JPS62291188A - Discharge-type laser - Google Patents

Abstract

PURPOSE:To obtain a laser beam whose intensity distributions both in the direction of an electric field and in the direction perpendicular thereto are shaped both in a trapezoid, by dividing at least either of paired main discharge electrodes into two or more in the longitudinal direction thereof. CONSTITUTION:Main discharge electrodes 3 one of which is divided into two in the longitudinal direction are kept at an equal potential and conduct discharge independently with an opposite electrode 2 respectively, and thereby the direction of an electric field in the section of a laser beam presents the shape of a trapezoid. On the other side, the light intensity distribution of the section of the laser beam in the direction of the electrode width perpendicular to the direction of the electric field is a superposition of light intensity distributions having shapes approximate to the shapes of two normal distributions which have peak values at positions corresponding to the central portions 13a and 13b of a discharging surface, and the light intensity distribution as a whole in the direction of the electrode width perpendicular to the direction of the electric field takes the shape of a trapezoid. Thus, the light intensity distributions of a laser beam both in the direction of the electric field and in the direction of the electrode width perpendicular thereto are shaped in a trapezoid.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a discharge type laser, and particularly relates to an improvement of its main discharge electrode.

(Prior Art) In a discharge type laser, as shown in FIG. 4, a pair of rod-shaped main discharge electrodes 2, each having a semicylindrical cross section (see FIG. 3) are placed inside a chamber 1 filled with laser gas. 3
are arranged with a predetermined gap from each other, and the terminals 2a, 3a
By applying a high voltage to the electrodes 2 and 3, a discharge occurs between the electrodes 2 and 3, and the laser gas present there is excited, thereby generating laser light in the longitudinal direction of the electrodes 2 and 3.

In addition, in FIG. 4, 4 indicates a total reflection mirror, and 5 indicates a partial reflection mirror.

In this type of discharge laser, the main discharge electrode 2.3
It is preferable that the electric field distribution between the main discharge electrodes 2 and 3 be uniform, and conventionally, the shapes of the opposing discharge surfaces of the main discharge electrodes 2 and 3 have been devised, and among them, the so-called Chan-type is famous.

(Problems to be Solved by the Invention) Incidentally, an excimer laser is known as one of the discharge type lasers. Even when used, the intensity distribution in the laser beam output is not uniform. That is, as shown in FIG. 5, the in-plane intensity distribution in the electric field direction has a trapezoidal shape, and the intensity distribution in the electrode direction perpendicular to the electric field direction has a shape close to a normal distribution, as shown in FIG.

Therefore, when a laser beam having such an intensity distribution is used as a light source for a uniform irradiation system, there is a problem in that the intensity distribution must be corrected using an optical lens system.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a discharge laser capable of producing a laser beam having a trapezoidal intensity distribution in both the direction of the electric field and the direction perpendicular to the direction of the electric field.

(Means for Solving the Problems) The present invention is such that at least one of a pair of main discharge electrodes is divided into two or more parts in the longitudinal direction, and each part has a normal distribution between it and the opposing electrode. Since the laser oscillates with an intensity distribution having a shape close to , the overall intensity distribution of the laser beam in the electrode direction perpendicular to the electric field direction has a trapezoidal shape similar to the electric field direction.

(Embodiments) Two embodiments of the present invention will be described with reference to FIGS. 1 to 3.

1 and 2 are views corresponding to the A-A cross-sectional view in FIG. 4, respectively, and in the embodiment shown in FIG. 1, one main discharge electrode 3 is divided into two parts 3b, It is divided into 3d. The main discharge electrodes 3b and 3d, which are divided into two, are always kept at the same potential, and each of the main discharge electrodes 3b and 3c is connected to the counter electrode 2.
The electric field direction of the cross section of the laser beam has a trapezoidal shape as shown in FIG. 6, as in the conventional case.

On the other hand, the light intensity distribution of the laser beam cross section in the electrode width direction perpendicular to the electric field direction is as shown in FIG.
, 13c is a superposition of two light intensity distributions having a shape close to a normal distribution shape, with peak values at positions corresponding to 13c, and the overall light intensity distribution in the electrode width direction perpendicular to the electric field direction is as shown in Fig. 7. As shown by the two-dot chain line, it has a trapezoidal shape similar to the direction of the electric field.

Therefore, the light intensity distribution of the laser beam in the electric field direction and the electrode width direction perpendicular to the electric field has a trapezoidal shape, and the laser beam emitted from the excimer laser can be used as a uniform light source without using a correction optical system. Can be done.

In the second embodiment shown in FIG. 2, one main discharge electrode has three parts 23b and 23d along the longitudinal direction.

It is divided into 23f. In this example, the light intensity distribution of the laser beam in the direction perpendicular to the electric field direction is 23a
, 23c, and 23e, the trapezoidal shape is obtained by superimposing three shapes close to normal distributions each having a peak value at a position corresponding to , 23c, and 23e.

In this way, a uniform trapezoidal light intensity distribution can be obtained as a whole, and by dividing one main discharge electrode into multiple parts along the longitudinal direction, the electrode width can be further increased in the electrode width direction of the laser beam. Can be expanded.

(Effects of the Invention) As described above, according to the present invention, one main discharge electrode is divided into a plurality of parts in the longitudinal direction, so that light in the electric field direction of the laser beam cross section and in the electrode width direction perpendicular to the electric field direction is The intensity distribution has a similar trapezoidal shape, and a laser beam with a flat two-dimensional intensity distribution in the cross section of the laser beam over a wide range can be obtained.

Furthermore, since the electrode of the present invention is divided into a plurality of pieces along the longitudinal direction, concentration of discharge current can be avoided.
It can be expected that the discharge volume will expand in the electrode width direction.

Therefore, some types of discharge lasers, such as excimer lasers, which originally could not be used as a light source for a uniform irradiation system, can be used as a uniform irradiation system without optically modifying the emitted laser beam. It can be used as a light source for an irradiation system, and can be used with a simple configuration, for example, as a light source for a semiconductor exposure apparatus. Moreover, if this type of laser is used as a light source of a photo-CVD apparatus, a more uniform thin film can be formed.

Note that although the above explanation uses an excimer laser as an example, lasers other than excimer lasers can also be used for TE discharges in which the light intensity distribution in the electric field direction and the light intensity distribution in the electrode width direction perpendicular to that direction are different. The present invention can also be applied to type lasers.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing main discharge electrodes of two embodiments of the present invention. FIG. 3 is a sectional view showing an example of a main discharge electrode in a conventional excimer laser. FIG. 4 is a schematic configuration diagram showing an example of an excimer laser. FIG. 5 is an electric field direction diagram in the main discharge electrode of FIG. 3. ! FIG. 7 is a diagram showing the light intensity distribution of the laser beam in the electrode direction in the embodiment according to FIG. 1 of the present invention. (Explanation of symbols of main parts) 1... Laser chamber 2.3, 12, 13b, 13d, 23b, 23d. 23f... Main discharge electrodes 2a, 3a... Electrical input terminal 4... Total reflection mirror 5... Output mirror 13a, 13c, 23a, 23c, 23e... Center part of discharge surface FIG. Figure 2 Figure 5 Δμ Width of the electric bed 71'1 Figure 0 Width of the electric bed 71'1 Figure 7

Claims (1)

[Claims] A discharge type laser that generates a laser beam by discharging between at least a pair of main discharge electrodes, characterized in that at least one of the pair of main discharge electrodes is divided into two or more parts in the longitudinal direction. .