JPS6180880A - Excimer laser device - Google Patents

Abstract

PURPOSE:To realize a high-energy, high-efficiency laser with its laser output efficiency kept not lowered in the presence of an increased input by a method wherein discharge electrodes responsible for laser excitation are approximately square in shape. CONSTITUTION:A pair of discharge electrodes 1, 2 for laser excitation and their discharge surfaces 4 are shaped approximately square. For laser excitation, discharge 3 is produced between the discharge surfaces 4 of the electrodes 1, 2. Formation into a square of a discharge electrode means that it geometrically satisfies Lc(length)approx.=Wc(width), which in turn means, virtually, that discharge input density may be lowered even when the longitudinal dimension is smaller in an excimer laser device. An increased input for discharge will not harm uniformity in the discharge, resulting in a high-energy, high-efficiency laser output.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pulse discharge excited excimer laser.

(Prior Art) An example of a conventional excimer laser is shown in FIGS. 8(a) and 8(b). In a conventional excimer laser device, as shown in the figure, discharge electrodes 21 and 22 used for discharge to excite the laser are long and narrow in the optical axis direction 24 of the laser. That is, the relationship between the length Lc and the width Wc shown in the figure is Lc>Wc. Such an excimer laser is introduced in the material MIiV84-28 of the Technical Committee of the Institute of Electronics and Communication Engineers.

(Problem to be solved by the invention) As can be seen from the above structure, in the conventional excimer laser, as the discharge input for laser excitation increases, the laser output increases, but conversely, the efficiency (laser There is a problem that the discharge output/discharge input) decreases.This is because the discharge input density increases due to the increase in the discharge input.
This seems to be because the uniformity of discharge is impaired.

By the way, when the discharge input density is low or low, a method of lengthening Lo can be considered, but in this case, the discharge circuit is likely to become inductive, and it is difficult to obtain a stable discharge due to laser excitation. However, it is disadvantageous in practical use that the excimer laser device is too long in the longitudinal direction.

An object of the present invention is to provide a compact pulse discharge excitation excimer laser device that does not reduce the efficiency of laser output even if the input of discharge for exciting the laser is increased, that is, can obtain high laser output with high efficiency. It is in.

(Means for Solving the Problems) The present invention is a laser discharge excitation excimer laser device characterized in that the shape of the discharge electrode for exciting the laser is approximately square.

(Function/Principle of the Invention) Making the shape of the discharge electrode square is the eighth
Although the electrodes 21 and 21 in the figure are set to Lc and Wc, in reality, even if the length in the longitudinal direction of the excimer laser device is short, the density of the discharge input is reduced, and the discharge input is reduced. Even if the diameter is increased, the uniformity of discharge is not impaired, and a large laser output can be obtained with high efficiency.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention, and FIG. 2 is a plan view showing the discharge surfaces of electrodes 1 and 2 shown in FIG.

In the excimer laser device of the present invention, the shape of the discharge surfaces 4 of the pair of discharge electrodes 1 and 2 for laser excitation is approximately square. A discharge 3 for laser excitation is obtained between the discharge surfaces 4 of the electrodes 1 and 2.

Considering that the number of pre-ionized electrons per unit area (described later) is the same, the length of one side a of the square can be approximately designed as follows depending on the desired laser output energy E0 of the excimer laser device. If the discharge input energy and laser output energy in the conventional example shown in FIG. 8 when the maximum efficiency ηc1 is obtained are Eel and E0°, respectively, the following equations are obtained.

By the way, preliminary ionization is necessary to obtain a stable glow discharge with laser excitation.

Preionization includes X-ray preionization, corona preionization, Uv1 preionization, and electron beam preionization.

In the excimer laser of the present invention, a pre-ionization layer 5 can be provided on the back surface of one of the pair of discharge electrodes, for example, the discharge electrode 1, as shown in FIG. In the case of Figure 3, preliminary ionization 5
X-ray preionization or corona preionization is suitable. In the case of corona pre-ionization, the discharge surface 4 must be made of a metal mesh. Although not shown, the excimer laser of the present invention can also be used in the case where corona and X-ray pre-ionization are installed on the back surfaces of both of the pair of discharge electrodes 1 and 2. As shown in FIG. In the excimer laser, it is also possible to provide pre-ionization 6 on the side surface of the region of radiation t3 in FIG. In this case, electron beam preionization is suitable.

Although the preliminary ionization has been described above, the present invention is not particularly limited to the preliminary ionization.

5 to 7 show examples of resonator configurations used in the excimer laser device of the present invention.

In the case of FIG. 5, the resonator configuration is such that the width of the laser beam 9 is approximately equal to the length a of one side of the square discharge surface 4, and the reflection surface of aX (distance between discharge electrodes 1 and 2) is Two reflecting mirrors are used: a 100% reflecting mirror 7 and an output mirror 8.

Figure 6 shows a 100% reflective mirror 10. The output mirror 11 and two folding mirrors 12 and 13 are used to provide multiple reflections, and a friend resonator is shown. In this case, the laser beam 14 is folded back multiple times within the discharge 3.

In FIG. 7, two resonators made of a pair of the 100% reflecting mirror 7 and the output mirror 8 shown in FIG. 5 are installed on the next side. In other words, in the example shown in Fig. 7, 1 shown in Fig. 5 is used.
Two pairs of resonators are provided: a 100% reflecting mirror 15, an output mirror 17, and a 100% reflecting mirror 16, an output mirror 18 having the same dimensions as the 00% reflecting mirror 7 and the output mirror 8, and the case shown in FIG. 5 is obtained. Laser beams 19 and 20 have the same shape as the laser beam 9 and are orthogonal to each other.

The configuration of the resonator used in the excimer laser device of the present invention is not limited to the examples shown in FIGS. 5 to 7.

(Effects of the Invention) As described above, according to the present invention, a large laser output can be obtained with high efficiency, and since it is square, it can be easily incorporated into equipment, and the effect in actual use is significantly improved. It has the effect of increasing the

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the island shape of the discharge electrode which is the main part of the present invention, Fig. 2 is a plan view of the discharge electrode with a square discharge surface, and Figs. 3 and 4 are the main parts of the discharge electrode suitable for the present invention. Figures 5 to 7 are diagrams showing the structure of a resonator used in the device of the present invention, and Figure 8 (1") is a side view of a conventional electrode, and (B) is a side view of a conventional electrode. It is a front view. 1.2...Discharge electrode, 3...Discharge, 4...Discharge surface, 5.6...Preliminary ionization, 7-10 p 15...1
00chi reflecting mirror, 8, 11, 17, 18...output mirror, 12113...turning mirror, 9t 14t
19... Laser beam Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6

Claims (1)

[Claims] (1) An excimer laser device that excites a laser by pulse discharge, characterized in that the shape of the discharge surface of a discharge electrode for exciting the laser is approximately square.