JPH0573073B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an excimer laser device using rare gas halide discharge excitation.

Conventional Technology Excimer lasers are laser devices that emit ultraviolet light, and are expected to find application in semiconductor processing, chemical industry, medical care, energy fields, and other fields.

Eximer lasers have a short laser upper level lifetime of approximately 1 ns, and the stable period of glow discharge is short at most 1000 ns due to the depletion of halogen molecules that contribute to stabilization through the formation of negative ions.
It requires short pulse discharge excitation with a pulse width of 10 ns and a pulse width of 10 ns. However, in such a short period of time, the elementary phenomena required for normal glow discharge formation, such as generation of secondary electrons and avalanche ionization, cannot occur, so ultraviolet light is needed to generate glow discharge. Preliminary ionization is required using (UV light), corona, X-rays, etc.

In the conventional UV light preionization method, a UV light preionization electrode is placed on one side of a main discharge electrode, and a preionization discharge is performed a certain period of time before the main discharge. This method is called a double discharge method because it causes two discharges. Pre-ionization electrodes also include a series type in which creeping discharge occurs in series along an electrode with cuts, and a parallel type in which multi-pins are arranged in parallel.

Problems to be Solved by the Invention In the pre-ionization method, if the amount of pre-ionization is small, the main discharge tends to become an uneven arc, but if it exceeds a certain threshold, a stable glow discharge can be obtained.
The threshold value is said to be approximately 10 ⁵ electrons/cc. However, with conventional methods, a sufficient amount of pre-ionization cannot be obtained.

Further, as mentioned above, since the main discharge is carried out within an extremely short period of several tens of nanoseconds, it is unlikely that electron drift will occur during the discharge. Therefore, it is necessary that the generation of ionized electrons by pre-ionization be performed at the most desirable location for the main discharge. However, in the conventional method, this position can only be optimized by arranging the pre-ionization electrode at best, and sufficient position control cannot be achieved.

The present invention has been made in view of the above points, and an object of the present invention is to promote the pre-ionization effect and generate a large amount of ionized electrons, thereby increasing the laser output.

Means for Solving the Problems The present invention is an excimer that beams the UX light generated by preliminary discharge almost in parallel using a parabolic reflector, passes it into the main discharge region, and generates ionization there. It is a laser device.

Effect According to the above configuration, the
Most of the UV light contributes to ionization in the main discharge region, and even with a small preliminary discharge, a stable glow discharge can be obtained, increasing the excimer laser output.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of an excimer laser device according to the present invention, and FIG. 2 is a sectional view taken along line A-A'. In the figure, a main discharge takes place between main discharge electrodes 1 and 2, producing a glow region 3. On the other hand, pre-ionization occurs between the pre-discharge electrodes 4 and 5, generating UV light 6. Several ten pairs of preliminary discharge electrodes 4 and 5 are provided along the length of the laser tube, and UV light 6 is generated at various locations along the length. 7 and 8 are supports that also serve as leads to the electrodes 4 and 5. The UV light 6 generated by the pre-ionization 6 is converted into a parallel beam 11 by a parabolic reflector 9 installed behind it, and the UV light 6 is converted into a parallel beam 11 by a parabolic reflector 9 installed behind the UV light 6, which is transmitted to a glow region 3 which is the main discharge region between the main discharge electrodes 1 and 2.
pass through. At this time, ionization can be generated in the glow region 3 to generate a large amount of ionized electrons. As a result, stable glow discharge can be obtained and laser output can be increased. If the parabolic reflector 9 is rotatable around the support column 10, the UV light beam 11 can be adjusted to a desired position between the main electrodes 1 and 2. In practice, this amount of rotation may be adjusted experimentally so that the laser output is maximized. 12 is an output coupling mirror, 13 is a total reflection mirror, and 14 is an output beam. Note that actual lasers require other parts and devices such as a vacuum container, blower device, and cooling device, but these are known technologies in the field of excimer lasers and are not essential parts of the present invention. Therefore, illustration is omitted.

In the above configuration, the main discharge is performed over the entire length region between the main discharge electrodes 1 and 2. On the other hand, the UV light 6 generated between each of the pre-ionization electrodes 4 and 5 is turned into a parallel beam 11 by a parabolic reflector 9 and passes through a discharge region spanning the entire length between the main discharge electrodes 1 and 2. This passing position places the parabolic reflector 9 on the supporting column 1.
By rotating it around 0, it can be adjusted to pass through the appropriate position where maximum output is obtained.

FIG. 3 shows an embodiment in which the pre-ionization discharge electrodes 4, 5 and the parabolic reflector 9 shown in FIG. 1 are arranged symmetrically on both the left and right sides with the main discharge section in between.
The effect of pre-ionization becomes even greater. The configuration and operation of each part are essentially the same as those in FIGS. 1 and 2, so the same reference numerals are given and explanations will be omitted.

Effects of the Invention As described above, the present invention allows UV light from a pre-discharge to pass through a parabolic reflector as a parallel beam at an appropriate position between the main discharge electrodes of an excimer laser device, thereby reducing the pre-ionization effect. By promoting stable glow discharge, it is possible to increase the laser output and reduce the pre-ionization discharge power.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts of an embodiment of an excimer laser device according to the present invention, and FIG.
A cross-sectional view taken along the line A' and FIG. 3 are cross-sectional side views of essential parts showing another embodiment of the excimer laser device according to the present invention. 1, 2... Main discharge electrode, 3... Main discharge glow area, 4, 5... Discharge electrode for preliminary ionization, 6... UV
Light, 9... Parabolic reflector, 11... Parallel beam.

Claims (1)

[Claims] 1. A main discharge electrode and a plurality of pre-discharge electrodes arranged in the length direction of the main discharge electrode, ultraviolet light generated by the pre-discharge is converted into a parallel beam by a parabolic reflector, and the main discharge An excimer laser device characterized by passing the laser between electrodes. 2. The excimer laser device according to claim 1, wherein the parabolic reflector is rotatable about an axis parallel to the length direction of the main discharge electrode. 3. Claim 1, in which the preliminary discharge electrode and the parabolic reflector are arranged symmetrically on both sides of the main discharge electrode.
The excimer laser device described in Section 1.