JPH03297098A - Plasma generating device - Google Patents

Abstract

PURPOSE:To accomplish a plasma generating device to generate plasma which has a large bore and is as flat as practicable, by performing TEon mode excitation with microwave power in a metal cylinder, applying a mag. field corresponding to the excited frequency, and thereby generating cyclotron resonance. CONSTITUTION:One end face in axial direction of a metal cylinder 1 is sealed with a metal plate 12, and microwave power is supplied from a terminal 2 so as to make TEon mode excitation, and the inside of a plasma chamber 1 is put in a required intensity of magnetic field using an excitation coil 3 or a permanent magnet. A gaseous substance is fed to the plasma chamber 1 from a plasma substance cast-in hole 4. Because a magnetic field of such an intensity as to generate absorption of cyclotron resonance is applied around this cast-in hole 4, plasma is ignited, dispersed in the chamber 1 following the stream of the gas, and equalized. As this plasma stream is excited by the microwave power in the TEon mode, the diameter becomes large. This allows uniform generation of plasma having a large bore.

Description

[Detailed description of the invention] [Industrial application field] The field of application of plasma generators is expanding every year.

Plasma generators can generate electrons, ions, ion radicals, etc., especially in the electronics industry.
The extracted ion beam is used in a wide variety of applications, including ion implantation, ion blating, crystal growth, sputtering, etching, and compound synthesis.

The present invention relates to a plasma generation device that supplies microwave power to generate plasma and extracts an ion beam.

[Conventional technology]

Electron cyclotron resonance absorption (ECR) is used in various fields as a plasma generation device because microwave power effectively heats electrons and creates high-density plasma through the interaction of magnetic fields and electrons. It is difficult to generate plasma as flat as possible with a diameter larger than that of a tumor.

[Problem to be solved by the invention]

Conventionally, various systems have been announced as plasma generators using ECR, but all of them use single mode excitation, and therefore cannot generate large-diameter plasma.

In the present invention, TEon mode excitation is performed using micro-power in a large-diameter metal cylinder, and a magnetic field corresponding to this frequency is applied to generate cyclotron resonance, thereby generating a large-diameter, flat plasma as possible. The purpose is to provide a plasma generator.

[Means for solving the lI problem]

The present invention relates to a metal cylinder into which an ionized substance is injected, a microwave power supply means for exciting a TEon mode from one axial end face of the cylinder via a plurality of loop coils or a narrow gap, and This plasma generation device is characterized by having a magnetic field generating means that applies a magnetic field corresponding to a microwave frequency from the outside to cause electron cyclotron resonance absorption.

[For production]

There are two types of resonance modes in a metal cylinder: TE waves and TM waves.In the former, the electric field does not touch the conductor, but in the latter, the electric field cuts the conductor, resulting in large losses and poor efficiency. The invention employs TEon mode excitation, which is a higher-order mode of TE waves. The 0 at the beginning of the subscript of the mode signal indicates that there is no change in the electromagnetic field in the circumferential direction, and the next n indicates the number of changes in the radial direction. If both axial ends of this metal cylinder are closed with metal plates, a resonator is formed and this mode is expressed in the form TEon-, where m is the number of changes in the electromagnetic field in the axial direction. is expressed. A longitudinal cross-sectional view of the electromagnetic field of the TE, 21 resonator is shown in FIG. 2, and a cross-sectional view is shown in FIG. 3. In Figures 2 and 3, 1 is a plasma chamber;
2 is an input terminal for microwave power, 71 and 72 are electric field distributions, 8 is a magnetic field distribution, and 12 and 13 are metal plates.The plasma chamber 1 has a metal cylinder structure, and the axial direction of the cylinder is Both end faces are closed with metal plates 12 and 13. It electric field distribution The magnetic field distribution also does not touch the metal wall surface, so the loss due to this is slight. 0 The figure shows the case where n is 2, but in general it is a 0 layer. 0 In the present invention, the micro Since the wave power is applied, the plasma excitation part becomes n times the single mode excitation and spreads inside the large diameter metal cylinder, so that the purpose can be achieved.

In the case of a TEon type valve vibrator, if the diameter is less than the minimum value, it will be attenuated and propagation in the axial direction will not be possible, so the diameter must be greater than the minimum value. The cutoff wavelength λC for each propagation mode and the minimum diameter I)+in for a frequency of 2.45 GHz have the relationship shown in the table below.

Its resonance length (■) is determined by Keyaki in the table below.

If the frequency used now is 2.45 GHz, its wavelength λ
0 becomes λo-122.364■, and since the resonance length of the resonator and ■ is the tube wavelength ('A), it can be determined by the following equation.

L=λO/2/ (1-(λ0/λC)ri @4 Therefore, if several diameters of resonators with a working frequency of 2.45 GHz are selected to be greater than or equal to the minimum diameter Dmin, as shown in the table above, TE
In the on+ mode, increasing the diameter will shorten the resonance length, so to lengthen L, set the TEon- mode, and the wavelength can be multiplied by m.

In electron cyclotron resonance, the interaction of a magnetic field and microwave power can selectively heat plasma electrons to create a high-density plasma.

Electron cyclotron frequency f (GHz) and magnetic field strength B
(kGauss) has the following relationship.

f=2.8B, that is, at f=2.45 (GHz), B=0°875
(kGauss). However, the magnetic field strength does not need to be at this value over the entire surface of the plasma generation chamber; in particular, a magnetic mirror effect should be performed in the area where the plasma is ignited near the ionized substance inlet and near the exit of the plasma generation chamber. Therefore, the magnetic field strength should be adjusted to this value.

〔Example〕

FIG. 1 is a longitudinal sectional view for explaining the present invention in detail.

1 is a plasma chamber made of a metal cylinder, one end surface in the axial direction of this metal cylinder is sealed with a metal plate 12, and the TEon
Microwave power is supplied from terminal 2 to perform mode excitation. 3 is an excitation coil or a permanent magnet to maintain the required magnetic field strength inside the plasma chamber 1; 4 is a plasma material inlet for feeding gaseous substances into the plasma chamber 1 from multiple directions; the inside of the plasma chamber 1 is 10-" to 10”3To
I keep it around rr. Since a magnetic field strong enough to cause cyclotron resonance absorption is applied near the plasma material inlet 4, the plasma is ignited, diffused into the plasma chamber 1 according to the gas flow, and is averaged. Since this plasma flow is excited by microwave power in the TEon mode, it has a large diameter. A large number of small holes are bored in the metal plate 13 at the other end of the plasma chamber 1, and due to the potential difference with the ion extraction electrode 5, a thick ion beam 6 is extracted to the outside.

FIG. 4 shows the state in which microwave power is supplied by the loop coil, as seen from inside the plasma chamber 1. TEon
In mode excitation, the magnetic field around the end face is oriented in the diametrical direction as shown in Figures 2 and 3, so the loop coils 21 and 22 should be oriented perpendicular to the magnetic field. Install them so that their adjacent excitation phases are opposite. Furthermore, since the plasma chamber is in a low vacuum state, the loop attachment portion of the metal plate 12 is sealed with a heat-resistant insulator 9.

That is, in FIG. 4, the loop coil 21 is drawn into the plasma chamber from a position 211 of the heat-resistant insulator 9, then bent to the left in the drawing, further bent, and then joined to the metal plate 12. Since the loop coil 22 is drawn in from the opposite direction to the loop coil 21, it is drawn into the plasma chamber from the position W221.

When microwave vibration is performed from a waveguide through a gap, microwave power is supplied from the waveguide 11 through a gap 10 cut at right angles to the magnetic field, as shown in FIG. In this case as well, the excitation phases of adjacent slits 10 are configured to be opposite, and the slits are sealed with a heat-resistant insulator to maintain airtightness.

In the present invention, when using a large resonator, the problem is how to suppress the TM mode. Although it is a different mode resonance, the TEon mode is particularly problematic because its dimensions match those of the TM and n modes.

In TM and n modes, the electric field and magnetic field of TEon are reversed, so microwave current flows within the resonator wall and loss increases. Therefore, in the present invention, the configuration shown in FIG. 6 was attempted as a heterogeneous mode suppressor. FIG. 6 is a partial longitudinal sectional view of the end face of the cylinder of the plasma chamber, showing the cylinder 101 and the metal plate 1.
A heat-resistant insulating ring 91 is inserted between 21 to increase the electrical loss of TM mode resonance. The heat-resistant insulating ring 91 is used as a suppressor of the TM mode of different mode resonance.

In this example, the microwave power source is 2.45 GHz, 5
kW, the plasma chamber dimensions are 320cm in diameter,
Using length 235.7 (TEO22 mode),
A magnetic field of 875 gauss was applied externally by an excitation coil. As a result, highly efficient, large-diameter, almost uniform plasma generation was observed in many samples.

〔Effect of the invention〕

According to the present invention, large-diameter plasma of 200 mm to 500 square meters can be generated uniformly with high efficiency.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of the plasma generating device of the present invention, and FIG.
The figure is TE6. , FIG. 3 is a cross-sectional view of the IT magnetic field of the resonator, FIG. 4 is a diagram showing an example using a loop coil, and FIG. 5 is an example using microwave vibration due to a slit. The figure shown in FIG. 6 is a longitudinal sectional view of the suppressor. 1 is a plasma chamber, 2 is an input terminal, 21 and 22 are loop coils, 3 is an excitation coil or permanent magnet, 4 is a plasma material inlet, 5 is an ion extraction electrode, 6 is an ion beam, 71 and 72 are electric field distributions, 8 is a magnetic field distribution, 9 is a heat-resistant insulator, 10 is a slit, 11 is a waveguide, 12, 13, and 121 are metal plates, 91 is a heat-resistant insulating ring, and 101 is a cylinder. Figure 3

Claims (2)

[Claims] (1) A metal cylinder into which an ionized substance is injected, a microwave power supply means for exciting the TEon mode from one axial end face of the cylinder via a plurality of loop coils or slits, and the outside of the cylinder. 1. A plasma generation device comprising magnetic field generating means for applying a magnetic field corresponding to a microwave frequency to cause electron cyclotron resonance absorption. (2) TM of microwave power between the cylinder and the axial end face
The plasma generator according to claim 1, further comprising a suppressor for suppressing supply of the mode.