JPS6317579A - Excimer laser device - Google Patents

Abstract

PURPOSE:To make the line of electric force and an equipotential surface roughly intersect orthogonally and to contrive to obtain a uniform electric field by a method wherein the equipotential surface is formed within the surface of a lattice-type electrode at the time of discharge by providing the lattice-type electrode within the plane roughly intersecting orthogonally to the electric field direction between a pair of main discharge electrodes. CONSTITUTION:The capacitances of peaking capacitors 5 and 6 and made equal, the capacitance of peaking capacitors 11 and 12 are made equal, and a lattice-type electrode 13 is provided within the plane at an equal distance from both main discharge electrodes 1 and 2. Therefore, the lattice-type electrode 13 always holds a potential of 1/2 of the potential difference between the main discharge electrodes 1 and 2, and an equipotential surface is formed within the plane where the lattice-type electrode 13 is positioned, that is, in the plane intersecting orthogonally the electric field direction. Thereby, the strain of the potential surface and the strain of the line of electric force are corrected, the potential surface and the line of electric force roughly intersect orthogonally and a laser, which has a broad beam section intensity distribution in the direction parallel to the main discharge electrodes as well and has a good spacious uniformity, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an excimer laser device that obtains laser oscillation by discharging between at least a pair of main discharge electrodes.
In particular, it has been improved to evenly distribute the lines of electric force between both electrodes.

B. Prior Art The electrodes of a conventional excimer laser device are constructed as shown in FIG. A pair of opposing main discharge electrodes 1 and 2 extend in the direction perpendicular to the plane of the paper (hereinafter referred to as the longitudinal direction).
, 2 are applied with a high voltage at predetermined intervals via terminals 3 and 4 from a high voltage control circuit (not shown). On both sides of the base of one main discharge electrode 2, a plurality of rows of peaking capacitors 5 and 6 are provided in the longitudinal direction, one electrode of the peaking capacitors 5 and 6 is grounded, and the other electrode is connected to the The preionization electrodes 7, 8 and 9, 10 are connected to the terminal 3 via the spark gap G of the preionization electrodes 7, 8 and 9, 10 arranged with a gap therebetween.

When a high voltage is applied to the terminals 3, 4, a spark discharge occurs in the spark gap G, thereby charging the peaking capacitor 5.6. Ultraviolet rays are generated by the spark discharge, and the laser gas between the main discharge electrodes 1 and 2 is preliminarily ionized to increase the electron density. As a result, the laser gas impedance between the main discharge electrodes decreases, so the peaking capacitor 5
, 6 reaches the breakdown voltage of the laser gas, the charges in the peaking capacitors 5 and 6 are discharged between the main discharge electrodes 1 and 2, and the laser gas is excited to cause laser oscillation.

Problems to be Solved by the C0 Invention In order to increase the cross-sectional pattern of the laser beam obtained with the above-mentioned excimer laser device and make it spatially uniform, Uniformly ionize the laser gas in the area.

■ Make the electric field between the main discharge electrodes 1 and 2 uniform.

is required.

However, the spark discharge generated in the spark gap G of the pre-ionization electrodes 7 to 10 is inherently an unstable discharge, and the amount of ultraviolet light generated is not constant, making it difficult to uniformly ionize the laser gas. In addition, in order to obtain a uniform electric field, it is necessary to increase the width and thickness of the main discharge electrode, and ideally the discharge surfaces of the main discharge electrodes 1 and 2 should have a large curvature, as shown by the broken line in Figure 4. However, in practice, both ends are rounded with a relatively small curvature, as shown by the solid line, in order to make the device more compact. Therefore, an electric field having desired uniformity cannot be obtained. Further, the pre-ionization electrodes 7 to 10 arranged near the main discharge region cause disturbance of the electric field distribution determined by the shape of the main discharge electrodes 1 and 2.

As described above, in the conventional excimer laser device, it was difficult to generate a uniform discharge over a wide area, so the resulting laser beam cross-sectional shape was small and had poor spatial uniformity.

An object of the present invention is to provide an excimer laser device that solves the above-mentioned problems by distributing lines of electric force between main discharge electrodes at equal intervals and by making the potential surfaces also at equal intervals.

Means for Solving Problem D1 The above problem is solved by arranging the grid electrode 13 in a plane substantially perpendicular to the electric field direction between the pair of main discharge electrodes 1 and 2.

During the 81 action discharge, an equipotential surface is formed within the plane of the grid electrode 13, and the lines of electric force and the potential surface are substantially perpendicular to each other, resulting in a uniform electric field.

F. Embodiment FIG. 1 shows an embodiment of the present invention, and parts similar to those in FIG. 3 are given the same reference numerals and will be described below.

In this embodiment, peaking capacitors are attached to both of the pair of main discharge electrodes 1 and 2.

That is, rows of peaking capacitors 5 and 6 are provided on both sides of the base of the main discharge electrode 2 as in FIG. 3.

Similarly, rows of peaking capacitors 11 and 12 are provided on both sides of the base of the main discharge electrode 1. The capacitances of the four peaking capacitors shown are the same. Peaking capacitors 11 and 5 are connected in series between terminals 3 and 4 via pre-ionization electrodes 7 and 8, and peaking capacitor 6 is connected between terminals 3 and 4.
and 12 are preionization electrodes 9. and 12, respectively. They are connected in series via IO. Here, the spark gap G1 between the pre-ionization electrodes 7 and 8 and the spark gap G2 between the pre-ionization electrodes 9 and 10 are arranged point-symmetrically with respect to the center X between the main discharge electrodes 1 and 2, as shown in the figure. be done. Further, a grid electrode 13 is arranged in a plane passing through the center
and the pre-ionization electrode 10.

The operation of this excimer laser device will be explained.

When a high voltage is applied to terminals 3 and 4, spark discharge occurs in spark gaps Gl and G2, which have a gap of several I, and terminals 3 and 4
Current flows between peaking capacitors 5.6.11.
12 is charged. At this time, the ultraviolet rays generated by the spark discharge preliminarily ionize the laser gas between the main discharge electrodes 1 and 2, thereby lowering the gas impedance. When each phase of the charging voltage of the peaking capacitors 5, 6 and 11, 12 reaches the breakdown voltage of the laser gas, the charge of each peaking capacitor is discharged between the main discharge electrodes 1, 2. This main discharge excites the laser gas, leading to laser oscillation. Note that a pair of laser mirrors facing each other in the direction perpendicular to the plane of the drawing is omitted.

Now, since the capacitances of the peaking capacitors 5 and 6 and 11 and 12 are set equal, and the grid electrode 13 is provided in a plane equidistant from the amphibious discharge electrodes 1 and 2, the grid electrode 13 is always 172 of the potential difference between main discharge electrodes 1 and 2
, and an equipotential surface is formed in the plane where the grid electrode 13 is located, that is, in the plane perpendicular to the direction of the electric field. Therefore, the distortion of the potential surface and the electric field lines are corrected, and the potential surface and the electric field lines are almost perpendicular to each other. varies spatially,
The problem of the electric field becoming non-uniform, and the problem that a uniform electric field between the main discharge electrodes 1 and 2 can only be obtained in a narrow range due to the roundness of both ends of the main discharge electrodes 1 and 2 are solved. .

In addition, in this embodiment, since each element shown in FIG. 1 is arranged symmetrically with respect to the center X between the main discharge electrodes 1 and 2, the main discharge electrode 1°2 is A more uniform electric field is obtained than if the surrounding elements were arranged asymmetrically.

The intensity distribution of the laser beam cross section obtained by the conventional excimer laser device is shown in Fig. 2 (a) and (b), and the intensity distribution of the laser beam cross section obtained by the excimer laser device of the embodiment shown in Fig. 1 is shown. Figure 2 (C), (
Shown in d). In each figure, the X axis indicates a direction parallel to the main discharge electrodes 1 and 2, the Y axis indicates a direction perpendicular to the main discharge electrodes 1 and 2, and the vertical axis I indicates the light intensity of the laser. As shown in (c), in this example, the intensity distribution in the X-axis direction has a trapezoidal shape compared to the conventional intensity distribution shown in (a), and is closer to the intensity distribution in the Y-axis direction. It can be seen that a laser beam with a wide cross section can be obtained.

In addition, in the embodiment shown in FIG. 1, the resistance is 14°15
By inserting the lattice electrode 1 during laser discharge,
Since no current flows through the pre-ionization electrodes 7 to 10 via the pre-ionization electrodes 3, the input electrical energy is effectively used as discharge necessary for laser oscillation.

Furthermore, if the thickness of the grid electrode 13 is made sufficiently small, the shadow portion of the grid electrode 13 that appears in the cross-sectional intensity distribution of the laser output can be ignored. Furthermore.

If the thickness of the grid lines is made smaller than the gap, the glow discharge generated between the main discharge electrodes 1 and 2 will not be disturbed.

Note that the same effect as described above can be obtained even if the grid electrode 13 is disposed close to either of the main discharge electrodes 1 and 2 in a direction substantially perpendicular to the direction of the electric field.

Alternatively, the grid electrode 13 may be simply installed between the main discharge electrodes 1 and 2 without being connected to the preliminary ionization electrodes 7 to 10.

G1 Effect of the Invention According to the present invention, a uniform electric field can be formed in the main discharge region by providing a grid-like electrode, so that the beam cross-sectional intensity distribution is wide even in the direction parallel to the main discharge electrode, and the beam has good spatial uniformity. Laser is obtained.

As a result, not only is it easier to design an optical system that processes the obtained laser light into a desired shape, but also the volume of the discharge gas is increased, which increases the laser oscillation efficiency and improves the life of the laser gas and the device.

[Brief explanation of drawings]

Figure 1 is a configuration diagram showing one embodiment of the present invention, Figure 2 (a)
- (d) are cross-sectional intensity distribution diagrams of the conventional laser beam device and the example device, respectively. Fig. 3 is a configuration diagram showing an example of a conventional excimer laser device. Fig. 4 explains the cross-sectional shape of the main discharge electrode. It is a diagram. 1.2: Main discharge electrode 5, 6.11.12: Peaking capacitors 7 to 10:
Pre-ionization electrode 13: Grid electrode 14.15: Resistance Gl, G2 Varnish spark gap Patent applicant Nippon Kogaku Kogyo Co., Ltd. Representative patent attorney Fuyuki Nagai Figure 1 (a) (10) 2nd
figure

Claims (1)

[Scope of Claim] In an excimer laser device that obtains laser oscillation by discharge excitation of laser gas between at least a pair of main discharge electrodes, a lattice-shaped electrode is arranged in a plane substantially perpendicular to the direction of an electric field between the pair of main discharge electrodes. An excimer laser device characterized by: