large area, high speed film formation, which is impossible with the prior art,
It became clear that a sputtering device could be made. In particular, regarding the diamond film, which is currently attracting attention, the prospect of a large area of 10 ⁻² Torr or more of reaction gas and large current discharge plasma CVD has been opened. Even for large-area, high-speed plasma etching equipment that is impossible with conventional technology, electron-acceleration type plasma has already been demonstrated in a small area, so this electron-acceleration type sheet plasma combined with sheet plasma technology and large-current acceleration technology is sufficient. Can be expected.

[Brief description of drawings]

FIG. 1 is a device configuration diagram of the present invention.

FIG. 2 is a sectional view of a slit and a sheet plasma of the device of the present invention.

[Explanation of symbols]

1 is a cylindrical plasma flow in a discharge anode 2 is a discharge cathode 3 is a (carrier) gas 4 is a discharge power supply 5 is an acceleration power supply 6 is an exhaust pump 7 is a sheet (plasma) deformation part 8 is an insulating tube 9 is a pair of (permanent) prismatic permanent Magnet 10 is (two) magnetic field coil 11 is slit (part of acceleration anode) 12 is acceleration anode 13 is reaction gas 14 is electron acceleration sheet plasma

Claims (1)

[Claims] 1. A method of accelerating electrons in a DC discharge plasma flow and converting them into a sheet shape (a wide width and a thin shape) by a magnet.