JPH0573072B2 - - 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. Pre-ionization using (UV light), corona, X-rays, etc. is required.

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.

Furthermore, 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, generate a large amount of ionized electrons, and increase laser output.

Means for Solving the Problems The present invention is an excimer laser device in which UV light generated by preliminary discharge is focused on a desired position within the main discharge area using a rotatable mirror surface, and ionization is generated there. be.

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 condensed by a reflecting mirror 9, for example an elliptical mirror, placed behind it and focused on a point 11. The reflecting mirror 9 is an elliptical mirror with a first focal point.
If the second focal point is set at point 11 in the part where UV light 6 is generated, even UV light generated by a small discharge power can be efficiently focused on the main discharge region, and a sufficient amount of ionized electrons can be obtained. By allowing the reflecting mirror 9 to rotate around the support column 10, the focal point 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 pre-ionization electrode 4 and 5 is reflected by a reflecting mirror 9.
The light is focused over the entire length region between the main discharge electrodes 1 and 2. This condensing position is such that the reflecting mirror 9 is placed on the supporting column 1.
By rotating it around 0, it is possible to adjust the light to be focused at an appropriate position where maximum output can be obtained.

FIG. 3 shows an embodiment in which the discharge electrodes 4, 5 for pre-ionization and the reflecting mirror 9 shown in FIG. 1 are arranged symmetrically on both the left and right sides across the main discharge part, and the effect of pre-ionization is even greater. Become. 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 focuses UV light from a preliminary discharge at an appropriate position between the main discharge electrodes of an excimer laser device using a reflecting mirror.
It is possible to promote the pre-ionization effect to perform stable glow discharge, increase the laser output, and reduce the discharge power for pre-ionization.

[Brief explanation of drawings]

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...reflector.

Claims (1)

[Claims] 1. A main discharge electrode and a plurality of preliminary discharge electrodes arranged in the length direction thereof, and ultraviolet light generated by the preliminary discharge is focused between the main discharge electrodes using a reflecting mirror. An excimer laser device featuring: 2. The excimer laser device according to claim 1, wherein the reflecting mirror is an elliptical mirror, the preliminary discharge position is located at the first focal point, and the condensing position is located at the second focal point. 3. The excimer laser device according to claim 1, wherein the reflecting mirror is rotatable about an axis parallel to the length direction of the main discharge electrode. 4. The excimer laser device according to claim 1, wherein the preliminary discharge electrode and the reflecting mirror are arranged symmetrically on both sides of the main discharge electrode.