JP2001274484A - Gas laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas laser device which prevents drop in the output of a laser beam by using a simple constitution with extended life. SOLUTION: In the gas laser device, a laser medium gas is discharge stimulate, and the laser beam is oscillated. A pair of the main discharge electrodes arranged in a laser gas container containing the sealed laser medium gas to stimulate the laser medium gas are provided. A resonance optical system in which a reflecting mirror and an output mirror are faced and arranged by sandwiching the discharge space of the main discharge electrodes is provided. A dust collector which has a dust collecting face close to the optical path of the resonance optical system is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas laser device that excites a gas laser medium by discharge and oscillates a laser beam.

[0002]

2. Description of the Related Art In a gas laser device that oscillates an excimer laser or the like, a high-voltage pulse discharge generated between a pair of main discharge electrodes disposed in a laser gas container excites a gas laser medium sealed in the container to excite the laser. Gain light,
At this time, sputtering or the like occurs at the discharge electrode, thereby generating dust. This dust floats and circulates in the laser gas container in accordance with the gas circulation by the gas circulation fan, causing a decrease in laser light output.
For this reason, a dust collector is provided in the gas circulation path to remove dust floating in the container.

[0003]

However, some dust does not circulate in the laser gas container but flows along the optical axis of the laser light, and adheres to the high-reflection mirror and output mirror constituting the resonance optical system. Resulting in. When dust adheres to these resonance mirrors, unevenness occurs in the pattern of the laser light or the laser output decreases. Further, the mirror absorbs heat due to the laser light and damages the mirror, which causes a shortened life of the laser device.

The present invention has been made in view of the above-mentioned problems of the prior art,
It is an object of the present invention to provide a gas laser device capable of preventing a decrease in output of laser light with a simple configuration and extending the life of the laser device.

[0005]

Means for Solving the Problems In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) In a gas laser device that discharges and excites a laser medium gas to oscillate laser light, a pair of main discharge electrodes arranged in a laser gas container filled with the laser medium gas to excite the laser medium gas, and a reflection mirror A resonant optical system in which the output mirror is disposed to face the discharge space of the main discharge electrode, and a dust collector having a dust collecting surface close to an optical path of the resonant optical system. Features.

(2) In the gas laser device of (1), the dust collector is provided near the reflection mirror or the output mirror.

(3) In the gas laser apparatus of (1), the dust collector has a rectangular shape in which a conductive plate for electrostatic dust collection is arranged on an inner wall and an optical path of the resonance optical system is formed inside the dust collector. It is a dust collector.

(4) In the gas laser apparatus of (1), the dust collector is provided near an output mirror, a conductive plate for electrostatic dust collection is arranged on an inner wall, and the inside of the conductive plate of the resonance optical system is disposed inside. It is a rectangular dust collector in which an optical path is formed.

(5) In the gas laser device of (4), the end of the dust collector has an aperture function for defining the size of the laser beam.

(6) The gas laser device of (1) is an excimer laser oscillation device.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an excimer laser device. The excimer laser device used in this embodiment oscillates an excimer laser (oscillation wavelength: 193 nm) by a laser medium gas in which Ar (argon) gas and F ₂ (fluorine) gas are mixed.

Reference numeral 1 denotes a laser gas container (hereinafter, referred to as a chamber) which is filled and sealed with a laser medium gas. A cooling pipe (not shown) through which cooling water for cooling the inside of the chamber 1 passes is attached to the outer wall of the chamber 1 in close contact with the outer wall by brazing or the like. Further, since the inside of the chamber 1 is filled with fluorine gas, the inner wall of the chamber 1 is subjected to a process for improving corrosion resistance such as forming a passivation with fluorine in advance.

A pair of Ernst-type main discharge electrodes 2a and 2b are provided inside the chamber 1 so as to face each other. The main discharge electrodes 2a and 2b have a semicylindrical shape suitable for performing a uniform glow discharge in the discharge space 20 between the electrodes. A plurality of preliminary ionizing electrodes 3a are provided so as to sandwich the main discharge electrode 2a, and a plurality of preliminary ionizing electrodes 3b are provided so as to sandwich the main discharge electrode 2b. They are arranged facing each other with an interval. The preliminary ionizing electrode 3a is attached to a peaking capacitor through an insulator (not shown). With such a structure, laser oscillation is performed by transverse discharge excitation.

A gas circulation fan 4 for circulating a laser medium gas is provided in the chamber 1, and the fan 4 is rotated by a motor 5, thereby creating a gas flow in the chamber 1. . Also, chamber 1
The main dust collector 6 is installed at the bottom inside. The main dust collector 6 used in the present embodiment collects dust using an electrostatic dust collection method. The position where the main dust collector 6 is installed is in the flow of gas generated by the rotation of the fan 4, and dust such as dust circulating along the flow of gas can be efficiently collected.

At both ends of the chamber 1, main discharge electrodes 2a,
A high-reflection mirror 7 and an output mirror 8 are provided so as to face each other with the discharge space portion 20 between them 2b.
A resonance optical system for oscillating laser light is constituted by these two resonance mirrors. Two dust collectors 9 are disposed between the discharge space 20 and the high reflection mirror 7 and between the discharge space 20 and the output mirror 8 for collecting dust flowing toward the mirror side by electrostatic force. The high-reflection mirror 7 and the output mirror 8 communicate with the space in the chamber 1 via an opening 9a (see FIG. 2) formed in the dust collector 9. The opening 9a cuts the outer periphery of the laser beam and also serves as an aperture for defining the size.

FIG. 2 is a view showing the structure of the dust collector 9. The dust collector 9 uses a conductive plate 10 made of a conductive material and an insulating plate 11 made of a material that does not conduct electricity. As shown in the drawing, two conductive plates 10 forming a pair of a positive electrode and a negative electrode are used. Are vertically arranged in a non-contact manner, and two insulating plates 11 for separating the upper and lower conductive plates 10 are attached so as to sandwich them. In the present embodiment, the conductive plate 10 is made of aluminum, and the insulating plate 11 is made of ceramic.

With such a configuration of the two conductive plates 10 and the two insulating plates 11, a square opening having a rectangular shape through which laser light (light resonated by the high reflection mirror 7 and the output mirror 8) passes. 9a is formed. The diameter of the laser beam output from the output mirror 8 is determined by the shape of the formed opening 9a.
Serves as an aperture. A high-voltage power supply 13 is electrically connected to the pair of conductive plates 10 through a stable resistor 12. By supplying a voltage to the conductive plate 10, the charged dust adheres to the upper and lower conductive plates 10, and a dust collecting operation by an electrostatic dust collecting method is performed. The dust collector 9 is preferably provided on both the high reflection mirror 7 and the output mirror 8 as in the present embodiment in order to reduce dust adhering to the output mirror 8.

Next, the operation of the excimer laser device having the above configuration will be described.

When a voltage is applied to the preliminary ionization electrodes 3a and 3b and the main discharge electrodes 2a and 2b from a high-voltage power supply (not shown) through a capacitor, first, dielectric breakdown occurs between the preliminary ionization electrode 3a and the preliminary ionization electrode 3b. , Spark discharge occurs. Next, ultraviolet light and electrons generated from the spark discharge pre-ionize the laser medium gas, and glow discharge is performed in the discharge space 20 to excite the laser medium gas. The light emitted by the excitation of the laser medium gas is optically resonated between the high reflection mirror 7 and the output mirror 8, and the laser light is output from the output mirror 8 side.

In the process of obtaining a laser beam, the preliminary ionizing electrode 3
While the discharge is repeated between a and 3b and between the main discharge electrodes 2a and 2b, sputtering or the like is generated, the electrode material is worn, and dust is generated. FIG. 3 is a schematic diagram showing the floating and circulating state of dust at this time. A gas flow is generated in the chamber 1 by the gas circulation fan 4 rotated by the motor 5. Most of the generated dust circulates in the chamber 1 along this flow, and is collected by the main dust collector 6 provided in the lower part of the chamber 1.

However, some of the dust does not follow the flow of the gas and tends to flow toward the high-reflection mirror 7 and the output mirror 8 on the side of the resonance mirror. In the case of the conventional device, dust that has entered the aperture located near the resonance mirror is hardly affected by the flow of gas, and is pushed toward the mirror due to the pressure difference generated during discharge. It will adhere to the mirror.

In this embodiment, as shown in FIG. 3, a dust collector 9 serving as an aperture is provided in the vicinity of the high reflection mirror 7, so that it is negatively charged passing through the opening of the dust collector 9. The dust is adsorbed on the positive pole side of the conductive plate 10, and the positively charged dust is adsorbed on the negative pole side of the conductive plate 10, so that dust adhering to the high reflection mirror 7 can be reduced. In addition, since the dust collector 9 having the same function is used on the output mirror 8 side, dust attached to the output mirror 8 can be similarly reduced. Therefore,
It is possible to suppress unevenness of the pattern of the laser light due to dust adhering to the resonance mirror, reduction in output of the laser light, damage to the resonance mirror, and the like.

The arrangement of the dust collector 9 in the chamber 1 is different from that shown in FIG.
The two conductive plates 10 may be positioned at a staggered position. When a vertically long laser beam is obtained, the area where the two conductive plates 10 are positioned in the vertical direction increases the dust adsorption area.

In the above embodiment, an example was shown in which the dust collector 9 was constituted by the two conductive plates 10 and the insulating plate 11, but the configuration of the dust collector 9 is not limited to this. FIG. 4 shows another configuration example of the dust collector 9, and components having the same functions as the components shown in FIG. 2 are denoted by the same reference numerals. The dust collector 9 shown here includes the conductive plate 10 and the insulating plate 11 shown in FIG.
Is divided into a plurality of blocks.
It is configured to be mounted alternately with a stagger of 0 degrees. Thus, a dust collecting effect from up, down, left, and right can be obtained, instead of dust collecting only in the vertical direction as in the dust collector 9 shown in FIG.

FIG. 5 is a view showing still another example of the configuration of the dust collector 9. In the dust collector 9 'shown here, a plurality of plate-shaped conductive plates 10' provided with openings for defining the size of the laser beam are fixed at cylindrical insulating portions 11 ', and the conductive plates 10' Are electrically connected to the stable resistor 12 and the high voltage power supply 13 so that the positive and negative poles alternately become positive and negative. The dust collector 9 'having such a configuration includes
It is possible to collect positively (negatively) charged dust from all the conductive portions 10 'from all directions, up, down, left, and right.

In the dust collectors 9 and 9 'described above, the aperture is formed in a square shape. However, the present invention is not limited to this, and may be, for example, a circular shape. In addition, dust collector 9,
In 9 ', it has an aperture function,
Of course, it may be independent from the aperture.

Further, in this embodiment, an excimer laser device is used, but the present invention is not limited to this.
The present invention can be applied to a gas laser device of a lateral discharge excitation type such as a nitrogen gas laser.

[0029]

As described above, according to the present invention,
It is possible to reduce dust adhering to the resonance mirror with a simple configuration. Accordingly, it is possible to prevent a decrease in the output of the laser light, a pattern unevenness of the laser light, and the like, suppress damage to the resonance mirror, and extend the life of the laser device.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an excimer laser device.

FIG. 2 is a diagram showing a configuration of a dust collector.

FIG. 3 is a diagram illustrating a flow of dust near a high reflection mirror.

FIG. 4 is a view showing one embodiment of a dust collector.

FIG. 5 is a view showing one embodiment of a dust collector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chamber 2a Main discharge electrode 2b Main discharge electrode 3a Pre-ionization electrode 3b Pre-ionization electrode 4 Fan 5 Motor 6 Main dust collector 7 High reflection mirror 8 Output mirror 9 Dust collector 9a Opening 20 Discharge space

Claims (6)

[Claims] 1. A gas laser device which discharges a laser medium gas and oscillates a laser beam by oscillating laser light. A pair of main discharge electrodes arranged in a laser gas container filled with the laser medium gas to excite the laser medium gas, a reflection mirror and An output mirror includes: a resonance optical system disposed so as to face the discharge space portion of the main discharge electrode, and a dust collector having a dust collection surface close to an optical path of the resonance optical system. Gas laser device. 2. The gas laser device according to claim 1, wherein said dust collector is provided near said reflection mirror or output mirror. 3. The gas laser device according to claim 1, wherein a conductive plate for electrostatic dust collection is disposed on an inner wall of the dust collector,
A gas laser device comprising a rectangular dust collector in which an optical path of the resonance optical system is formed. 4. The gas laser device according to claim 1, wherein the dust collector is provided near an output mirror, a conductive plate for electrostatic dust collection is disposed on an inner wall, and an optical path of the resonance optical system is disposed inside the conductive plate. A gas laser device, characterized in that the gas laser device is a rectangular dust collector on which is formed. 5. The gas laser device according to claim 4, wherein the end of the dust collector has an aperture function for defining the size of the laser light. 6. The gas laser device according to claim 1, wherein the gas laser device is an excimer laser oscillation device.