JPH06112566A - Method and device for oscillating pulse gas laser - Google Patents

Abstract

PURPOSE:To eliminate ions between main electrodes generated by discharge so as to stably output pulsed laser light even when a pulse laser is highly repeatedly oscillated. CONSTITUTION:When pulse discharge is generated between main electrodes 6 and 7, a reverse bias control circuit 14 causes a main capacitor 3 charged from a high-voltage power source 1 to discharge by turning on a saturable reactor 11 and turning off another saturable reactor 12 and supplies the discharged charges to the electrodes 6 and 7. As a result, the pulse discharge is generated and a pulse laser outputs pulsed laser light. When the pulse discharge is not generated, on the other hand, the circuit 14 applies a voltage which is opposite in polarity to that of the voltage applied at the time of generating the pulse discharge across the electrodes 6 and 8 from a reverse bias power source 13 by turning off the reactor 12 and turning on the reactor 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse gas laser oscillating device such as an excimer laser which stably outputs a pulse laser at a high repetition rate.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a capacity-shifting pulse gas laser oscillator applied to an excimer laser. The high voltage power supply 1 is connected to a switch 2 such as a thyratron and a main capacitor 3. Of these, the main capacitor 3 is connected to the charging coil 4 and to the pair of main electrodes 6 and 7 arranged in the chamber 5. Further, a preionization electrode 8 composed of a pin electrode and a peaking capacitor 9 are connected to the main electrodes 6 and 7. With such a configuration, the thyratron 2 is in a non-conducting state, and the main capacitor 3 is supplied with power from the high-voltage power supply 1 and charged with the polarity shown in the figure.

When the main capacitor 3 is charged,
When the thyratron 2 becomes conductive, the electric charge stored in the main capacitor 3 is discharged and transferred between the main electrodes 6 and 7. At this time, the charges are also supplied to the preionization electrode 8 to cause preionization by the preionization electrode 8. After that, when the applied voltage between the main electrodes 6 and 7 reaches a predetermined voltage, A main discharge, that is, a pulse discharge is generated between the main electrodes 6 and 7. The voltage waveform applied between the main electrodes 6 and 7 at this time is as shown in FIG. A pulsed laser beam is output by the generation of this pulsed discharge. After that, the main capacitor 3 is charged again, and the discharge thereof causes the output of the pulsed laser light to be repeated.

Excimer lasers are required to have high repetition laser oscillation. Therefore, it is necessary to instantly return the gas state between the main electrodes 6 and 7 after the pulse discharge to the same gas state as before the pulse discharge. Therefore, at present, a fan is driven to circulate gas at high speed, but as the repetition rate becomes higher, it becomes difficult to stably output the pulsed laser light for the following reason.
That is, (1) high-speed gas circulation is required, and the fan and its motor are increased in size.

(2) The gas flow velocity on the surface of each of the main electrodes 6 and 7 is low (the gas flow velocity is "0" at the interface), and the discharge of ions (charged particles) and metastable state atoms generated by pulse discharge. Very high gas flow rates are required to discharge the product. (3) Since the pulse discharge interval becomes short, the residual amount of the above discharge products increases.

Therefore, when a pulse discharge is generated in a state where discharge products are present on the surfaces of the respective main electrodes 6 and 7, hot spots and filamentation (current concentration) occur on the main electrode 6 acting as a cathode. ), Which causes non-uniform pulse discharge, leading to a reduction in pulse laser output. Particularly, in the vicinity of the main electrode 6, a strong electric field is generated due to the space charge, so that the number of generated ions increases and the amount of residual ions increases.

[0007]

When pulsed laser oscillation is performed with high repetition as described above, it becomes difficult to remove discharge products between the main electrodes 6 and 7, and pulsed laser light is output stably. Can not do.

Therefore, the present invention is capable of removing the ions (charged particles) generated by the discharge between the main electrodes and stably outputting the pulsed laser light even if the oscillation of the pulsed laser is highly repeated. It is an object to provide a method and an apparatus thereof.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a pulse gas laser oscillating device for continuously generating a pulse discharge between a pair of main electrodes to output a pulse laser beam. This is a pulsed gas laser oscillation method in which a voltage having a polarity opposite to the polarity for generating is applied between the main electrodes to achieve the above object.

Further, according to the present invention, the main capacitor is charged by the power supplied from the high-voltage power source, the main capacitor is discharged, the charge is supplied to the pair of main electrodes, and pulse discharge is generated between the main electrodes. In a pulsed gas laser oscillator that outputs pulsed laser light by a reverse bias power supply that applies a voltage having a polarity opposite to that of the voltage applied from the main capacitor to each main electrode between the main electrodes, the main capacitor and each main electrode, And a second switch connected between the reverse bias power supply and each of the main electrodes, a first switch closed during pulse discharge and a second switch opened, and during pulse discharge And a reverse bias control circuit that opens the first switch and closes the second switch, thereby achieving the above object.

Further, according to the present invention, the electric power of the high-voltage power supply is supplied through the main capacitor to be charged, and the main capacitor is discharged slowly along with the discharge of the main capacitor, and has a polarity opposite to the voltage polarity applied from the main capacitor to each main electrode. A pulsed gas laser oscillator including a reverse bias application circuit for applying a voltage between main electrodes during pulse discharge, to achieve the above object.

[0012]

By providing such means, during each pulse discharge generated between the pair of main electrodes, a voltage having a polarity opposite to the polarity generating the previous pulse discharge is applied between the main electrodes. . As a result, the ions, which are discharge products on the surface of each main electrode, are removed away from the main electrode surface.

Further, by providing the above-mentioned means, the first reverse bias control circuit is used by the reverse bias control circuit at the time of pulse discharge between the respective main electrodes.
The switch is closed and the second switch is opened, the main capacitor charged by the high voltage power source is discharged, the charge is supplied to the pair of main electrodes, pulse discharge is generated, and pulse laser light is output. On the other hand, during pulse discharge,
The first switch is opened and the second switch is closed by the reverse bias control circuit, and a voltage having a reverse polarity to the voltage polarity applied during pulse discharge is applied to each main electrode from the reverse bias power supply.

By providing the above means, the reverse bias applying circuit is charged through the main capacitor together with the charging of the main capacitor. Then, the discharge of the main capacitor causes a pulse discharge between the main electrodes, and the reverse bias applying circuit discharges slowly with this, and a voltage having a polarity opposite to the voltage polarity applied from the main capacitor to each main electrode is applied to each main electrode. Apply between electrodes.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. The same parts as those in FIG. 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a block diagram of a pulse gas laser oscillator applied to an excimer laser. A thyratron 10 is connected to the high-voltage power supply 1, and the electric charge accumulated in the main capacitor 3 is discharged by the conduction of the thyratron 10. A saturable reactor 11 as a first switch is connected between the main capacitor 3 and the main electrode 6.

Further, a reverse bias power source 13 is connected to each of the main electrodes 6 and 7 via a saturable reactor 12 as a second switch. The output voltage of this reverse bias power supply 13 is from 1/100 to 10 of the output voltage of the high voltage power supply 1.
The positive electrode “+” side is connected to the main electrode 6 and the negative electrode “−” side is connected to the main electrode 7. That is, the reverse bias power supply 13 applies a voltage having a polarity opposite to that of the voltage applied from the main capacitor 3 to the main electrodes 6 and 7 between the main electrodes 6 and 7. On the other hand, the reverse bias control circuit 14 has the following functions. That is, a function of supplying a trigger signal to the grid of the thyratron 10 to conduct the thyratron 10,

When a pulse discharge is generated between the main electrodes 6 and 7, an exciting current is supplied to one saturable reactor 11 to turn it on and the exciting current to the other saturable reactor 12 is stopped. Function to stop the exciting current to one of the saturable reactors 11 to turn it off during the generation of the pulse discharge and supply the exciting current to the other saturable reactor 12 to turn it on. have. Next, the operation of the apparatus configured as described above will be described.

In the initial state before the pulse discharge is generated between the main electrodes 6 and 7, the reverse bias control circuit 14
Supplies an exciting current to one saturable reactor 11 to turn it on, and stops an exciting current to the other saturable reactor 12 to put it off.

The main capacitor 3 is charged by being supplied with electric power from the high voltage power source 1, and the main capacitor 3 is charged even when the supersaturated reactor 11 is off. At this time, as for the polarity of the charging voltage in the main capacitor 3, the high voltage power supply 1 side has a positive electrode “+” and the main electrode 6 side has a negative electrode “−”.

When the reverse bias control circuit 14 supplies a trigger signal to the grid of the thyratron 10, the thyratron 10 becomes conductive and the main capacitor 3
The electric charge stored in is discharged and transferred between the main electrodes 6 and 7.

Due to this transfer of electric charges, electric charges are also supplied to the preionization electrode 8, and preionization occurs in the preionization electrode 8. After that, when the applied voltage between the main electrodes 6 and 7 reaches a predetermined voltage, pulse discharge occurs between the main electrodes 6 and 7. At this time, the polarities of the voltages applied between the main electrodes 6 and 7 are that the main electrode 6 is the negative electrode “−” and the main electrode 7 is the “+”, and the voltage waveform is as shown in FIG. is there. A pulsed laser beam is output by the generation of this pulsed discharge.

After the occurrence of this pulse discharge, the reverse bias control circuit 14 stops the exciting current to one saturable reactor 11 to turn it off, and supplies the exciting current to the other saturable reactor 12 at the same time. Turn on.

When the saturable reactor 12 is turned on, the electric power of the reverse bias power source 13 is supplied between the main electrodes 6 and 7. In this case, the polarities of the voltages supplied between the main electrodes 6 and 7 are such that the main electrode 6 side has a positive electrode “+” and the main electrode 7 side has a negative electrode “−” as shown in FIG. That is, the polarity is opposite to the polarity between the main electrodes 6 and 7 when the pulse discharge is generated. When a voltage of opposite polarity is supplied between the main electrodes 6 and 7 in this manner, the discharge products on the surface of each of the main electrodes 6 and 7 separate from each of the main electrodes 6 and 7 due to the repulsion of the polarity.

That is, when a pulse discharge is generated, as shown in FIG.
As shown in, the negative electrode “−” is applied to the main electrode 6 and the positive electrode “+” is applied to the main electrode 7, and the electrons (−e) are directed from the main electrode 6 to the main electrode 7. In addition, "+" shows a positively charged particle and "-" shows a negatively charged particle.

Next, when the pulse discharge is completed, positive and negative charged particles are removed and the discharge product (neutral product) "m" is also removed by the gas circulation as shown in FIG. However, each positive and negative charged particle on the surface of each main electrode 6, 7 remains as a residual ion.

However, when a voltage having a polarity opposite to that when the pulse discharge is generated is applied to each of the main electrodes 6 and 7, as shown in FIG. The positive and negative charged particles leave their surface and are removed by the gas flow. That is, the gas flow velocity is “0” on the surface of each of the main electrodes 6 and 7, and residual ions are not removed, but these main electrodes 6 and 7 are not removed.
The residual ions are removed because they enter the region where the gas flow velocity is high apart from the surface of 7.

After that, the reverse bias control circuit 14 again
An exciting current is supplied to one saturable reactor 11 to turn it on, and at the same time, an exciting current to the other saturable reactor 12 is stopped to turn it off. By repeating the above operation, pulsed laser light is output at a high repetition rate.

As described above, in the first embodiment, the saturable reactors 11 and 12 are on / off controlled according to the generation of the pulse discharge between the main electrodes 6 and 7, and the pulse is generated during the generation of the pulse discharge. Since a voltage having a polarity opposite to the voltage polarity applied at the time of discharge is applied between the main electrodes 6 and 7, in particular, among the various ions generated by the pulse discharge generation between the main electrodes 6 and 7, Ions on the surface of 7 can be pulled apart and ejected. As a result, it is possible to stably output the pulsed laser light with a high repetition rate without affecting the occurrence of the next pulsed discharge. As a result, a pulse laser with high repetition rate and high average output can be obtained.

In this case, the interval of each pulse discharge occurrence is, for example, 200 μs at a repetition cycle of 5 kHz, which is 2000 times, which is much longer than the pulse width (100 ns) of the pulse discharge, which is sufficient for each pulse discharge occurrence interval. A reverse polarity voltage can be applied.

Further, since the ions are separated from the surface of each of the main electrodes 6 and 7, it is not necessary to increase the gas flow velocity, the fan and its motor can be downsized, and the power consumption thereof can be reduced. Next, a second embodiment of the present invention will be described with reference to the configuration diagram of FIG. The same parts as those in FIG. 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

A reverse bias applying circuit 20 is connected to the high voltage power source 1 via a main capacitor 3. The reverse bias applying circuit 20 is charged by the power of the high-voltage power supply 1 being supplied through the main capacitor 3, and is slowly discharged by conduction of the thyratron 2, and is applied from the main capacitor 3 to each of the main electrodes 6 and 7. It has a function of applying a voltage having a polarity opposite to that of the voltage polarity between the main electrodes 6 and 7.

Specifically, it is composed of a series circuit of a charging coil 21 and a bias capacitor 22. Here, the capacity of the bias capacitor 22 is about 1/10 of the capacity of the main capacitor 3 and the peaking capacitor 9, and the loss becomes large when the capacity is increased.

With such a configuration, the main capacitor 3 is charged with power supplied from the high voltage power supply 1 while the thyratron 2 is in a non-conductive state. At this time, the main capacitor 3
The polarity of the charging voltage at the high voltage power source 1 side is positive "+"
And the main electrode 6 side becomes the negative electrode “−”.

Along with this, the bias capacitor 22
Is the high voltage power supply 1 to the main capacitor 3 and the charging coil 2
It is charged by receiving the power supply through 1. in this case,
Regarding the charging polarity of the bias capacitor 22, the main capacitor 3 side has a positive electrode “+”.

Here, when a trigger signal is supplied to the grid of the thyratron 10 and the thyratron 10 becomes conductive, the electric charge accumulated in the main capacitor 3 is discharged and is transferred between the main electrodes 6 and 7.

Due to the transfer of the charges, the charges are also supplied to the preionization electrode 8 in the same manner as described above, and preionization occurs in the preionization electrode 8. After that, when the applied voltage between the main electrodes 6 and 7 reaches a predetermined voltage, pulse discharge occurs between the main electrodes 6 and 7. The voltage waveform applied between the main electrodes 6 and 7 at this time is as shown in FIG. A pulsed laser beam is output by the generation of this pulsed discharge.

On the other hand, the charge accumulated in the bias capacitor 22 is discharged by the conduction of the thyratron 2, and the charge is supplied between the main electrodes 6 and 7 through the charging coil 21. In this case, the charging coil 21 has a large value (several hundred μ
Since it is set to H), the discharge is performed slowly.

Due to this slow discharge, a voltage having a polarity opposite to that at the time of the occurrence of pulse discharge, that is, a positive electrode “−” is applied to the main electrode 6 side and a negative electrode is applied to the main electrode 7 side between the main electrodes 6 and 7. "-" Is applied. Therefore, after the pulse discharge is generated, as shown in the voltage waveform diagram of FIG. 5, a voltage having the opposite polarity to that at the time of the pulse discharge generation is applied between the main electrodes 6 and 7. As a result, as shown in FIG. 3C, the positive and negative ions on the surfaces of the main electrodes 6 and 7 are separated from the surfaces and are removed by the gas flow.

As described above, in the second embodiment, the same effect as that of the first embodiment can be obtained. In this case, by connecting the reverse bias application circuit 20,
It can be realized with a simple circuit configuration by one high-voltage power supply 1 and one thyratron 2. The present invention is not limited to the above-mentioned embodiments, and may be modified within the scope of the invention.

For example, not only the thyratron 10, but also a gap switch or a semiconductor switch may be used, and the preionization is not limited to the UV spark discharge method using the pin electrode 8, but also the corona method, the X-ray method. A method may be used.

Further, of the respective main electrodes 6 and 7, the polarity "-" is applied to the main electrode 6 and the polarity "+" is not applied to the main electrode 7, but the polarity "+" is applied to the main electrode 6 and the main electrode 7 is reversed. It can also be applied to the case where a polarity "-" is applied.

[0043]

As described above in detail, according to the present invention, even if the oscillation of the pulse laser is highly repeated, the ions generated by the discharge between the main electrodes can be removed, and the pulse laser light can be stably output. It is possible to provide a pulsed gas laser oscillation method and an apparatus therefor.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a pulse gas laser oscillator according to the present invention.

FIG. 2 is a voltage waveform diagram applied between main electrodes in the device.

FIG. 3 is a diagram showing the action of ejecting residual ions by the apparatus.

FIG. 4 is a configuration diagram showing a second embodiment of a pulse gas laser oscillator according to the present invention.

FIG. 5 is a voltage waveform diagram applied between main electrodes in the device.

FIG. 6 is a configuration diagram of a conventional device.

FIG. 7 is a voltage waveform diagram applied between main electrodes in the same device.

[Explanation of symbols]

1 ... High-voltage power supply, 3 ... Main capacitor, 4 ... Charging coil,
5 ... Chamber, 6, 7 ... Main electrode, 8 ... Pre-ionization electrode, 9
... peaking capacitor, 10 ... thyratron, 11,
12 ... Saturable reactor, 13 ... Reverse bias power supply, 14
... reverse bias control circuit, 20 ... reverse bias application circuit, 2
1 ... Charging coil, 22 ... Biasing capacitor.

Claims (3)

[Claims] 1. A pulse gas laser oscillation method for continuously generating pulsed discharge between a pair of main electrodes to output pulsed laser light, the polarity of which is opposite to that of the preceding pulsed discharge during the pulsed discharge. A pulsed gas laser oscillation method characterized in that a voltage having a polarity is applied between the respective main electrodes. 2. The main capacitor is charged by the power supplied from the high-voltage power source, and the main capacitor is discharged to reduce its charge to 1
In a pulse gas laser oscillation device that supplies pulsed laser light by supplying pulsed discharge to a pair of main electrodes, a voltage having a polarity opposite to the voltage polarity applied from the main capacitor to each main electrode is applied to each main electrode. A reverse bias power source applied between, a first switch connected between the main capacitor and each of the main electrodes, a second switch connected between the reverse bias power source and each of the main electrodes, The first switch is closed and the second switch is opened during the pulse discharge, and the first switch is opened during the pulse discharge.
And a reverse bias control circuit for opening the switch and closing the second switch. 3. The main capacitor is charged by the power supplied from the high-voltage power supply, and the main capacitor is discharged to reduce its charge to 1
In a pulse gas laser oscillator that supplies a pair of main electrodes to generate a pulse discharge to output a pulse laser beam, the high-voltage power supply is supplied through the main capacitor to be charged, and the main capacitor slowly discharges. And a reverse bias applying circuit for applying a voltage having a polarity opposite to that of a voltage applied from the main capacitor to the respective main electrodes during the pulse discharge to each of the main electrodes. Pulse gas laser oscillator.