JPH11121835A - Discharge excitation gas laser device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] The running cost is low, gaseous halides such as CF ₄ having a boiling point close to the boiling point of a laser medium can be removed, and the halogen concentration of a laser gas is reduced even if impurities are removed. To obtain a discharge-excited gas laser device that does not have any. SOLUTION: A gas purification unit 3A has a corona discharge electrode 8 and a collection electrode 9, and applies a voltage obtained by superimposing a negative DC voltage Vd and a pulse voltage Vp to the corona discharge electrode 8. The laser gas 2 in the discharge tube 1 is guided into the gas purification section 3A to be purified. The high-energy electrons generated from the corona discharge electrode 8 by the application of the pulse voltage Vp collide with the gaseous fluoride as the gaseous halide 22 in the laser gas 2 to dissociate into halogen gas and impurities, and return to the original halide. Instead, the impurities present as they are are deposited and removed by the collecting electrode 9. The fine particles 23 in the laser gas 2 are also charged by the electrons, and are deposited and removed by the collecting electrode 9 in the same manner as the impurities described above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge excitation gas laser device such as an excimer laser device, and more particularly to a gas purification technique.

[0002]

2. Description of the Related Art FIG. 7 is a diagram showing the configuration of a conventional discharge-excited gas laser device described in, for example, "Low-Temperature Gas Purification Device for Excimer Laser Technical Data Published by Astec Corporation". In the figure, reference numeral 1 denotes a laser discharge tube, in which a laser gas 2 made of a halogen gas such as fluorine is sealed. Reference numerals 15 and 16 denote a pair of main discharge electrodes disposed to face each other to generate a main discharge for exciting the laser gas 2, and are disposed in the discharge tube 1.
Reference numerals 21a and 21b constitute laser oscillators. Opposite windows 21a and 21b are provided for reflecting laser light and extracting laser light to the outside, and are attached to the discharge tube wall.

Reference numeral 17 denotes a four-terminal circuit for generating a pulse voltage applied to the main discharge electrodes 15 and 16, and power is supplied to the four-terminal circuit 17 from a power supply terminal 19. A switch 18 is turned on when a pulse voltage is generated from the four-terminal circuit 17. Reference numeral 3 denotes a gas purifying apparatus for purifying the laser gas 2 in the discharge tube 1 by a deep cooling separation method. The gas purifier 3 includes a gas purifier 10 having a heat conductor 5 whose bottom is cooled by liquid nitrogen 6, and a particle filter 7 for previously removing fine particles from the laser gas 2 taken into the gas purifier 10. And In this case, the laser gas 2 from the inside of the discharge tube 1 is guided to the particle filter 7 through the conduit 11 to remove the particles, and thereafter the gas purification unit 10
Is taken inside. Then, the laser gas 2 purified by the gas purification unit 10 is returned into the discharge tube 1 through the pipe 12.

Next, the operation of the discharge excitation gas laser device shown in FIG. 7 will be described. By turning on the switch 18,
A pulse voltage is generated from the four-terminal circuit 17, and the pulse voltage is applied between the main discharge electrodes 15 and 16. As a result, a discharge 20 is generated between the main discharge electrodes 15 and 16, the laser gas 2 is excited by the discharge 20, laser oscillation starts, and a laser beam is taken out from one or both of the windows 21 a and 21 b.

Here, as a result of the discharge, the main discharge electrodes 15, 1
6 are sputtered to cause the fine particles 23 and the gaseous halide 22 of the material constituting the electrode to float in the laser gas 2, and the emitted ultraviolet light causes the halide of the constituent material and the adsorbed material to be converted into gas from the discharge tube wall and the insulator. It is released as halides 22 or fine particles 23. These gaseous halides 22 and fine particles 23
This hinders the laser oscillation process, lowers the laser oscillation efficiency, and shortens the life of the laser gas 2. Also fine particles 23
Is attached to the windows 21a, 21b, the windows 21a, 21b
The transmittance of b decreases, and the laser oscillation efficiency decreases.

Therefore, in the discharge excitation gas laser device shown in FIG. 7, the laser gas 2 containing gaseous halide 22 and fine particles 23 generated in the discharge tube 1
Then, the fine particles 23 are removed by being guided to the fine particle filter 7, and thereafter, guided to the inside of the gas purification unit 10 of the gas purification device 3. Even if not described above, the bottom surface 4 of the gas purification unit 10 is a cryogenic surface that has been lowered to the boiling point of the gaseous halide 22 or lower. Therefore, the gaseous halide 2 contained in the laser gas 2 on the bottom surface 4 of the gas purification unit 10
2 is liquefied or solidified and separated from the laser gas 2. Then, the purified laser gas 2 is returned into the discharge tube 1 through the pipe 12.

[0007]

The conventional discharge-excited gas laser apparatus has the above-described structure, and has a problem that the running cost is high since liquid nitrogen is used for cooling. In addition, there is a problem that the removal rate of gaseous halide having a boiling point close to the boiling point of the laser medium, such as CF _4, is poor. Also, in order to remove impurities generated as halides by laser discharge as they are,
There is a problem that the halogen concentration in the gas decreases in accordance with the amount of generated impurities. The present invention has been made in order to solve the above-mentioned problems, and has a low running cost and a CF having a boiling point close to the boiling point of the laser medium.
It is an object of the present invention to provide a discharge-excited gas laser device capable of removing gaseous halides such as _{4 and the} like, and in which the halogen concentration of a laser gas does not decrease even if impurities are removed.

[0008]

According to a first aspect of the present invention, there is provided a discharge excitation gas laser apparatus in which a laser gas as an excitation substance is sealed in a discharge tube, and first and second main discharge electrodes disposed in the discharge tube. In a discharge excitation gas laser device that excites the laser gas by electric discharge during the discharge, a gas purification unit that purifies the laser gas in the discharge tube is provided, and the gas purification unit includes a negative corona discharge electrode and a positive collection electrode. That is, a voltage obtained by superimposing a DC voltage and a pulse voltage is applied between the corona discharge electrode and the collecting electrode.

According to a second aspect of the present invention, there is provided a discharge excitation gas laser apparatus according to the first aspect, wherein the gas purifying section is disposed outside the discharge tube, and guides the laser gas in the discharge tube from the discharge tube to the gas purifying section. And a second conduit for guiding the laser gas purified by the gas purification unit into the discharge tube.

[0010] According to a third aspect of the present invention, in the discharge excitation gas laser device according to the first aspect of the present invention, the gas purifying section is disposed in a discharge tube.

According to a fourth aspect of the present invention, there is provided a discharge excitation gas laser device according to any one of the first to third aspects.
And a pulse voltage generating means for generating a pulse voltage applied between the second main discharge electrode, and a pulse generated by the pulse voltage generating means as a pulse voltage applied between the corona discharge electrode and the collecting electrode. It uses voltage.

According to a fifth aspect of the present invention, there is provided a discharge excitation gas laser apparatus according to any one of the first to third aspects, wherein an auxiliary electrode for generating a corona discharge between the discharge tube and the second main discharge electrode. And a pulse voltage generating means for generating a pulse voltage applied between the second main discharge electrode and the auxiliary electrode, wherein the pulse voltage is applied as a pulse voltage applied between the corona discharge electrode and the collection electrode. The pulse voltage generated by the generating means is used.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. FIG. 1 is a block diagram showing a configuration of a discharge excitation gas laser device according to Embodiment 1 of the present invention. In FIG. 1, parts corresponding to those in FIG. 7 are denoted by the same reference numerals. In the figure, reference numeral 1 denotes a laser discharge tube, in which a laser gas 2 made of a halogen gas such as fluorine is sealed. Reference numerals 15 and 16 denote a pair of main discharge electrodes disposed to face each other to generate a main discharge for exciting the laser gas 2, and are disposed in the discharge tube 1. Reference numerals 21a and 21b constitute laser oscillators. Opposite windows 21a and 21b are provided for reflecting laser light and extracting laser light to the outside, and are attached to the discharge tube wall. Note that a reflection mirror may be used instead of this window.

Reference numeral 17 denotes a four-terminal circuit for pulse generation as a pulse voltage generating means for generating a pulse voltage applied between the main discharge electrodes 15 and 16, and power is supplied to the four-terminal circuit 17 from a power supply terminal 19. Is done. A switch 18 is turned on when a pulse voltage is generated from the four-terminal circuit 17. 3A is a gas purifier for purifying the laser gas 2 in the discharge tube 1. Inside the gas purifying section 3A, a rod-shaped corona discharge electrode 8 for generating corona discharge and a cylindrical collecting electrode 9 for removing impurities are provided.
Is arranged. Here, the laser gas 2 from inside the discharge tube 1 passes through a pipe 11 serving as a first pipe, and the gas purification unit 1
The laser gas 2 which has been taken into 0 and passed through the gas purification unit 10 is returned into the discharge tube 1 through a pipe 12 as a second pipe.

Reference numeral 30 denotes a corona discharge electrode 8 and a collection electrode 9
This is a pulse power supply that generates a pulse voltage Vp to be applied during the period. The pulse voltage Vp generated by the pulse power supply 30 is applied between the corona discharge electrode 8 and the collection electrode 9 via the capacitor 25a of the filter circuit 25.
Reference numeral 24 denotes a DC high-voltage power supply that generates a DC voltage Vd to be applied between the corona discharge electrode 8 and the collection electrode 9.
The DC voltage Vd generated by the DC high-voltage power supply 24 is applied to the corona discharge electrode 8 through the coil 25b of the filter circuit 25.
And between the collecting electrode 9. In this case, a pulse voltage Vp is applied between the corona discharge electrode 8 and the collection electrode 9.
And the DC voltage Vd, and a voltage is applied, and the polarity of the corona discharge electrode 8 is negative.

Next, the operation of the discharge excitation gas laser device shown in FIG. 1 will be described. By turning on the switch 18,
A pulse voltage is generated from the four-terminal circuit 17, and the pulse voltage is applied between the main discharge electrodes 15 and 16. As a result, a discharge 20 is generated between the main discharge electrodes 15 and 16, the laser gas 2 is excited by the discharge 20, laser oscillation starts, and a laser beam is taken out from one or both of the windows 21 a and 21 b.

Here, as a result of the discharge, the main discharge electrodes 15, 1
6 are sputtered to cause the fine particles 23 and the gaseous halide 22 of the material constituting the electrode to float in the laser gas 2, and the emitted ultraviolet light causes the halide of the constituent material and the adsorbed material to be converted into gas from the discharge tube wall and the insulator. It is released as halides 22 or fine particles 23. These gaseous halides 22 and fine particles 23
This hinders the laser oscillation process, lowers the laser oscillation efficiency, and shortens the life of the laser gas 2. When the particles 23 adhere to the windows 21a and 21b, the windows 21a and 21b
The transmittance of 21b decreases, and the laser oscillation efficiency decreases.

Therefore, in the discharge excitation gas laser apparatus shown in FIG. 1, gaseous halides 22 and fine particles 23 generated in the discharge tube 1
1 to the gas purification unit 3A. Since the collecting electrode 9 is grounded, a negative pulse voltage Vp is applied to the corona discharge electrode 8, and as shown in FIG.
More high energy electrons 31 are generated. The high-energy electrons 31 start drifting on the collecting electrode 9 due to the DC electric field between the corona discharge electrode 8 and the collecting electrode 9.

The high energy electrons 31 are supplied to the corona discharge electrode 8
While moving to the collecting electrode 9, the high-energy electrons 31 collide with gaseous fluoride, which is the gaseous halide 22 in the laser gas 2. The gaseous fluoride colliding with the high-energy electrons 31 converts the energy to the high-energy electrons 3
For example, as shown in the equation (1), the impurities (C) 32 and the halogen gas (2F ₂ ) 33 are dissociated.

CF ₄ + e ⁻ → C + 4F * (1)

In the above formula (1), * represents the excited state of the molecule. Some of the impurities 32 dissociated in this way are recombined into the original gaseous fluoride, but the probability of returning to the original molecule is determined by the collision probability. Exists. Since the dissociated impurities 32 exist as fine particles by themselves, they are charged by the electrons 31. Therefore, the impurity 32 starts drifting on the collecting electrode 9 due to the DC electric field, reaches the collecting electrode 9 and is deposited and removed. The fine particles 23 in the laser gas 2 are also charged by the electrons 31, and the impurities 3
As in the case of 2, the particles arrive at the collection electrode 9 and are deposited and removed. The laser gas 2 purified by the gas purification unit 3A is supplied to the pipeline 1
2 and is returned into the discharge tube 1.

According to the discharge-excited gas laser apparatus shown in FIG. 1, the gas purifying section 3A purifies the gas by corona discharge. At the same time, gas halides such as CF ₄ having a boiling point close to the boiling point of the laser medium can be easily removed. Further, the high-energy electrons 31 generated by the corona discharge collide with the gaseous fluoride, which is the gaseous halide 22, and dissociate into the halogen gas 33 and the impurity 32. It is to be deposited and removed by the collecting electrode 9. Therefore, the gaseous halide 22 is not removed as it is by the purification, and the halogen concentration of the laser gas 2 is not reduced by the gas purification.

Embodiment 2 FIG. FIG. 3 is a block diagram showing a configuration of a discharge excitation gas laser device according to Embodiment 2 of the present invention. 3, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG.
1 has a gas purifying section 3A housed in a discharge tube 1, and the other configuration is the same as that of the discharge excitation gas laser device shown in FIG. In this case, a pipe for taking in the laser gas 2 from the inside of the discharge tube 1 into the gas purifying section 3A and a pipe for returning the laser gas 2 purified by the gas purifying section 3A to the inside of the discharge tube 1 become unnecessary. The discharge-excited gas laser device shown in FIG. 3 operates in the same manner as the discharge-excited gas laser device shown in FIG. Further, since the gas purifying section 3A is accommodated in the discharge tube 1, a conduit for connecting the discharge tube 1 and the gas purifying section 3A is not required, so that the configuration can be simplified and the cost can be reduced.

Embodiment 3 FIG. FIG. 4 is a block diagram showing a configuration of a discharge excitation gas laser device according to Embodiment 3 of the present invention. In FIG. 4, portions corresponding to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG.
1 discharges a pulse voltage Vp applied between a corona discharge electrode 8 and a collection electrode 9 constituting a gas purifying section 3A into a dedicated pulse power supply 30 like the discharge excitation gas laser device shown in FIG. Rather than gaining
A pulse generating four-terminal circuit 17 for generating a pulse voltage to be applied between the main discharge electrodes 15 and 16 is obtained. That is, the pulse voltage output from the four-terminal circuit 17 is applied between the main discharge electrodes 15 and 16 and the corona discharge electrodes 8 constituting the gas purifying section 3A.
And between the collecting electrodes 9.

Other configurations of the discharge excitation gas laser device shown in FIG. 4 are the same as those of the discharge excitation gas laser device shown in FIG. In the discharge excitation gas laser device shown in FIG. 4, the pulse voltage Vp from the four-terminal circuit 17 is applied between the corona discharge electrode 8 and the collecting electrode 9 of the gas purification unit 3A. The operation of purifying the laser gas 2 is performed in the same manner as in the discharge excitation gas laser device shown. Therefore, the same effects as those of the discharge excitation gas laser device shown in FIG. 1 can be obtained also in the discharge excitation gas laser device shown in FIG. Also, as a pulse voltage Vp applied between the corona discharge electrode 8 and the collection electrode 9 constituting the gas purification section 3A, the pulse voltage Vp is output from the pulse generating four-terminal circuit 17 to be applied between the main discharge electrodes 15 and 16. Since a pulse voltage is used, a dedicated pulse power supply is not provided, so that the configuration can be made at low cost.

Embodiment 4 FIG. 5 is a block diagram showing a configuration of a discharge excitation gas laser device according to Embodiment 4 of the present invention. In FIG. 5, portions corresponding to those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG.
The discharge excitation gas laser device shown in FIG. 1 has a gas purification unit 3A housed in a discharge tube 1, and the other configuration is the same as that of the discharge excitation gas laser device shown in FIG. In this case, a pipe for taking in the laser gas 2 from the inside of the discharge tube 1 into the gas purifying section 3A and a pipe for returning the laser gas 2 purified by the gas purifying section 3A to the inside of the discharge tube 1 become unnecessary.

The operation of the discharge excitation gas laser apparatus shown in FIG. 5 is similar to that of the discharge excitation gas laser apparatus shown in FIG. Further, since the gas purifying section 3A is accommodated in the discharge tube 1, a conduit for connecting the discharge tube 1 and the gas purifying section 3A is not required, so that the configuration can be simplified and the cost can be reduced.

Embodiment 5 FIG. 6 is a block diagram showing a configuration of a discharge excitation gas laser device according to Embodiment 5 of the present invention. 6, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. 26
Is an auxiliary electrode, which is arranged in the discharge tube 1 in the vicinity of the main discharge electrode 16. 27 is a main discharge electrode 16 and an auxiliary electrode 2
This is a pulse generating four-terminal circuit as a pulse voltage generating means for generating a pulse voltage to be applied during the period 6, and power is supplied from a power terminal 19. This four-terminal circuit 27
Also, similarly to the four-terminal circuit 17, the pulse voltage is generated by turning on the switch 18.

Further, in the discharge excitation gas laser device shown in FIG. 6, the pulse voltage Vp applied between the corona discharge electrode 8 and the collection electrode 9 constituting the gas purification section 3A is changed to the pulse voltage Vp of the discharge excitation gas laser device shown in FIG. Dedicated pulse power source 3
Instead of being obtained from 0, it is obtained from the 4-terminal circuit 27. That is, the pulse voltage output from the four-terminal circuit 27 is applied between the main discharge electrode 16 and the auxiliary electrode 26, and also between the corona discharge electrode 8 and the collection electrode 9 constituting the gas purification unit 3A. Applied. Other configurations of the discharge excitation gas laser device shown in FIG. 6 are the same as those of the discharge excitation gas laser device shown in FIG.

In the discharge excitation gas laser device shown in FIG. 6, a pulse voltage is generated from the four-terminal circuit 17 by turning on the switch 18, and this pulse voltage is applied between the main discharge electrodes 15 and 16. Discharge 20 occurs.
Similarly, when the switch 18 is turned on, a pulse voltage is generated from the four-terminal circuit 27, and the pulse voltage is applied between the main discharge electrode 16 and the auxiliary electrode 17 to generate corona discharge. Then, the laser gas 2 is excited by these discharges, laser oscillation starts, and laser light is extracted outside from one or both of the windows 21a and 21b. Further, the pulse voltage Vp from the four-terminal circuit 27 is applied between the corona discharge electrode 8 and the collecting electrode 9 of the gas purifying unit 3A, and in the gas purifying unit 3A, as in the discharge excitation gas laser device shown in FIG. The operation of purifying the laser gas 2 is performed.

According to the discharge-excited gas laser device shown in FIG. 6, the same operation and effects as those of the discharge-excited gas laser device shown in FIG. 1 can be obtained, and the corona discharge electrode 8 and the trapping electrode constituting the gas purifying section 3A can be obtained. The main discharge electrode 16 and the auxiliary electrode 17 are used as a pulse voltage Vp applied between the collector electrodes 9.
Since the pulse voltage output from the pulse generating four-terminal circuit 27 is used to apply the pulse voltage during this period, the configuration can be made inexpensively because no dedicated pulse power supply is provided. FIG.
In the discharge excitation gas laser device shown in FIG.
A may be arranged in the discharge tube 1. This eliminates the need for a conduit for connecting the discharge tube 1 and the gas purification unit 3A, thereby simplifying the configuration and making it more inexpensive.

[0032]

According to the first and second aspects of the present invention, gas purification is performed by corona discharge in the gas purification section, which eliminates the need for cooling with liquid nitrogen as in the prior art, and reduces running costs. At the same time, gas halides such as CF ₄ having a boiling point close to the boiling point of the laser medium can be easily removed. Also, high-energy electrons generated by corona discharge collide with gaseous halides to dissociate them into halogen gas and impurities, and impurities that do not return to the original halides are deposited and removed by the collecting electrode, and gas purification is performed. The gas purification does not remove the gaseous halide as it is, and the gas purification does not lower the halogen concentration of the laser gas.

According to the third aspect of the present invention, in the first aspect of the present invention, the gas purifying section is provided in the discharge tube, and a conduit for connecting the discharge tube and the gas purifying section becomes unnecessary. In addition, the configuration becomes simple and the configuration can be made inexpensively.

According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, the first and second pulse voltages applied between the corona discharge electrode and the collection electrode constituting the gas purifying section are used. It utilizes a pulse voltage output from a pulse voltage generating means for generating a pulse voltage applied between the two main discharge electrodes, and can be configured at low cost because no dedicated pulse power supply is provided.

According to a fifth aspect of the present invention, in any one of the first to third aspects of the present invention, the pulse voltage applied between the corona discharge electrode and the collection electrode constituting the gas purifying section is the second main voltage. It utilizes a pulse voltage output from a pulse voltage generating means for generating a pulse voltage applied between a discharge electrode and an auxiliary electrode, and can be configured at a low cost because a dedicated pulse power supply is not provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a discharge excitation gas laser device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a purification operation of a gas purification unit.

FIG. 3 is a configuration diagram of a discharge excitation gas laser device according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a discharge excitation gas laser device according to a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a discharge excitation gas laser device according to a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram of a discharge excitation gas laser device according to a fifth embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional discharge excitation gas laser device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 laser discharge tube, 2 laser gas, 3 A gas purification section, 8 corona discharge electrode, 9 collection electrode, 11 and 12
Conduit, 15, 16 main discharge electrode, 17, 27 4-terminal circuit for pulse generation, 18 switch, 19 power supply terminal, 2
1a, 21b window, 22 gaseous halide, 23
Fine particles, 24 DC high voltage power supply, 25 filter circuit, 2
6 auxiliary electrode, 30 pulse power supply, 31 high energy electron, 32 impurity, 33 halogen gas.

Claims (5)

[Claims] 1. A discharge-excited gas laser device in which a laser gas as an excitation substance is sealed in a discharge tube and which excites the laser gas by a discharge between first and second main discharge electrodes arranged in the discharge tube, A gas purifier for purifying the laser gas in the tube, the gas purifier comprising a negative corona discharge electrode and a positive collector electrode, and a DC voltage applied between the corona discharge electrode and the collector electrode. A discharge excitation gas laser apparatus, wherein a voltage obtained by superposing a pulse voltage and a pulse voltage is applied. 2. The gas purifying section is disposed outside the discharge tube, and a first conduit for guiding the laser gas in the discharge tube from inside the discharge tube to the gas purifying section; The discharge-excited gas laser device according to claim 1, further comprising a second conduit for guiding the laser gas into the discharge tube. 3. The discharge-excited gas laser device according to claim 1, wherein said gas purifier is disposed in said discharge tube. 4. A pulse voltage generating means for generating a pulse voltage applied between the first and second main discharge electrodes, wherein the pulse voltage applied between the corona discharge electrode and the collection electrode is The discharge-excited gas laser device according to any one of claims 1 to 3, wherein a pulse voltage generated by the pulse voltage generating means is used. 5. An auxiliary electrode for generating a corona discharge between the second main discharge electrode and the second main discharge electrode in the discharge tube, and the auxiliary electrode is applied between the second main discharge electrode and the auxiliary electrode. A pulse voltage generating means for generating a pulse voltage, wherein a pulse voltage generated by the pulse voltage generating means is used as a pulse voltage applied between the corona discharge electrode and the collecting electrode. The discharge-excited gas laser device according to any one of claims 1 to 3.