JPH0479388A - Gas laser equipment - Google Patents

Abstract

PURPOSE:To make it possible to sense surely an output reduction of a gas laser equipment caused from abnormal states such as detuning of an optical resonator and a leakage of a gas laser medium, by sensing the change pattern of the electric energy fed from a power supply to an excitation means, and by deciding the abnormality in the output state of a laser beam. CONSTITUTION:The change pattern of the electric energy fed from a power supply 4 to a discharge excitation part 3 is sensed by a voltage sensor 14 provided in a control means 11. The change pattern of the electric energy sensed by the voltage sensor 14 is processed by a comparator 15 and a decision means 16. Factors of the change pattern of the electric energy are analyzed, and a curve approximate to the change pattern is derived. Then, this curve is compared with the standard curve representing the change pattern of the electric energy in a normal state. Thereby, whether an abnormality is caused in a gas laser equipment 1 or not, is defected and in an abnormal state, laser is stopped from oscillating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a gas laser device that excites a gas laser medium by discharge and outputs laser light.

(Prior art) Various gas laser media are used in gas laser devices, and one of them is Kr, which uses a mixed gas of Ne (neon), Kr (krypton), and F2 (fluorine).
It is known as F excimer laser. When this KrF excimer laser is operated for a long time, the fluorine gas in the gas laser medium dissociates due to the collision of electrons caused by the discharge, and the ratio of the three types of mixed gases deviates from the optimum value. A phenomenon occurs in which the input (input) gradually decreases.

In order to prevent the laser output from decreasing due to such a phenomenon, conventional measures have been taken.

That is, the sensor monitors the output of the laser light output from the gas laser device. If the output of the laser light decreases, the power supply section is controlled to increase the electrical energy to the excitation means for exciting the gas laser medium. This prevents the sensor output from decreasing.

On the other hand, when the electrical energy from the power source reaches the upper limit of the power source itself or the upper limit limited to prevent transition to a discharge or arc state, fresh fluorine gas in the gas laser medium is injected.

When fluorine gas is injected, the mixing ratio of the gas laser medium approaches the initial value and the laser oscillation efficiency is restored to near the initial value, so that the electrical energy supplied to the excitation means can be reduced to about the initial value. In this way, by repeating the increase in electrical energy and the replenishment of fluorine gas, the laser output can be maintained at a predetermined value or higher.

If the laser output does not recover sufficiently even after repeating such operations, the gas laser medium is replaced.

According to such means, when the gas laser medium deteriorates over time and the laser output decreases, it is possible to sufficiently cope with the problem and restore the laser output. However, if an abnormal state occurs in which the laser output decreases due to other causes, such as misalignment of the optical resonator due to vibration or leakage of the gas laser medium, the electrical energy to the excitation means will increase and the fluorine gas Even if the replenishment is repeated, the laser output cannot be restored. So, is it due to a decrease in laser output or deterioration of the gas laser medium over time?
Alternatively, it is necessary to determine whether the problem is caused by an abnormal condition or because it has occurred, and then take appropriate action. However, in the past, since the laser output was simply detected, it was not possible to determine whether or not the above-mentioned abnormal condition had occurred and take appropriate measures.

(Problem to be Solved by the Invention) As described above, in conventional gas laser devices, although it is possible to cope with a decrease in laser output due to deterioration of the gas laser medium over time, it is possible to cope with a decrease in laser output due to deterioration of the gas laser medium over time. If the laser output decreases due to an abnormal condition such as leakage of the gas laser medium, it may not be detected.

This invention was made in view of the above circumstances, and its purpose is to correct the problem when the laser output decreases due to abnormal conditions such as misalignment of the optical resonator or leakage of the gas laser medium. An object of the present invention is to provide a gas laser device that can reliably detect the following.

[Structure of the Invention] (Means and Effects for Solving the Problems) In order to solve the above problems, the present invention provides an airtight container in which a gas laser medium is sealed and is provided with excitation means for exciting the gas laser medium; a supply means for supplying the gas laser medium to the container; a power supply unit that supplies electrical energy to the excitation means to excite the gas laser medium to generate laser light in the airtight container; and one end in the airtight container. an output mirror arranged on one side and forming one of the optical resonators; a high reflection mirror arranged on the other end side and forming the other side of the optical resonator; and a detection means for detecting the output of the laser beam from the output mirror. , a drive control section for controlling electrical energy supplied from the power supply section to the excitation means in accordance with the output of the laser beam detected by the detection means; and an electric energy of the power supply section controlled by the drive control section. and determining means for detecting a fluctuation pattern of the laser beam and determining an abnormality in the output state of the laser beam based on the fluctuation pattern.

According to such a configuration, when the output of the laser beam decreases due to an abnormal condition, the fluctuation pattern of the electric energy supplied to the excitation means also exhibits an abnormal state accordingly, so that the abnormal state is caused by the fluctuation pattern. It is possible to determine that.

(Example) An example of the present invention will be described below with reference to FIG. Reference numeral 1 in FIG. 1 indicates a KrF excimer laser device as a gas laser device according to the present invention, and this gas laser device 1 is equipped with an airtight container 2 in which a gas laser medium is sealed. A discharge excitation section 3 serving as excitation means is provided within the airtight container 2. This discharge excitation section 3 has a main electrode and a preliminary ionization electrode (both not shown), and a power supply section 4 is connected to these electrodes. When electrical energy is supplied from the power source section 4 to the discharge excitation section 3, the discharge excitation section 3 is first pre-ionized by the pre-ionization electrode. When the preliminary ionization progresses sufficiently, a main discharge is generated between the main electrodes, which excites the gas laser medium in the discharge excitation section 3 and generates only laser light.

An output mirror 5 is arranged at one end in the optical axis direction of the discharge excitation section 3, and a high reflection mirror 6 which forms an optical resonator with the output mirror 5 is arranged at the other end. Therefore, the laser light generated in the discharge excitation section 3 is reflected by the output mirror 5 and the high reflection mirror 6 and is amplified.
A part of it is outputted from the output mirror 5.

The output of the laser beam output from the output mirror 5 is detected by the output detector 7. The detection signal from this output detector 7 is amplified by an amplifier 8 and then
The D converter 9 converts the signal into a digital signal. The digital signal from this A/'D converter 9 is input to a drive control section 12 provided in the control device.

A gas supply device 13 is connected to the airtight container 2 via first to third supply lines 14a to 14c. The gas supply device 13 is provided with a neon gas supply source, a krypton gas supply source, and a fluorine gas supply source (not shown). Each of these supply sources is connected to each of the above supply lines 1
It is connected to the airtight container 2 via 4a to 14c. Therefore, neon gas, krypton gas, and fluorine gas can be supplied to the airtight container 2 from the respective supply sources at predetermined ratios.

The power source section 4 connected to the discharge excitation section 3 and each gas supply source of the gas supply device 13 are controlled by a drive control section 12 provided in the control device]1. This drive control section 1
2 receives the digital signal converted by the A/D converter 9. When the output of the laser beam decreases and the digital signal input to the drive control section 12 becomes less than a predetermined value, the drive control section 12 outputs a signal from the power supply section 4.
A control signal is output to increase the supply of electrical energy to the discharge excitation section 3. If the digital signal from the A/D converter 9 does not recover sufficiently even if the electrical energy to the discharge excitation unit 3 is repeatedly increased, or if the output of the laser light does not return to its original state, the drive control unit A control signal is output from 12 to gas supply device 13 . In response to this control signal, fluorine gas is supplied from the fluorine gas supply source to the discharge excitation section 3. As a result, the proportions of each gas component in the gas laser medium are restored, and the laser output can be restored to its original level.

When the laser output is restored by replenishing fluorine gas, A/
Since the digital signal input from the D converter 9 to the drive control section 12 exceeds a predetermined value, the electrical energy supplied from the power supply section 4 to the discharge excitation section 3 decreases.

The fluctuation pattern of the electrical energy supplied from the power source section 4 to the discharge excitation section 3 is detected by the voltage detector 14 provided in the control device.

The fluctuating bump detected by the voltage detector 14 is compared with a plurality of standard patterns by a comparator 15, and a discriminator 16
It is determined by The discrimination result of this discriminator 16 is fed back to the drive control section 12, and the display 1
7 is displayed.

Next, the operation of the gas laser device 1 having the above configuration will be explained. When the gas laser device 1 is operated to output laser light, the output is detected by the output detector 7. The output detected by this output detector 7 is amplified by an amplifier 8, and the A/D
The signal is converted into a digital signal by the converter 9 and inputted to the drive control section 12, where it is compared with a set value. If the digital signal is smaller than the set value, the signal is output to the power supply section 4 and the electric energy for exciting the discharge excitation section 3 is increased.

In this way, the output of the laser beam is constantly detected and compared with the set value by the drive control section 12, and as the output decreases, the electrical energy is increased, and this is repeated.

Even if the electrical energy for exciting the discharge excitation section 3 is increased,
If the output of the laser beam does not increase, a signal is output from the drive control section 12 to the gas supply device 13. As a result, the discharge excitation section 3 is replenished with fluorine scum, and the output is restored.

The repeated state of increase in electrical energy and replenishment of fluorine gas is shown by curves ρ and m in FIG.

The fluctuation pattern of the electrical energy supplied from the power source section 4 to the discharge excitation section 3 is detected by a voltage detector 14 provided in the control device 11. The fluctuation pattern of electrical energy detected by this voltage detector 14 is detected by a comparator 15.
, the processing is performed by the discriminator 16 according to the flowchart shown in FIG. This will be explained below with reference to FIG.

First, when the fluctuation pattern of electrical energy supplied from the power supply unit 4 to the discharge excitation unit 3 is input to the voltage detector IJ,
Since the fluctuation pattern of electrical energy forms a predetermined curve, the curve is transformed into a known function curve (y-a
x' + bx' + cx3 + dx2 + f), its coefficients a to f are determined, and the approximate curve C is set accordingly.

The approximate curve C obtained in step 1 is sequentially compared with a plurality of standard curves S to SN set in the comparator 15 in step 2. These standard curves 81 to SN show various fluctuation patterns of electrical energy under normal conditions, that is, fluctuation patterns under respective conditions in response to deterioration of the gas laser medium over time. If the approximate curve C or the standard curves 81 to SN are approximated, the electric energy fluctuation pattern shown by the approximate curve C is determined to be normal, and a "YES" signal is output. . In other words, the fluctuation pattern of the electrical energy supplied from the power supply section 4 to the discharge excitation section 3 is normal. The variation pattern of electrical energy during normal times is the third
In the figure, ρ and m are shown.

In step 3, it is determined which of the standard curves 81 to SN the approximate curve C determined in step 2 resembles. In step 4, a signal corresponding to the determination result in step 3 is output to the drive control section 12.

The drive control unit 12 uses the power supply unit 4 based on the determination result.
and increases the electrical energy supplied to the discharge excitation unit 3 in accordance with the decrease in the output of laser light. Further, in step 5, the approximate curve C or the similar standard curve S is determined.

-S1 is displayed on the display 17.

On the other hand, if an abnormal condition occurs, such as rubbing of the optical resonator due to vibration, damage to the output mirror 5 or high reflection mirror 6 due to heat from the laser beam, or leakage of the gas laser medium from the airtight container 2,
The electrical energy supplied from the power supply section 4 to the discharge excitation section 3 increases rapidly. This state is shown in FIG. 3n. In such a case, the approximate curve C' approximated from the variation pattern of electrical energy detected by the voltage detector 14 will no longer resemble any of the standard curves 81 to SN. If there are no similar standard curves 81 to SN, the determination result in step 2 is "NO", and the determination result is input to the drive control unit 12 in step 4.Thereby, the drive control unit 12 outputs the power A signal for stopping the section 4 is outputted.The abnormal state is also displayed on the display 17 at step 5.

In this way, the coefficients of the fluctuation pattern of the electrical energy supplied from the power supply section 4 to the discharge excitation section 3 are determined, and the approximate curves C and C- are approximated from the coefficients. A comparison was made with standard curves 81 to SN showing the variation pattern of electrical energy. Therefore, it is possible to detect whether the fluctuation pattern of the electrical energy supplied from the power supply section 4 to the discharge excitation section 3 is normal, that is, whether or not an abnormality has occurred in the gas laser device 1, and to stop laser oscillation in the event of an abnormality.

[Effects of the Invention] As described above, the present invention detects the fluctuation pattern of the electric energy supplied from the power supply section to the discharge excitation section, and determines whether the output state of the laser beam is normal or not based on the fluctuation pattern. I made it possible to distinguish.

Therefore, it is possible to determine whether the problem is in a normal state due to a decrease in the output of the laser beam or deterioration of the gas laser medium over time, or in an abnormal state due to misalignment or damage to the optical resonator or leakage of the gas laser device. Laser oscillation of the gas laser device can be stopped.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a gas laser device showing an embodiment of the present invention, FIG. 2 is a flowchart, and FIG. 3 is an explanatory diagram of a variation pattern of electric energy supplied to a discharge excitation section. 2... Airtight container, 3... Discharge excitation part (excitation means),
5... Output mirror (optical resonator), 6... High reflection mirror (optical resonator), 8... Output detector, 11... Control device, 12... Drive control unit, 13. ...supply device, 1
4''... Voltage detector (discrimination means), 15... Comparator (discrimination means), 16... Discriminator (discrimination means). Applicant's representative Patent attorney Takehiko Suzue No. 3

Claims (1)

[Claims] an airtight container in which a gas laser medium is sealed and provided with excitation means for exciting the gas laser medium; a supply means for supplying the gas laser medium to the airtight container; and supplying electrical energy to the excitation means to excite the gas laser medium. a power supply unit that generates a laser beam in the airtight container;
An output mirror arranged at one end of the airtight container and forming one of the optical resonators, a high reflection mirror arranged at the other end and forming the other of the optical resonators, and output of laser light from the output mirror. a detection means for detecting the excitation means; a drive control section for controlling the electrical energy supplied from the power supply section to the excitation means according to the output of the laser light detected by the detection means; 1. A gas laser device comprising: a determining means for detecting a fluctuation pattern of electric energy of a power supply unit and determining an abnormality in an output state of a laser beam based on the fluctuation pattern.