JPH05251794A - Excimer laser oscillator - Google Patents

Abstract

PURPOSE:To equalize the quantity of pre-ionization of a rare-gas halide excimer laser oscillator, to stabilize a laser output, particularly a pulse output and improve the deterioration of performance due to the abrasion of an electrode for pre-ionization and to lengthen the lifetime of the electrode. CONSTITUTION:A main discharge electrode and a plurality of oppositely faced pre-ionizing electrode pairs arrayed in the longitudinal direction of the main discharge electrode are mounted. At least one pre-ionizing electrodes 3 (anodes) are formed in ring-shaped electrodes, the others are formed in rod-shaped electrodes 14 (cathodes), and the rod-shaped electrodes are arranged at the central sections of the ring-shaped electrodes, thus conducting pre-ionized discharge along circumferences, then attaining the lengthening of the lifetime of the electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excimer laser device, and more particularly to a preionization electrode for an excimer laser device utilizing rare gas halide discharge excitation.

[0002]

2. Description of the Related Art In recent years, excimer laser oscillators have been rapidly applied to microfabrication as lasers oscillating in the ultraviolet region. In particular, industrialization as a fine processing light source for semiconductors is urgently needed.

The excimer laser has a short laser level lifetime of about 1 ns, and the stable period of glow discharge is as short as 1000 ns due to depletion of halogen molecules that contribute to stabilization by the formation of negative ions. , Short pulse discharge excitation with a rise of about 10 ns and a pulse width of several 10 ns is required.

However, in such a short time, 2
Since various phenomena required for normal normal glow discharge formation, such as generation of secondary electrons and avalanche ionization, cannot occur, in order to perform glow discharge, ultraviolet light (uv
Pre-ionization using light), corona, x-ray, etc. is required.

In the conventional uv photo-preionization method, an uv photo-preionization electrode is arranged on one side of the main discharge electrode, and the pre-ionization discharge is performed for a certain period of time before the main discharge. This method is called a double discharge method because it discharges twice. The pre-ionization electrode also includes a series type in which a creeping discharge is performed in series along a notched electrode and a parallel type in which multi-pins are arranged in parallel.

A conventional technique will be described below with reference to FIG.
FIG. 2 shows an overall schematic configuration diagram of an excimer laser oscillator.

In the laser chamber 1, main electrodes 2 and 3 are arranged to face each other via an insulator, and a main discharge space is formed. With a certain space (insulating space) on the left and right,
A plurality of preliminary ionization electrodes 14 and 15 are arranged along the longitudinal direction of the main discharge electrode via the discharge space (gap).
In the laser operation, a high voltage (HV) is applied to the storage capacitor C ₁ , and the capacitance is transferred to the peaking capacitor C ₂ by closing the switch S. During the transition, the preionization electrode gap breaks down and becomes conductive. Therefore, preionization is performed, and then a reverse voltage is applied between the main discharge electrodes to reach the main discharge, which excites the laser gas to discharge, and optical members (not shown) arranged at both ends in the direction perpendicular to the paper surface. To extract the laser light. Generally, such a system is called an automatic preionization capacity transfer type.

FIG. 3 shows an enlarged view of a pair of opposing preionization electrodes. A gap is provided between the preionization electrodes 14 and 15, but the gap is adjusted to about 0.5 mm to 1 mm as an initial setting, and when the discharge is continued, the gap is gradually consumed and the gap widens.

[0009]

However, as described above, when the gap is widened due to the consumption of the preionization electrode, the laser finally stops. Alternatively, the laser output may become unstable before it is stopped.

According to an experiment conducted by the inventor, the gap was about 2 mm when the laser operation (pulse operation) was about 10 ⁸ shots. This extent of spread does not cause much problem for laser operation, but in some cases, the electrodes facing each other are consumed non-uniformly, the gap becomes non-uniform, and the amount of preliminary ionization becomes non-uniform in location. , The main discharge becomes unstable. As a result, there is a problem that leads to instability of the laser output.

The present invention has been made in view of the above points, and an object thereof is to extend the life of the electrode for preionization.

[0012]

SUMMARY OF THE INVENTION The present invention comprises a main discharge electrode and a pair of opposing preionization electrodes arranged in the lengthwise direction, and one preionization electrode is a ring-shaped electrode. The other preionization electrode is a rod-shaped electrode, and the rod-shaped electrode is arranged substantially in the center of the ring-shaped electrode.

[0013]

According to the above construction, the discharge progresses along the ring-shaped circumference from the portion where the discharge is likely to start, and after the completion of one round, the discharge further progresses to the second round, and the consumption gradually progresses. Therefore, the life of the preionization electrode is extended and the laser output (pulse) is increased.
Improve the stability of.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged view of electrodes for preionization of an excimer laser oscillator according to the present invention. 3 is an anode part of the preionization electrode, and 4 is a cathode part of the preionization electrode. The anode electrode 3 has a ring shape, and the cathode electrode 4 is arranged at the center of the anode electrode. The pair of anode part 3 and cathode part 4 constitutes a preionization electrode.

Therefore, the preionization discharge is applied to the anode part 3
A discharge is generated between the inner peripheral surface of and the outer periphery of the cathode portion 4. When the discharge is continued, the electrodes facing each other are abraded by the spatter and the gaps are opened, so that the gaps in which the discharge is easily started are automatically selected one after another and the discharge is continued.

In FIG. 1, for example, the discharge shifts in the direction of the arrow. Therefore, while the gap is opened in a short time due to the local wear as seen in the conventional electrode, the wear is almost uniform on the circumference by adopting the preionization electrode of the present invention. It can occur and the life of the electrode can be extended.

Since the basic operation of the laser such as the main discharge is the same as that of the conventional example, the description thereof will be omitted.

Further, it is more effective to use a metal material having a small sputtering rate for at least one of the electrodes, particularly the cathode side preionization electrode.

Further, it goes without saying that the ring-shaped anode portion substantially faces the main discharge electrode.

The excimer laser oscillating device according to the present embodiment is particularly effective in terms of laser output stability, not to mention laser output stability.

[0022]

As described above, according to the present embodiment, the cathode side of the opposing preionization electrode is the ring-shaped electrode, the anode side is the rod-shaped electrode, and the anode electrode is arranged at the center of the cathode electrode. As a result, since the discharge is performed along the circumference of the inner surface of the cathode side, the gap does not widen in a short time, the preionization amount becomes uniform, the main discharge becomes stable, and the laser output becomes stable as a result. In addition, the life of the preionization electrode can be extended.

[Brief description of drawings]

FIG. 1 is an enlarged view of a preionization electrode of an excimer laser oscillator according to a first embodiment of the present invention.

FIG. 2 is a schematic overall configuration diagram of a conventional excimer laser oscillator.

FIG. 3 Enlarged view of a conventional excimer laser oscillator preionization electrode

[Explanation of symbols]

 1 Laser Chamber 2 Laser Main Electrode 3 Laser Main Electrode 4 Preionization Electrode 5 Preionization Electrode 14 Preionization Electrode 15 Preionization Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Takahata Kenichi Takahata 3-10-1 Higashisanda, Tama-ku, Kawasaki City, Kanagawa Matsushita Giken Co., Ltd. (72) Masataka Yamazaki 3-chome, Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture No. 10-1 Matsushita Giken Co., Ltd. (72) Inventor Yuji Hashidate 3-10-1 Higashimita, Tama-ku, Kawasaki City, Kanagawa Prefecture Matsushita Giken Co., Ltd.

Claims (3)

[Claims] 1. A main discharge electrode, and a plurality of pairs of opposing preionization electrodes arranged in a lengthwise direction and facing each other. One preionization electrode is a ring-shaped electrode, and the other preionization electrode is rod-shaped. An excimer laser oscillator, wherein the rod-shaped electrode is arranged substantially at the center of the ring-shaped electrode as an electrode. 2. The excimer laser oscillator according to claim 1, wherein at least one of the preionization electrodes is a metal electrode having a small sputtering rate. 3. The pre-ionization electrode of at least one of the electrodes has a ring side facing the main discharge electrode.
The excimer laser oscillator described.