JP2836509B2 - Magnetron drive power supply and plasma generator having the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron drive power supply and a microwave plasma generator using the same, and more particularly to a drive power supply for a plurality of magnetrons.
The present invention relates to a microwave plasma generator that oscillates a plurality of microwaves using the same and generates uniform microwave discharge plasma by the interaction of these microwaves.

[0002]

2. Description of the Related Art In recent years, a plasma generator using microwaves has been used as an excitation source of a gas laser.
Various application studies have been conducted.

[0003] This is because, in the first place, in pumping for a gas laser by microwaves, the input power per unit volume can be increased in principle as compared with other pumping methods, and therefore the apparatus can be downsized. This is because it is considered to have a technical advantage.

[0004] Furthermore, as for the power supply, it is sufficient to use an inexpensive magnetron such as those on the market in terms of output, and it is considered that if such a magnetron can be mounted, there is a great cost advantage. .

[0005] Specifically, although the research and development on the excitation of the gas laser has been actively carried out in the early 1970's, it is actually very difficult to spread the plasma uniformly, and other effective methods are also available. Excitation means (RF excitation, etc.)
After that, R & D was gradually declining after that.

However, in the field of CVD technology, research and development of a technique for decomposing gas using microwave plasma have become active, and in response to this, research and development as a gas laser excitation source has recently been performed again. It has become.

As a conventional attempt to obtain a uniform discharge in microwave excitation in a plasma generator, a microwave is introduced into a discharge portion from two directions, and the discharge is caused by the interaction of the two microwaves. There has been proposed a configuration for uniformly spreading (JP-A-3-111577).

In Japanese Patent Application Laid-Open No. 3-111577,
Although there is no specific description regarding the oscillation waveform of the microwave, it is considered that the two microwaves need to have substantially the same oscillation output in order to spread the plasma uniformly.

This is because if the oscillation output of one of the magnetrons is large, the electric field on one of the magnetrons becomes strong, making it difficult to obtain a uniform discharge.

FIG. 3 is a schematic structural view of a plasma generating applicator of such a microwave plasma generating apparatus, and will be described in more detail with reference to FIG.

In FIG. 3, 7a and 7b are magnetrons, 12a and 12b are microwave waveguides, 13 is a plasma generation tube made of a dielectric material such as a quartz glass tube, 14a and 1b.
4b is a load impedance matching device, 15a and 15b are directional couplers, 16a and 16b are reflection ends, 17a and 17b
Is a standing wave of a microwave, 18a and 18b are microwaves which are oscillated and travel, and 19a and 19b are microwaves which are reflected and travel.

In such a configuration having a plurality of magnetrons, the microwaves 18a and 18b oscillated from the two magnetrons 7a and 7b are connected to the microwave waveguide 1
The gas is absorbed by the gas flowing through the plasma generating tube 13 through 2a and 12b to generate plasma.

Here, the load impedance matching units 14a and 14b are adjusted so that the electrical impedance of the plasma of the plasma generating unit and the impedance of the magnetron are matched and the reflections 19a and 19b of the microwave are minimized.

This adjustment is performed by the directional couplers 15a and 15b.
When the impedance is matched while measuring the reflected wave power in the above, the microwave is almost completely consumed by the generation of plasma.

Further, since the reflected waves 19a and 19b are suppressed in the matching units 14a and 14b, that is, the microwaves 18a and 18b form a cavity resonator, the microwaves 18a and 18b are connected to the matching units 14a and 14b and the reflection ends 16a and 16b. Standing waves 17a and 17b are formed between the two.

Since the plasma generating tube 13 is located at the antinode of the standing waves 17a and 17b of the microwave, a discharge is efficiently generated in the plasma generating tube 13 by the high electric field of the microwave. The gas is also efficiently converted into plasma.

When such a plasma generating apparatus is used for a gas laser, the plasma generating tube 13 is a dielectric cylinder, in which gas flows in a direction perpendicular to the plane of the drawing to form a laser resonator. The mirrors are installed at both ends of the plasma generating tube 13 so that the oscillated laser light is taken out perpendicular to the plane of the drawing.

On the other hand, in a CVD apparatus, a reaction vessel for using a plasma gas for a reaction is installed, for example, in front of the paper.

FIG. 4 shows a typical magnetron control circuit for a conventional microwave plasma generator having a plurality of magnetrons.

In FIG. 4, reference numeral 2 denotes a pulse signal generator;
a, 6b are magnetron heater power supplies, 7a, 7b are magnetrons, 9a, 9b are magnetron currents, 20a,
20b is a delay circuit, and 21a and 21b are high voltage power supply units.

In such a configuration, the high voltage power supply 21
a, 21b generate a high voltage of about -4000V and supply the magnetron currents 9a, 9b having an average current of 320 mA to the magnetrons 7a, 7b.

On the other hand, the magnetrons 7a and 7b are one type of electron tubes, and the heaters are preheated by magnetron heater power supplies 6a and 6b, and the high voltage power supply sections 21a and 7b
When a high voltage is applied from the magnetron 21b, the magnetron current 9
a, 9b are supplied and emit microwaves.

The high voltage power supply units 21a and 21b are controlled by a signal from the pulse signal generator 2, and supply the magnetron currents 9a and 9b as pulse currents.

At this time, the pulse frequency is determined in consideration of the stability of the plasma.
0 kHz (repetition time 100-20 μs), pulse
It is considered that the ON time is in the range of about 6 to 12 μs.

When a plurality of magnetrons 7a and 7b are used, the magnetrons 7a and 7b can be used.
7b and slight differences in circuit constants of the high-voltage power supply units 21a and 21b cause slight deviations in the magnitude and pulse timing of the magnetron currents 9a and 9b.

Therefore, at least the magnetron current 9a,
9b, the delay circuit 20a,
20b is used to adjust the pulse timing.

Next, FIG. 5 is a sectional view of the plasma generated by the plasma generator, FIG. 5 (a) shows the plasma state when the discharge is stable, and FIG. 5 (b) shows the plasma state when the discharge is unstable. Is shown.

In FIG. 5, 13 is a plasma generating tube, 2
Reference numeral 2 denotes the generated plasma, and reference numeral 23 denotes a high-brightness discharge concentrated portion.

Here, when the two magnetrons 7a and 7b are operating at the same timing, a uniform discharge as shown in FIG. 5A can be obtained. Although the discharge concentrated portion 23 having a high luminance is formed and the discharge becomes unstable, FIG. 5B corresponds to a state in which the horizontal magnetron 4b oscillates first.

If the magnetron 4a in the vertical direction oscillates first, the plasma is rotated by 90 degrees.

[0031]

That is, in the above-mentioned conventional configuration, the operation timing of the two magnetrons is set to 1 μm.
If the pressure is not kept within the deviation of about s, the generation of plasma becomes unstable, so that the delay circuit needs to adjust the time in units of 0.1 μs.

Therefore, it is considered that there are the following problems. (1) It is actually difficult to match the magnetron currents of the two magnetrons in the first place.

(2) If the value of the magnetron current is changed to control the microwave output, etc., the oscillation threshold of the magnetron changes, and the operation timing of the two magnetrons is shifted. Control over the entire area is practically difficult.

(3) In the case of performing pulse oscillation, a delay circuit for simultaneously oscillating microwaves is required, which makes the control complicated and the control circuit expensive.

(4) Further, particularly when used for exciting a laser oscillator, even if the microwave oscillation timing is shifted by 1 μs, the oscillation efficiency of the laser is reduced by 0.3% and the
If there is a deviation of s or more, stable laser oscillation cannot be obtained.

The present invention solves the above-mentioned conventional problems. A delay circuit is not required, and a single magnetic circuit controls the currents flowing through the respective magnetrons to be equal to each other to stabilize the microwave discharge plasma. It is an object of the present invention to provide a parallel magnetron driving method and a parallel magnetron driving power supply device.

[0037]

In order to achieve the above object, a magnetron drive power supply according to the present invention comprises: a plurality of magnetrons, at least two of which are connected in parallel with each other;
A common power supply unit for supplying current to each of the plurality of magnetrons, and a value of each current so as to reduce a difference between currents supplied to at least magnetrons connected in parallel to each other among the plurality of magnetrons. And a current adjusting means for adjusting the current.

Alternatively, at least one pair of magnetrons connected in parallel to each other, a common power supply unit for supplying current to each of the at least one pair of magnetrons, and reducing a difference between the currents supplied to the at least one pair of magnetrons. And a current adjusting means for adjusting the values of the currents so as to cause the current to flow.

In these cases, the current adjusting means has coils provided respectively corresponding to the magnetrons connected in parallel to each other, and the combined magnetic field generated by the current supplied to the coils becomes zero. It is preferable that the magnetic circuit adjusts a current value flowing through the magnetrons arranged in parallel with each other.

The coils provided for each of the pair of magnetrons connected in parallel may be wound in opposite directions, and may have the same central axis.

Alternatively, a plurality of magnetrons connected to the magnetron drive power supply having the above-described configuration, microwave waveguides connected to the plurality of magnetrons, and a plasma generator provided at an intersection of the microwave waveguides And a tube.

[0042]

According to the above configuration, each current between the magnetrons is:
The timing and the size match each other.

Therefore, the plasma generated by the plasma generator can be stably and uniformly generated temporally and spatially.

[0044]

An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a configuration diagram of a magnetron drive power supply device having a plurality of magnetrons according to the present invention.

In FIG. 1, 1 is a high voltage power supply unit, 2 is a pulse signal generator, 3 is a magnetic circuit, 4a and 4b are coils,
a and 5b are diodes, 6a and 6b are magnetron heater power supplies, 7a and 7b are magnetrons connected in parallel with each other, 8 is a coil midpoint, 9a and 9b magnetron currents, and 10 is a ferrite core for maintaining a magnetic field. The components having the same reference numerals as those in the conventional example have the same contents.

In such a configuration, the high voltage power supply 1
Specifically, it functions as a DC high voltage power supply, but receives a TTL level signal from the pulse signal generator 2 and turns on the DC high voltage by a control element such as a transistor (not shown) built in the high voltage power supply unit 1. / Off, 3-phase 200V
To output a DC high voltage of -5000 V in a pulse form.

The magnetrons 7a and 7b are connected to independent heater power supplies 6a and 6b, respectively, to preheat the heaters.

The coils 4a and 4b of the magnetic circuit are connected to one side of these heaters 7a and 7b, and are connected to the high voltage power supply 1 at the midpoint 8 of the two coils.

On the other hand, the bases of the magnetrons 7a and 7b are common and are connected to the ground of the high voltage power supply unit 1.

Thus, the magnetron currents 9a and 9b are
In synchronism with each other, the coils 4a and 4b pass from the ground of the high-voltage power supply unit 1 through magnetrons 7a and 7b, respectively.
, And flows to the minus high voltage of the high voltage power supply unit 1.

In this embodiment, the magnetron 7a,
Reference numeral 7b denotes an electron tube, which can start oscillating at a high voltage of about 3900 V, and after oscillating, if a voltage change of about several hundred volts is given, the current value changes in a range of 0 to 300 mA.

More specifically, although a magnetron 2M244 manufactured by Matsushita Electric Industrial Co., Ltd. is used, when it is necessary to adjust the current to ± 25 mA at a magnetron current of 200 mA, the magnetron anode voltage is set to 4100 V. It is only necessary to adjust the voltage by ± 30 V, and the anode voltage is adjusted to ± 0.
By changing the magnetron current by 7%, the magnetron current can be changed by ± 12.5%.

Here, the coil 4a and the coil 4b are mounted on the common magnetic circuit 3 so that the magnetic fields cancel each other.

The diodes 5a and 5b are inserted to release a surge current and protect the magnetron.

FIG. 2 specifically shows the magnetic circuit 3, wherein 4a is a coil a, 4b is a coil b, 8 is a coil midpoint, 10 is a ferrite core, and 11 is a bobbin.

In such a configuration, the magnetic circuit 3
Each of the bobbin 11 has 35 covered copper wires having a wire diameter of 0.35 mm.
The coil 4 a and the coil 4 b wound by 0 turns are mounted on the ferrite core 10.

Each of the coils 4a and 4b has a resistance of about 6Ω.
However, even when an average current of 320 mA flows, the loss in the coils 4a and 4b is about 2 W, which is negligible compared to the output 1000 W of the magnetrons 7a and 7b.

The coils 4a and 4b are wound in opposite directions, and the magnetic fields generated by the respective magnetron currents act in the magnetic circuit 3 in opposite directions so as to cancel each other out. In this case, the resultant magnetic field generated is zero.

According to such a configuration, a magnetron current flowing in one magnetron generates a magnetic field in the other coil in the current path, and the magnetic field causes an electromotive force in the other coil placed in the same magnetic circuit. Occurs.

For example, the magnetron currents 9a and 9b flowing through the two magnetrons 7a and 7b are in an unbalanced state, and the magnetron current 9a is
b, the magnetron currents 9a and 9b
Magnetic field continues to be generated in the direction corresponding to the coil 4a until the current completely matches, and the generated magnetic field generates an electromotive force in the coil 4b on the smaller current side.

As a result, the magnetron current 9b continues to increase due to the electromotive force. When the magnetic fields generated by the coils 4a and 4b match, the increase in the magnetron current 9b stops, so that the magnetron currents 9a and 9b substantially match, and thereafter the matching state is maintained. become.

Therefore, the combined magnetic field in the magnetic circuit becomes zero when the two magnetron currents completely match, and the operations of the parallel magnetrons are balanced, and the generated plasma can be stabilized temporally and spatially. It becomes possible.

In this embodiment having the above configuration, the timings and current values of the magnetron currents 9a and 9b are as follows.
The pulse frequency was 10 to 100 kHz, and the magnetron currents 9a and 9b matched within the range of 10 to 300 mA, and it was confirmed that the current could be controlled by the magnetic circuit 3.

Further, when the magnetron drive power supply device having the above configuration is applied to a plasma generator or a carbon dioxide laser device, plasma uniformity and stability are superior to conventional microwave discharge excitation, and stable even at high input. The operation can be performed.

In addition, since the oscillation timings of the magnetrons coincided, the load impedance was stabilized, and the impedance matching was facilitated.

Thus, by stabilizing the discharge temporally and spatially, the plasma generation state and the laser mode temporal stability over the conventional DC discharge excitation were obtained.

In the above embodiment, the magnetron has been described by taking a pair of examples connected in parallel. However, the present invention is not limited to this example.

For example, if a plurality of magnetrons are connected in parallel with each other, a configuration having three or more magnetrons is also possible.

Further, in some cases, a pair of magnetrons may be provided which are further branched from a pair connected in parallel and further connected in parallel, and by repeating this, an even number of magnetrons can be controlled.

An odd number of connections, such as providing one magnetron in parallel with a pair connected in parallel, is also possible.
In this case, the current of the odd-numbered magnetron is twice as large as that forming the pair, so that a means for adjusting the output of the magnetron is required.

Further, although the coil is of the axially adjacent type in which the central axes are aligned, it is a matter of course that the coil may be of the radially adjacent type in which the central axes are parallel.

[0073]

The structure of the present invention has the following effects.

(1) Since the magnetic field generated by the current of the magnetron itself is used for controlling the magnetron current, it is possible to control the current with a high degree of consistency for all current values. I do.

(2) An expensive circuit such as a delay circuit is not required and can be manufactured at a low cost. (3) The high-voltage power supply unit can be a single unit having a large electric capacity, and the cost can be reduced.

(4) The discharge plasma is stabilized, and the discharge load impedance can be easily matched. (5) When used as an excitation source of a laser oscillator, laser mode stability is improved.

As described above, the magnetron drive power supply according to the present invention has excellent current controllability despite being inexpensive, and can be widely applied as a drive power supply for a plasma generator. is there.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a parallel magnetron driving method according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a magnetic circuit of the parallel magnetron driving method.

FIG. 3 is a configuration diagram of a plasma generation applicator of the microwave plasma generator.

FIG. 4 is a configuration diagram of a magnetron control circuit of a conventional microwave plasma generator.

FIG. 5 is a cross-sectional view of plasma generated by the plasma generator. (A) A diagram showing a plasma state when discharge is stable. (B) A diagram showing a plasma state when discharge is unstable.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High voltage power supply part 2 Pulse signal generator 3 Magnetic circuit 4a Coil 4b Coil 5a Diode 5b Diode 6a Magnetron heater power supply 6b Magnetron heater power supply 7a Magnetron 7b Magnetron 10 Ferrite core 12a Microwave waveguide 12b Microwave waveguide 13 Dielectric plasma Generator tube 14a Load impedance matching device 14b Load impedance matching device 15a Directional coupler 15b Directional coupler 16a Reflecting end 16b Reflecting end 17a Standing wave of microwave 17b Standing wave of microwave 18a Oscillating microwave 18b Oscillating microwave 19a Reflection of microwave 19b Reflection of microwave 20a Delay circuit 20b Delay circuit 22 Plasma 23 Discharge concentrated part with high brightness

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01J 23/34 H05H 1/46

Claims (3)

(57) [Claims] At least two magnetrons are connected in parallel to each other , a power supply unit for supplying current to each of the plurality of magnetrons, and a magnetron connected in parallel to at least one of the plurality of magnetrons. a magnetron drive power supply device and a current adjusting means for adjusting the value of the mutual current to reduce the difference between the supplied current, the current adjustment means connected in parallel with each other magnetron
Having a coil provided corresponding to each of
So that the combined magnetic field generated by the supplied current becomes zero
Flows into the magnetrons arranged in parallel with each other
A magnetron drive power supply that is a magnetic circuit that adjusts the current value . 2. A coil provided corresponding to each of a pair of magnetrons connected in parallel to each other is wound in opposite directions and has the same central axis.
A magnetron drive power supply as described. 3. A plurality of magnetrons connected to the magnetron drive power supply device according to claim 1, a microwave waveguide connected to each of the plurality of magnetrons, and an intersection of the microwave waveguides. A plasma generator having a plasma generating tube provided.