JPH07105537B2 - Plasma equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plasma device that generates plasma by microwave discharge and is used for laser excitation, plasma processing, and the like.

[Conventional technology]

Figure 3 shows the IEEE Journal of Quantum Electronics (IEEE J
ournal of Quantum Electoronics) Vol.QE-18, No. 11 P
It is a schematic sectional drawing which shows the conventional plasma apparatus used for the gas laser apparatus shown by 1839-P1840, in the figure, 1 is a magnetron as a microwave oscillator,
Reference numeral 2 is a waveguide as a microwave circuit for transmitting the microwave generated by the magnetron 1, 21 is the waveguide 2
A quartz laser discharge tube arranged inside, 22 is a laser gas air supply tube communicating with this laser discharge tube 21, 23 is a blower as a gas circulation means provided in the middle of this laser gas air supply tube 22, 24 is the laser A Brewster window that seals both ends of the discharge tube 21, 25 is a total reflection mirror arranged outside the Brewster window 24, 26 is a partial reflection mirror, and 27 is provided at the end of the waveguide 2. High frequency load.

Next, the operation will be described. A laser gas, such as a mixed gas of xenon, hydrogen chloride, and helium, is enclosed in the laser discharge tube 24. On the other hand, the pulsed microwave generated by the magnetron 1 is transmitted to the waveguide 2, and thereby a strong microwave electromagnetic field is generated in the waveguide 2. The laser gas in the laser discharge tube 21 is discharge-disrupted by the strong microwave electromagnetic field to generate plasma, and excimers such as XeCl ^* are generated to obtain a population inversion state. Here, through the Brewster window 24 without light reflection at both ends of the laser discharge tube 21, by forming a laser resonator by the total reflection mirror 25 and the partial reflection mirror 26, the energy of the excimer as laser light. You can take it out. At this time, microwave energy is prevented from being reflected by absorbing extra microwave energy that was not absorbed by the discharge in the high frequency load 27, and the laser discharge tube 22 and the blower 23 are used.
By forcibly circulating the excimer laser gas in 21 at high speed, laser oscillation with a high repetition frequency is performed. Here, since this plasma device uses the closed laser discharge tube 21, when a plasma having conductivity is generated, the microwave mode of the coaxial mode in which the plasma in the laser discharge tube 21 is the inner conductor is generated. The microwave electric field in the plasma becomes dominant and becomes an electric field whose main component is a component parallel to the tube wall of the laser discharge tube 21, so that the plasma is concentrated and generated near the tube wall of the laser discharge tube 21.

[Problems to be solved by the invention]

Since the conventional plasma device is configured as described above, only the microwave of a single frequency by the magnetron 1 can be applied from the microwave oscillation circuit to the waveguide 2 which is a microwave circuit, and various plasmas can be supplied. Not only is not possible to generate, but the node of the discharge in the axial direction of the laser discharge tube 21, which is generated according to the wavelength of the microwave, is fixed, making it difficult to generate uniform plasma in the axial direction. There were problems such as.

The present invention has been made to solve the above problems and enables generation of various plasmas.
An object of the present invention is to obtain a plasma device that can deal with the homogenization of generated plasma in the axial direction.

[Means for solving problems]

In the plasma device according to the present invention, a microwave oscillator for exciting microwaves is formed in a microwave circuit by using a microwave band power transistor.

[Action]

In the plasma device according to the present invention, by forming the microwave oscillator by using the power transistor in the microwave band, it is possible to generate various plasmas by changing the frequency of the generated microwave and to automatically generate the frequency. It is also possible to deal with plasma homogenization in the axial direction by changing the magnetic field.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is a sectional view showing an embodiment in which the plasma device according to the present invention is applied to a gas laser device, and FIG. 2 is an external view thereof. In the figure, 3 is a laser head part having a ridge waveguide type microwave cavity structure, which is a kind of microwave circuit for generating plasma in laser gas by microwave discharge and performing laser excitation. A microwave oscillator 5 configured by using a power transistor in a microwave band and capable of adjusting the frequency of the generated microwave is a laser head unit 3 which outputs the microwave output from the microwave oscillator 4.
A waveguide for guiding to the horn waveguide 6 for expanding the width of the waveguide 5, and 7 for guiding the horn waveguide 6 to the laser head portion 3.
The microwave coupling window 8 is coupled to the laser head 8, and the laser oscillation mirror 8 is attached to the laser head 3. Also, 30
Is a cavity wall following the microwave coupling window 7 in the laser head portion 3, 31 and 32 are ridges provided in the central portion of the cavity wall 30, 33 is a groove formed in one ridge 31, and 34 is It is a conductor wall that constitutes a part of the microwave circuit, and the wall surface of the groove 33 is used in this embodiment. Reference numeral 35 denotes a dielectric provided opposite to the conductor wall 34 and acting as a microwave incident window, for example, a dielectric made of ceramic such as alumina, and 36 is provided by the dielectric 35 covering the groove 33. A discharge space formed between the conductor wall 34 and the dielectric material 35 for enclosing a laser gas, 37 is a ridge 31 having a conductor wall 34 forming a part of a microwave circuit, and a ridge 32 facing it. It is a cooling water channel formed in.

Next, the operation will be described. The microwave generated by the microwave oscillator 4 propagates through the waveguide 5 and the horn waveguide 6
And the impedance is matched by the microwave coupling window 7, so that the microwave is efficiently coupled to the laser head unit 3. The laser head portion 3 has a ridge cavity shape as shown in the drawing, and microwaves are concentrated near the ridges 31 and 32 to generate a very strong microwave electromagnetic field. Due to this strong microwave electromagnetic field, the laser gas sealed in the discharge space 36 is destroyed by discharge, plasma is generated, and the laser medium is excited. At this time, if the microwave oscillator 4 is adjusted and the oscillation frequency of the microwave is appropriately selected,
Various plasmas can be generated corresponding to the frequency.

Here, cooling water is caused to flow through the cooling water passage 37 to cool the discharge plasma, and the laser oscillation conditions are obtained by appropriately selecting the discharge conditions such as the pressure of the laser gas, and the reflecting mirror 8 shown in FIG. Laser oscillation light can be obtained by forming a laser resonator with a reflecting mirror that does not appear in the drawing and is opposed thereto.

At this time, the conductor wall forming part of the microwave circuit
A discharge space 36 is formed between 34 and a dielectric 35 that faces the conductor wall 34 and serves as a microwave entrance window.
In this case, since microwave discharge is performed and microwaves are incident only from one surface of plasma, a phenomenon in which a microwave mode of coaxial mode in which plasma is an inner conductor is dominant occurs. Nothing,
The desired microwave mode discharge can be performed. When the microwave circuit forms a microwave mode having an electric field component perpendicular to the boundary between the dielectric 35 and plasma, like the ridge cavity of the laser head unit 3 shown in the figure, the dielectric 35 and the conductor are Since it faces the wall 34,
An electric field component perpendicular to the conductor wall 34 is also provided, and an electric field penetrating the plasma is created. Therefore, even if a plasma having conductivity is generated, the conductor wall 34 having a conductivity of several orders of magnitude higher than that of the plasma causes the dielectric wall as the microwave entrance window
Since it is arranged opposite to 35, the terminating current of the incident microwave flows through this conductor wall 34, and the electric field near the conductor wall 34 is forced to be perpendicular to the surface of this conductor wall 34. ,
An electric field penetrating the generated plasma is maintained. Therefore, the microwave penetrates into the plasma and a current flows through the plasma, and a spatially uniform plasma is generated due to the continuity of the current.

In the above embodiment, the microwave oscillation frequency is manually set and adjusted, but the microwave oscillation frequency may be automatically changed every moment.
In that case, as the frequency of the microwave changes, the standing wave in the axial direction of the laser head portion 3 generated in the discharge space 36 changes and the position of the node moves, and accordingly, the microwave discharge Since the positions of the nodes also move, a uniform plasma can be obtained in the axial direction.

Further, in the above-described embodiment, the case where the invention is applied to the gas laser device has been described, but it may be applied to a plasma processing device, an ion source, a light source, and the like, and the same effect as that of the above-described embodiment is obtained.

〔The invention's effect〕

As described above, according to the present invention, since the microwave oscillator for exciting the microwave in the microwave circuit is configured by using the power transistor in the microwave band, it is possible to change the oscillation frequency of the generated microwave. Since it is possible to generate various plasmas corresponding to the frequency of microwaves, it is also possible to automatically change the oscillation frequency momentarily, and to achieve uniform plasma in the axial direction. There is an effect that it becomes possible to deal with.

[Brief description of drawings]

FIG. 1 is a sectional view showing a plasma device according to an embodiment of the present invention, FIG. 2 is an external view thereof, and FIG. 3 is a schematic sectional view showing a conventional plasma device. 3 is a microwave circuit (laser head), 4 is a microwave oscillator. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Nishimae 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Sanryu Electric Co., Ltd. Applied Equipment Research Laboratory (72) Inventor Yoshihiro Ueda Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture 8-1, 1-1 Sanryo Electric Co., Ltd. Applied Equipment Research Laboratory

Claims (2)

[Claims] 1. A plasma device for generating plasma by microwave discharge in a microwave circuit, wherein the microwave generated by a microwave oscillator formed by using a microwave band power transistor is provided in the microwave circuit. A plasma device characterized by exciting. 2. The plasma apparatus according to claim 1, wherein the microwave oscillator changes the frequency of the generated microwave with time.