JPH0756901B2 - High pressure gas laser device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high pressure gas laser device, and more particularly to an excimer laser device suitable for using a rare gas or a halogen-based gas as a laser medium.

[Conventional technology]

It is generally known that in a high-pressure gas laser device that uses a halogen-based gas, the laser output gradually decreases as the laser oscillation time elapses. It is considered that the main cause of the decrease in laser output is that the halogen-based gas such as HCl or F ₂ that is the laser medium is active, and therefore the discharge electrode reacts with the laser constituent materials such as the gas container and wears out. . As a measure against the decrease in laser output due to these gas deteriorations, conventionally, a method of compensating the output with a power supply system is known. For example, set the initial state to a low charging voltage,
The decrease in output due to gas deterioration is compensated by the increase in charging voltage. Further, a method is adopted in which a decrease in laser output is regarded as a decrease in halogen concentration, halogen injection control is performed, and supply is performed until the laser output is recovered. As an example,
SP I OE / Raise '89 (SPIE
OE / LASE'89, 1989).

[Problems to be Solved by the Invention]

In the above-mentioned prior art, the change in laser output is affected by a decrease in halogen concentration, a change in power supply voltage, and contamination of the laser extraction window. For this reason, since it does not directly correspond to the change in the halogen concentration, the halogen concentration becomes excessive when the halogen is injected. Excessive injection of halogen gas may cause the discharge to proceed in an increasingly unstable direction, which causes a problem that the control system diverges.

An object of the present invention is to provide a high pressure gas laser device capable of detecting a control amount that enables stable operation of the control system itself and stably maintaining a laser output.

[Means for Solving the Problems]

To achieve the above object, in a high-pressure gas laser device including a laser container filled with a high-pressure laser gas containing a halogen-based gas, a second container provided separately from the laser container and communicating with the laser container is installed. A voltage is applied between the discharge electrodes in the container, the discharge voltage at this time,
A high-pressure gas laser device capable of stabilizing a control system by measuring a level change or a pattern of a current, determining a gas state from the result, and detecting a halogen concentration corresponding to the gas state.

[Action]

Since the discharge part in the laser gas containing the halogen gas can be regarded as a kind of impedance, the level of the discharge voltage or current in the second container varies depending on whether the impedance is large or small. When the impedance is low, the halogen concentration is high and the vibration level of the voltage waveform is low. Therefore, by measuring in advance the change in the level of the discharge voltage and the current between the discharge electrodes in the second container, or the amount corresponding to the pattern and the gas state, the measurement or the pattern of the change in the level of the voltage and the current is obtained. It is possible to judge whether the gas state or the discharge form is stable, etc. Thereby, the divergence of the control system and the injection amount of halogen can be appropriately controlled.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, a pair of main discharge electrodes (not shown) are arranged in the laser vessel 1, and a mixed laser gas containing a halogen-based gas serving as a laser medium, such as XeCl, KrF gas and H 2 gas.
It is formed by filling e and Ne. A pipe 2a, a second container 3, a circulation pump 4, and a pipe 2b are connected to one end of the laser container 1 to return to the other end of the laser container 1 to form a closed circuit, and the gas is in a communicating state. In the second container 3, a pair of discharge electrodes 5 are installed insulated. A power supply device 6 is connected to both ends of the discharge electrode 5. An observation window (not shown) is attached to the second container 3 at a position where the space between the discharge electrodes 5 can be observed. One end of the discharge electrode 5 is connected to one end of a capacitor (C) 8 and one end of a high resistance (R) 7, and the other end of the high resistance 7 is connected to one end of a DC power supply 10 via a switch not shown. On the other hand, the other end of the discharge electrode 5 is connected to one end of a capacitor 8 and one end of a DC power supply 10, and a current transformer 9 is connected therebetween. The connection point serves as a ground point and constitutes a circuit of the power supply device 10.

In addition, an ultraviolet light-emitting lamp is provided in the space between the discharge electrodes 5 through an observation window (not shown) attached to the second container 3.
It is configured so that 11 lights 12 can be emitted. In such a configuration, first, the circulation pump 4 is operated to circulate the laser gas in the pipes 2a and 2b and the second container 3 as indicated by arrows.

Then, the voltage of the high-resistance (R) 7 with a time constant of the RC to the capacitor 8 through the V _s is charged by the introduction of a switch (not shown) a voltage V _s of the DC power source 10. The voltage V _s is applied between the discharge electrodes 5, but the discharge electrodes 5
Since the gap length between them has been adjusted in advance so as to withstand pressure, it does not self-destruct. Now, by irradiating the discharge electrode 5 with the light 12 of the ultraviolet light emitting lamp 11, this electrode 5
Since it acts as a preionization and a triggering action between them, the gap between the electrodes is discharged, and the charge of the capacitor 8 flows. Inter-electrode voltage at that time
The waveforms of V _p and current i _p are measured by a voltmeter and current transformer 9 not shown. These measured values have a vibration waveform as shown in FIG. The V _p and i _p change according to the gas state, and the discharge part can be regarded as impedance. Figure 3 summarizes this relationship. That is, when the halogen gas has a low concentration, V _p1 and V _p2 are large and i
_p1 and i _{p2 become} smaller. On the contrary, when the concentration is high, V _p1 and V _p2 are small. In this way, by observing the discharge voltage V _p and the current i _p , the gas state can be judged by comparing the value or pattern with the standard concentration.

Further, since the gap length between the discharge electrodes 5 can be set to be short in a container different from the laser container 1, the power supply voltage can be lowered and the measuring instrument can be made compact. Moreover, since the power supply voltage is low, it does not require an expensive voltage divider and can be used directly as a measurement signal.
There is an effect that there are few erroneous measurements due to noise. In this way, the amount corresponding to the halogen concentration can be ascertained by the gas state without requiring precise or fine adjustment. Therefore, the laser output can be stabilized by combining the means of this device and the gas control system. There is an effect that can be controlled to.
In another embodiment, the same effect can be obtained even if the second container is attached to one end of the laser container.

Although not shown as another embodiment, there is also an effect that the second container can be connected to the upstream side of the gas regenerator to be integrated with the gas regenerator to reduce the size.

〔The invention's effect〕

According to the present invention, the pair of discharge electrodes are housed in the second container, which is separate from the laser container, and the gas state can be determined from the voltage and current waveforms between the discharge electrodes. The injection amount of can be controlled accurately. As a result, the laser output can be stably operated for a long time.

Further, since the gap between the discharge electrodes in the second container can be made small, the applied voltage can be made low, and erroneous measurement due to noise generated by the discharge is small. Further, the power supply device is small and inexpensive.

Then, a constant and stable discharge can be obtained by the trigger action between the discharge electrodes due to the ultraviolet irradiation of the ultraviolet light emitting lamp. Further, except for the measurement, by constantly irradiating the light of the ultraviolet light emitting lamp through the window of the second container, there is an action and an effect of dissociating only a trace amount of hydrogen chloride type impurities.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing discharge voltage and current waveform examples, and FIG. 3 is a diagram showing correspondence between halogen concentration and discharge voltage. 1 ... Laser container, 2a, 2b ... Piping, 3 ... Second container,
4 ... Circulation pump, 5 ... Discharge electrode, 7 ... High resistance, 8
…… Capacitor, 9 …… Current transformer, 10 …… DC power supply, 11…
… An ultraviolet light emitting lamp.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Ogura 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture, Hitachi Research Institute, Ltd. Inside Hitachi Research Laboratory (56) Reference JP-A-2-36580 (JP, A)

Claims (2)

[Claims] 1. A high-pressure gas laser device comprising a laser container filled with a high-pressure laser gas containing a halogen-based gas, the second container accommodating a pair of discharge electrodes provided separately from the laser container and communicating with the laser container. Container of
A power supply device having a means for applying a voltage to the pair of discharge electrodes; and a measuring means for measuring a discharge voltage and a current between the pair of discharge electrodes to determine a gas state in the laser vessel. Characteristic high pressure gas laser device. 2. The high pressure gas laser device according to claim 1, further comprising an ultraviolet light emitting lamp for irradiating ultraviolet light between the pair of discharge electrodes.