JPS63143798A - Automatic controller for microwave plasma generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an automatic control device for a microwave plasma generator;
More specifically, the present invention relates to an automatic control device used in a plasma generator that generates plasma by an electron cyclotron resonance phenomenon.

[Conventional technology]

Plasma that generates plasma by supplying microwaves of frequency ω into a magnetic field B = ωm/e (m is the mass of the electron and e is the charge of the electron) with a strength that satisfies the conditions for generating electron cyclotron resonance. Generators are known.

[Problem that the invention seeks to solve]

In the plasma generator using electron cyclotron resonance described above, it is necessary to supply microwaves to a discharge tube filled with a desired type of gas at a desired pressure. The conditions of the plasma that enters the discharge tube change, and the load conditions of the microwave input to the discharge tube change. Then, in response to changes in load conditions, it was necessary to find the optimum microwave conditions corresponding to the load by moving the microwave matching system, such as the three-stub, E-H tuner, back plunger, etc. Furthermore, when changing the power of the manual microwave, such a matching operation is required, which is very complicated and inefficient.

[Means for solving problems]

The above-mentioned problems include: a microwave generator that generates microwaves, a means for supplying power to the microwave generator, a plasma generation chamber into which the microwaves are introduced and plasma is generated inside, and plasma generation using microwaves. means for measuring the value of a control parameter related to the control parameter; means for storing the set value of the control parameter; a comparison circuit for comparing the set value stored in the storage means with the measured value of the control parameter; means for controlling the power supplied to the microwave generator according to an output signal from the circuit; a standing wave measuring device for measuring the standing wave ratio or reflection coefficient of the microwave; and a means for measuring the intensity of the incident microwave wave. A matching device that changes the ratio to the intensity of a reflected wave, and a means for driving and controlling the matching device according to the standing wave ratio or reflection coefficient obtained by the standing wave ratio measuring device. This problem is solved by the automatic control device for a microwave plasma generator of the invention.

[For production]

The values of control parameters related to plasma generation by microwaves, such as ion current, plasma electron temperature, and supplied microwave power, are measured and compared with preset and memorized set values, and the values are sent to the microwave generator according to the comparison results. power supply is controlled.

At the same time, the standing wave ratio or reflection coefficient of the microwave is measured, and the matching device is driven and controlled according to this measured value.

〔Effect of the invention〕

According to the invention, desired plasma parameters can be obtained automatically and with maximum efficiency.

Even if the plasma conditions change depending on the type of gas filled in the plasma generation chamber, the pressure, or the power of the input microwave, and the load conditions of the microwave manually applied to the plasma generation chamber change, the matching operation will be performed automatically. Since the desired plasma parameters can be obtained, the operation of the micro-plasma generator becomes extremely simple.

〔Example〕

Hereinafter, the present invention will be explained in detail based on examples. 1st
The figure shows a first embodiment of the present invention, in which an ion current is used as a control parameter. Microwaves generated by a microwave generating means 1 such as a magnetron are transmitted through a waveguide 2 and introduced into a plasma generation chamber 3, where plasma is generated. A standing wave ratio measuring device 4 and a matching device 5 are inserted between the microwave generator 1 and the plasma generation chamber 3. The matching conditions change depending on the type of gas in the plasma generation chamber 3, gas pressure, etc.
The standing wave ratio of the microwave flowing into the waveguide 2 changes, and the standing wave ratio at this time is measured by the standing wave ratio measuring device 4, and the matching unit driving means 6 changes the standing wave ratio. The matching box 5 is controlled so that the value is minimized.

Ions in the plasma generated in the plasma generation chamber 3 are extracted by the ion extraction means 7, and the ion current is measured by the ion current value measuring means 8. The value is input to one side of the comparator 9. The other input of this comparator 9 is manually inputted with the ion current value stored in the means for storing the ion current set value. From the output of the comparator 9, an output having a value corresponding to the difference between the two human powers is generated, and is supplied to the power supply control means 11. This power supply control means 11 controls the power supply 1 in response to this manual shift.
2 to control the microwave power generated by the microwave generator 1. Therefore, even if the gas type, gas pressure, etc. in the plasma generation chamber 3 change, the set ion current can be obtained with minimum power consumption.

FIG. 2 shows a second embodiment of the present invention, in which one of the plasma parameters in the plasma generation chamber, such as the plasma electron temperature, is used as the control parameter. In this embodiment, the electron temperature in the plasma generation chamber 3 is measured by the probe 18, and the measured value and the electron temperature set value stored in the means 20 for storing the electron temperature set value are compared by the comparator 9. be done. The output of the comparator 9 generates an output with a value corresponding to the difference between the two inputs, and the first
The microwave power source 12 is controlled in the same manner as in the embodiment.

FIG. 3 shows a third embodiment of the present invention, and shows pl in the case where microwave power supplied to the plasma generation chamber 3 is used as a control parameter. In this embodiment, the power of the microwave supplied into the plasma generation chamber 3 is measured by the power measuring means 28, and the microwave power is stored in the means 30 for storing the measured value and the microwave power setting value. The set value is compared by the comparator 9, and the microwave power source 12 is similarly controlled according to the result.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a first embodiment of the present invention, FIG. 2 is a schematic diagram of a second embodiment of the present invention, and FIG. 3 is a schematic diagram of a second embodiment of the present invention.
FIG. 2 is a schematic diagram of an example. 1... Microwave generator, 2... Waveguide, 3... Plasma generation chamber, 4... Standing wave ratio measuring device, 5... ...Matching box, 6...
Matching device driving hand, 7... Ion extraction means, 8... Ion current measuring means, 9... Comparator, 10... Ino current setting residue storage means, 1
1... Supply power control means, 18... Probe, 20... Electronic temperature set value storage means, 2
8...Power measuring means, 30...Microwave setting value storage means.

Claims (4)

[Claims] (1) A microwave generator that generates microwaves, means for supplying power to this microwave generator, a plasma generation chamber into which the microwaves are introduced and plasma is generated inside, and related to plasma generation by microwaves. means for measuring the value of the control parameter to be measured; means for storing the set value of the control parameter; a comparison circuit for comparing the set value stored in the storage means with the measured value of the control parameter; means for controlling the power supplied to the microwave generator according to the output signal of the microwave, a standing wave measuring device for measuring the standing wave ratio or reflection coefficient of the microwave, and the intensity of the incident wave and the reflected wave of the microwave. and a means for driving and controlling the matching device according to the standing wave ratio or reflection coefficient obtained by the standing wave ratio measuring device. Automatic control device for generator. (2) The control parameter is an ion current value of the ion beam obtained by extracting the ions being generated in the plasma.
The automatic control device described in section 1). (3) Claim (1) characterized in that the control parameter is an electron temperature during plasma generation.
Automatic control device as described in section. (4) The automatic control device according to claim (1), wherein the control parameter is a power value of microwaves sent into the plasma generation chamber.