JPH1065243A - Excimer laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excimer laser device, where a discharge electrodes have long service life and ultraviolet rays generated by discharge can be set high in utilization factor. SOLUTION: Dielectric bodies 15 are disposed adjacent to the discharge electrode 8b out of a pair of primary discharge electrodes 8a and 8b, extending in the lengthwise direction of the electrode 8b, and two or more pairs of discharge electrodes 6a and 6b are mounted on the opposite surfaces of the dielectric bodies 15 in the lengthwise direction of the dielectric body respectively. Ultraviolet rays, generated by a discharge which occurs along the surface of the dielectric body 15 between the discharge electrodes 8a and 8b, are made to irradiate laser gas between the primary discharge electrodes 8a and 8b to pre-ionize the laser gas. By doing so, most of the ultraviolet rays generated by discharge can be used for pre-ionizing the laser gas, and by creeping discharge, discharge electrodes can be less sputtered with metal particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excimer laser device, and more particularly to a discharge path for preionization.

[0002]

2. Description of the Related Art FIG. 8 shows a driving circuit of an excimer laser device, wherein 1 is a charging power supply, 2 is a primary-side capacitor charged by a charging power supply 1, and 3 is a discharge composed of a high-speed switching element such as a thyratron. Start switch element, 4
Is the primary side inductance, 5 is the secondary side capacitor, 6
a and 6b are a pair of discharge electrodes, 7 is a secondary side inductance,
8a and 8b are a pair of main discharge electrodes for generating excimer laser light, 9 is a main switch, 10 is a charging resistor, and 11 is a charging inductance.

In the driving circuit configured as described above, when oscillating an excimer laser, first, the main switch 9 is turned on, and the primary side capacitor 2 is charged via the charging inductance 11 and the charging resistor 10. When the discharge start switch 3 is turned on after charging in advance and charging the primary side capacitor 2, the primary side inductance 2, the primary side inductance 4,
The secondary-side capacitor 5 is pulse-charged via the pair of discharge electrodes 6a and 6b.

At the same time as the charging, a pair of discharge electrodes 6a, 6b
Ultraviolet light is generated by the discharge between the electrodes, and the ultraviolet light causes the laser gas between the main discharge electrodes 8a and 8b to be in a weakly ionized state, enabling uniform discharge required for laser oscillation between the main discharge electrodes 8a and 8b. become. When the charge voltage of the secondary capacitor 5 reaches the discharge voltage between the main discharge electrodes 8a and 8b, main discharge is started, and discharge excitation for laser oscillation is performed. Thereafter, the discharge current mainly from the secondary-side capacitor 5 is supplied to the main discharge electrodes 8 a and 8 via the secondary-side inductance 7.
Excitation discharge is maintained by flowing between b. Hereinafter, by repeating this operation, discharge between the main discharge electrodes 8a and 8b is repeatedly excited.

The pair of discharge electrodes 6a and 6b are each formed in a rod shape, and as shown in the perspective view of the electrode portion in FIG. 9, the main discharge electrodes 8a and 6b formed to be elongated in the laser optical axis direction. A plurality of secondary capacitors 5 are connected in series along one or both sides in the longitudinal direction of 8b and arranged in an array. And the secondary capacitor 5
At the time of charging, the discharge electrodes 6a and 6b of each pair perform an air gap arc discharge 12 to generate ultraviolet light 13 to perform preionization of the laser gas between the main discharge electrodes 8a and 8b.

[0006]

However, in the pair of discharge electrodes 6a and 6b performing the air gap arc discharge 12, metal particles are sputtered from the surfaces of the pair of discharge electrodes 6a and 6b during the arc discharge. The metal particles contaminate the laser gas and lower the laser output performance, and the pair of discharge electrodes 6a and 6b themselves are consumed by sputtering, and the life of the pair of discharge electrodes 6a and 6b is 1 to 5 × 10 ⁸ shots. (Shot) is short, and the replacement of the discharge electrode array is required every time the life is shortened.

When air gap arc discharge is performed, ultraviolet light is emitted in all directions, and the ultraviolet light reaching between the main discharge electrodes 8a and 8b is only a part of the generated ultraviolet light. There is a problem that light use efficiency is low.

The present invention has been made in view of the above-mentioned problems, and provides an excimer laser device that can extend the life of a discharge electrode for performing preionization and has high utilization efficiency of ultraviolet light generated by discharge. The purpose is to:

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an excimer laser device which generates a laser beam by exciting a laser gas by a discharge between a pair of main discharge electrodes. And a plurality of pairs arranged along the longitudinal direction and forming a plurality of discharge paths on a surface facing between the pair of main discharge electrodes, and a plurality of pairs discharging to the respective discharge paths of the plurality of discharge paths. An excimer laser device comprising: a discharge electrode; and an ultraviolet light generated by a discharge generated in the discharge path is irradiated to a laser gas between the pair of main discharge electrodes to pre-ionize the laser gas. Is achieved by:

According to the above feature of the present invention, the discharge between the pair of discharge electrodes generated at the time of preliminary ionization occurs only along the surface of the dielectric facing between the pair of main discharge electrodes.
Sputtering of metal particles on the discharge electrode is greatly reduced, and stable irradiation of ultraviolet light is obtained between the pair of main discharge electrodes, whereby the intensity unevenness of the preionization can be reduced.
In addition, most of the ultraviolet light generated by the discharge can be radiated in the direction between the pair of main discharge electrodes, and the utilization efficiency of the ultraviolet light generated by the discharge can be increased.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an excimer laser device according to the present invention will be described below with reference to the drawings. The driving circuit of the excimer laser device is the same as the circuit described with reference to FIG. 8, and the same and corresponding parts are denoted by the same reference numerals throughout the drawings, and redundant description will be omitted.

FIG. 1 is a front view of an electrode portion of an example of an excimer laser device according to the present invention. FIG. 2 is a cross-sectional view of a part of FIG. 1 taken along the line AA. The electrodes, 8a and 8b are a pair of main discharge electrodes, and 15 is a dielectric. The dielectric 15 is formed in a flat plate shape, is disposed along the longitudinal direction near one main discharge electrode 8b, and extends to a position facing between the pair of main discharge electrodes 8a and 8b.

The pair of discharge electrodes 6a and 6b are each formed in a rod shape, and the pair of main discharge electrodes 8a and 8b of the dielectric 15 are formed.
A plurality of them are arranged in contact with the surface of the dielectric body 15 on the side facing therebetween and are arranged at appropriate intervals in the longitudinal direction.

In the excimer laser device configured as described above, when the secondary capacitor 5 is pulse-charged,
A discharge 12 is generated between each pair of discharge electrodes 6a and 6b. The discharge 12 is formed along the surface of the dielectric 15 facing between the pair of main discharge electrodes 8a and 8b. Almost all of the ultraviolet light 13 generated by the discharge 12 irradiates the gas between the pair of main discharge electrodes 8a and 8b to pre-ionize the gas.

FIG. 3 is a front view of an electrode portion of another example of the excimer laser device according to the present invention, and FIG. 4 is a cross-sectional view of a part of BB in FIG. 3, which is different from the above-described example. The point lies in the arrangement and shape of the dielectric. That is, the dielectric 16 of this example has a prismatic shape, and the one main discharge electrode 8b
Are formed along the longitudinal direction in the vicinity of the main discharge electrode 8a which is normally set to the ground potential, and an inclined surface 16a is formed toward the region D above the main discharge electrode 8a.

The pair of discharge electrodes 6a and 6b are each formed in a rod shape, and one of the pair of discharge electrodes 6a is provided on one surface adjacent to the inclined surface 16a of the dielectric 16 and the other is provided on the other surface. The other discharge electrode 6b of the pair is brought into contact with the surface of the dielectric 15 and opposed to each other on the inclined surface 16a, and a plurality of discharge electrodes 6b are attached at appropriate intervals in the longitudinal direction.

In the excimer laser device configured as described above, when the secondary side capacitor 5 is pulse-charged,
A discharge 12 is generated between the pair of discharge electrodes 6a and 6b. This discharge 12 is formed along the surface of the inclined surface 16a toward the region D of the dielectric 16 above the main discharge electrode 8a. Then, most of the ultraviolet light generated by this discharge irradiates the gas in the region D above the main discharge electrode 8a to pre-ionize the gas.

In the case of this example, the discharge surface (16
The position a) is located closer to the main discharge electrode 8b than the position of the discharge surface of the dielectric 15 of the above example, and
The discharge surface (16a) is inclined so as to face a region D above the main discharge electrode 8a.
It is installed nearby. That is, the pair of main discharge electrodes 8
Side surfaces on both sides facing between a and 8b are not covered with the dielectric 16.

This is because the excimer laser device normally oscillates at a high repetition rate.
The laser is oscillated while flowing the laser gas between a and 8b. As shown by the thick arrow in FIG.
The direction is perpendicular to the longitudinal direction of the main discharge electrodes 8a and 8b, so that the laser gas flows smoothly, which is more advantageous than the case of the dielectric 15 of the above-described example. The area where preionization is required is above the main discharge electrode on the ground potential side, and the discharge surface (16
In a), the ultraviolet light generated by the discharge is directed to the area, and the generated ultraviolet light can be effectively used.

In each of the above-described examples, the pair of discharge electrodes 6a and 6b that generate a discharge during preionization are individually formed in a rod shape. However, one of the pair of discharge electrodes 6a and 6b is used as a discharge electrode. 6b (discharge electrode on the side not directly connected to the secondary capacitor 5) may be formed in a rod shape in common. FIG. 5 shows an example in which this example is applied to the other example.
And FIG.

FIG. 5 is a front view of an electrode portion, and FIG. 6 is a cross-sectional view of a part of FIG. 5 taken along the line CC. One discharge electrode 6b of a plurality of pairs is formed in a rectangular rod-shaped electrode 17 in common. Dielectric 16
A plurality of one pair of discharge electrodes 6a are arranged on one surface adjacent to the inclined surface 16a, and the other pair of discharge electrodes 17 are formed on the other surface along the longitudinal direction on the surface of the dielectric material 15. And are mounted facing each other on the inclined surface 16a. When one of the discharge electrodes is shared in this way, the number of components of the discharge electrode can be reduced by half.

FIG. 7 is a front view of a main part showing a modification of the rod-shaped electrode 17 of the embodiment shown in FIGS. 5 and 6. The rod-shaped electrode 18 of this embodiment has an L-shaped overhang portion. An L-shaped overhang 18a is embedded in the dielectric 16. The L-shaped tip portion shortens the distance E of one of the discharge electrodes 6a, that is, is disposed at a position close to the discharge electrode 6a, and the corner portion is positioned at a position close to the inclined surface 16a of the dielectric 16. doing.

As described above, a plurality of pairs of discharge electrodes which generate a discharge at the time of preionization are made common to the dielectric 16
By forming an overhang portion 18a embedded in the inside of the substrate and forming it in a rod shape, and by positioning the end portion thereof at a position close to the inclined surface 16a of the dielectric 16, the electric field strength at the tip portion of the discharge electrode 6a increases, Discharge start is facilitated, and discharge during preionization is ensured.

The dielectric in each example may be formed of plastic, glass, ceramic, or the like, but ceramic is desirable from the viewpoint of halogen gas resistance.

[0025]

As described in detail above, according to the present invention,
Since the discharge between the pair of discharge electrodes generated during the preionization occurs only along the surface of the dielectric facing between the pair of main discharge electrodes, spattering of metal particles on the discharge electrodes is greatly reduced. At the same time, stable irradiation of ultraviolet light can be obtained between the pair of main discharge electrodes, and the intensity unevenness of preliminary ionization can be reduced.

Further, most of the ultraviolet light generated by the discharge is radiated in the direction between the pair of main discharge electrodes.
The utilization efficiency of ultraviolet light generated by the discharge can be increased. Furthermore, the direction of emission of ultraviolet light by discharge for preionization can be controlled by changing the shape, attachment angle, and change of the dielectric.

[Brief description of the drawings]

FIG. 1 is a front view of an electrode section of an example of an excimer laser device according to the present invention.

FIG. 2 is a cross-sectional view of a part of FIG.

FIG. 3 is a front view of an electrode portion of another example of the excimer laser device according to the present invention.

FIG. 4 is a BB cross-sectional view of a part of FIG.

FIG. 5 is a front view of an electrode portion of still another example of the excimer laser device according to the present invention.

6 is a cross-sectional view of a part of FIG. 5 along CC.

FIG. 7 is a front view of a main electrode section showing a modification of the discharge electrode of FIG. 5;

FIG. 8 is a drive circuit diagram of the excimer laser device.

FIG. 9 is a perspective view of an electrode portion of a conventional excimer laser device.

[Explanation of symbols]

 5 Secondary capacitor 6a, 6b, 17, 18 Discharge electrode (for preliminary ionization) 8a, 8b Main discharge electrode 15, 16 Dielectric 12 Discharge 13 Ultraviolet light

Claims (1)

[Claims] 1. An excimer laser device that excites a laser gas by a discharge between a pair of main discharge electrodes to generate a laser beam, wherein the excimer laser device is disposed along a longitudinal direction near one of the pair of main discharge electrodes, A dielectric for forming a plurality of discharge paths on a surface facing between the pair of main discharge electrodes, and a plurality of pairs of discharge electrodes discharging to respective discharge paths of the plurality of discharge paths; An excimer laser device, wherein the laser gas between the pair of main discharge electrodes is irradiated with ultraviolet light generated by the generated discharge to preliminarily ionize the laser gas.