JPH01162389A - Excimer laser device - Google Patents

Abstract

PURPOSE:To enable a primary discharge to take place automatically and stably without using a spiker transformer by a method wherein charging charges are transferred from a pre-ionizing charge generating circuit provided with first and second pre-ionizing condensers to a peaking condenser. CONSTITUTION:The charge of a first and second pre-ionizing condensers 24A and 24B of a pre-ionizing charge generating circuit 29 is made to start transferring to a peaking condenser 27 through a pre-ionizing spark electrode 26. Then, the laser gas between electrodes 2A and 2B is pre-ionized by ultraviolet rays generated from a pre-ionizing spark electrode 26, consequently the state that a primary discharge is apt to occur uniformly can be gradually developed. Therefore, a spiker transformer can be dispensed with.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an excimer laser device, and is particularly suitable for application to a discharge type excimer laser device.

[Summary of the invention]

In a discharge type excimer laser device, the present invention provides for excitation while preionizing by transferring charge from a preionization charge generation circuit having first and second preionization capacitors to a peaking capacitor. By causing the main discharge to occur due to the charge in the main capacitor, the main discharge can be generated stably and automatically without using a spiker transformer.

[Conventional technology]

As a conventional discharge type excimer laser device of this type, one shown in FIG. 2 has been proposed.

In FIG. 2, EXMA indicates the excimer laser device as a whole, and has a gas laser main body GLA. The gas laser main body GLA has a laser gas chamber 1 in which a laser gas consisting of a halogen gas (e.g. Cj2 gas), a rare gas (e.g. Xe gas), and a buffer gas (e.g. He gas) is sealed, and a pair of main discharge electrodes 2A and A laser beam LA is emitted in a direction perpendicular to the plane of the paper from an optical resonator 3 constituted by a facing mirror disposed between 2B and facing each other in a direction perpendicular to the plane of the paper.

Further, a pair of pre-ionization generating elements 4A and 4B made of, for example, a spark electrode, an X-ray source, etc., are arranged opposite to each other so as to sandwich the two main discharge electrodes and 2B, and this pre-ionization generating element 4A
By pre-ionizing the laser gas between the electrodes 2A and 4B into a glow discharge state, a main discharge is uniformly generated between the main discharge electrodes 2A and 2B, and thus the laser beam LA is efficiently generated.

One main discharge electrode 2A is connected to, for example, the positive electrode of a relatively large capacity excitation main capacitor 12 via the secondary winding '41A11B of the spy power transformer 11, and the other main discharge electrode 2B is connected to the excitation main capacitor 12. It is connected to the negative electrode of the capacitor 12, and their common connection point is grounded.

A discharge starting pulse generator 13 is connected to the primary winding 11A of the spy transformer 11, and when a pulsed trigger signal S1 is applied to its trigger signal input terminal 13A, the primary winding of the spy transformer 11 By flowing a trigger pulse current into the secondary winding 11A, a spy voltage VTR is generated in the secondary winding 11B, and the main discharge electrodes 2A and 2B are
The main discharge is started during this period.

Note that 5 is a gas cooler, and 6 is a gas circulation fan for generating as much discharge as possible.

In the configuration shown in FIG. 2, when no main discharge occurs between the main discharge electrodes 2A and 2B, the main excitation capacitor 12 is charged at a charging voltage of, for example, several (kV) by the main excitation power source 14. is being charged. FIG. 3 is an example of a signal waveform diagram showing signals of each part of the device shown in FIG. 2, and is a schematic diagram.

In this state, a trigger signal SL (Fig. 3 (A)) is sent to the trigger signal input terminal 13A of the discharge starting pulse generator 13.
is given, the secondary winding 11 of the spiker transformer 11
A spy force voltage VTR is generated at B, and this is superimposed on the charging voltage H of the main excitation capacitor 12 (Fig. 3 (B)), so that the voltage applied between the main discharge electrodes 2A and 2B increases from the laser gas By exceeding the discharge starting voltage of
Main discharge starts.

At this time, the charging charge of the main excitation capacitor 12 is discharged by the main capacitor 12 as the discharge current 1sp<FIG. 3(C)).
Laser light LA (FIG. 3 (D)) is emitted from the optical resonator 3 by flowing through the circuit of - the secondary winding 11B of the spy power transformer 11 - the main discharge electrodes 2A, 2B - the main excitation capacitor 12. Ru.

Eventually, when the charging voltage ■ and (Fig. 3 (B)) of the main excitation capacitor 12 finish discharging, the discharge current ISI' stops flowing (Fig. 3 (C)), and the optical resonator 3 emits the laser beam. The radiation of LA is stopped (Fig. 3 (D)).

In this operation, the trigger signal S1 is input to the trigger signal input terminal 13.
is repeated each time given to A, thus optical resonator 3
The laser beam LA (FIG. 3(D)) is intermittently emitted for a relatively short period of time, for example, several tens of nanoseconds (ns).

This conventional discharge type excimer laser device has a discharge starting pulse generator 13 and a spiker transformer 11 as a spy force circuit for starting laser gas discharge, and an excitation main circuit for maintaining the started laser gas discharge. As a so-called spiker/sustainer type discharge excimer laser device having a circuit including a capacitor 12, a secondary winding 11B of the spiker transformer 11, the main discharge electrodes 2A and 2B, and the excitation main capacitor 12, it has relatively high efficiency and Since the load on the circuit elements is light, there is an advantage that the life of the device as a whole is long.

[Problem that the invention seeks to solve]

However, according to the conventional configuration shown in FIG. 2, since the spiker transformer 11 is used to obtain the spy force voltage VTR for starting the discharge of the laser gas, the structure of the excimer laser device as a whole becomes complicated and large. However, since the energy transfer efficiency in the spiker transformer 11 is low, the oscillation efficiency of the excimer laser device as a whole is still insufficient.

In addition, in the conventional configuration shown in FIG. 2, the driving means for the pre-ionization generating elements 4A and 4B that generate glow discharge between the main discharge electrodes 2A and 2B is replaced by a discharge starting pulse generator constituting a spy force circuit. Although it is designed to be provided separately from the main discharge electrode 2A and 2B, it is actually a synchronous operation that generates the spiker voltage VTR in accordance with the timing when the laser gas between the main discharge electrodes 2A and 2B is pre-ionized to a sufficient degree for practical use. It has been difficult to realize a control circuit that allows stable execution at all times.

The present invention has been made in consideration of the above points, and provides an excimer laser with a simple configuration that can always stably shift laser gas from a pre-ionization state to a discharge state without requiring a conventional spy power transformer. This is an attempt to propose a device.

[Means for solving problems]

In order to solve this problem, in the present invention, the charged charges generated in the pre-ionization charge generation circuit 29 having the first and second pre-ionization capacitors 24A and 24B are used for peaking through the pre-ionization spark electrode 26. The laser gas between the electrodes 2A and 2B is pre-ionized by the spark electrode 26 for pre-ionization while being transferred to the capacitor 27, and the charging voltage of the main capacitor 21 for excitation is changed via the capacitor 27 for peaking and the spark electrode 26 for pre-ionization. A main discharge is caused in the laser gas by applying the voltage to the main discharge electrodes 2A and 2B.
One ends of the pre-ionization capacitors 24A and 24B are connected in common to the pre-ionization power source 28 to be charged by the pre-ionization power source, and a switch 25 is connected in parallel to the second pre-ionization capacitor 24B. By turning on the switch 25 and reversing the polarity of the charging voltage of the second pre-ionization capacitor 24B, the first and second pre-ionization capacitors 24A
and peaking capacitor 27 from the series circuit of 24B.
to generate a charging charge that is transferred to

[Effect]

When the charges in the first and second pre-ionization capacitors 24A and 24B of the pre-ionization charge generation circuit 29 start to be transferred to the peaking capacitor 27 through the pre-ionization spark electrode 26, the charges are generated from the pre-ionization spark electrode 26. By pre-ionizing the laser gas between the electrodes 2A and 2B by the ultraviolet rays, it is possible to gradually create a state in which the main discharge tends to occur uniformly.

The charging voltage of the main excitation capacitor 21 is applied to the main discharge electrodes 2A and 2B via the peaking capacitor 27 and the pre-ionization spark electrode 26, and the laser gas is thus prepared to a state where it can start main discharge. When ionized, a discharge is automatically started between the main discharge electrodes 2A and 2B, and thereafter the main discharge of the laser gas is maintained mainly by the charge in the main excitation capacitor 21.

In this way, the laser gas can be stably and automatically transferred from the pre-ionized state to the main discharge state, thereby eliminating the need for the spy power transformer 11 as in the prior art.

In addition to this, particularly in the present invention, the charging voltage of the second preionization capacitor 24B is reversed when moving the charged charge, so that the first and second preionization capacitors 24A and A sufficiently high charging voltage can be generated using a capacitor having a relatively low breakdown voltage as 24B.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, in which parts corresponding to those in FIG. 2 are given the same reference numerals, the negative electrode of the main excitation capacitor 21 is
B, and the positive electrode is connected to the charging coil 22.
It is grounded through.

The main power source for excitation 23 is connected to the negative electrode of the main capacitor for excitation 21, and the main power source for excitation 23 - the main capacitor for excitation 21 - the charging coil 22 - the ground - the main power source for excitation 23
The voltage across the excitation main capacitor 21 is charged to, for example, about -20 [kV] by the circuit LPI.

The negative electrode of the first pre-ionization capacitor 24A is connected to the excitation main capacitor 21 side end of the charging coil 22, and the second pre-ionization capacitor 24B is connected to the ground side end of the charging coil 22. The negative electrode of is connected.

First and second pre-ionization capacitors 24A and 24B
The positive electrodes are connected to each other and connected to a pre-ionization power source 28.
connected to. Furthermore, a second pre-ionization capacitor 24
A switch 25 made of, for example, a thyratron is connected in parallel to B, and thus a pre-ionization charge generation circuit 29 is formed by the first and second pre-ionization capacitors 24'A and 24B, the pre-ionization power supply 28, and the switch 25. has been done.

The first pre-ionization capacitor 24A is connected to the pre-ionization power supply 28 - the first pre-ionization capacitor 24A - the charging coil 22 - the ground - the charging circuit LP2 of the pre-ionization power supply 28.
For example, the voltage at both ends of A is 2.5 CkV)
It will be charged until it reaches a certain level.

Further, the second pre-ionization capacitor 24B has a voltage VSZ across it of 2.5 (kV) between the pre-ionization power supply 28 - the second pre-ionization capacitor 24B - earth - the charging circuit LP2B of the pre-ionization power supply 28. ).

The negative end of the second pre-ionization capacitor 24B is connected to the positive electrode of the peaking capacitor 27 through the pre-ionization spark electrode 26, and at the same time the main discharge electrode 2A.
The negative electrode of the peaking capacitor 27 is connected to the negative electrode of the first preionization capacitor 24A.

Thus, when the trigger signal Sll is applied to the trigger signal input terminal 25A of the switch 25 and the switch 25 is turned on, the electric charge of the second pre-ionization capacitor 24B is transiently transferred to the switch 2.
5, the polarity of the voltage VS2 across the pre-ionization capacitor 24B is reversed. As a result, the first and second preionization capacitors 24A and 24B
A charged charge having a voltage equal to the sum of the voltage V g H and 3□ moves to the peaking capacitor 27 through the pre-ionization spark electrode 26 .

At this time, the laser gas is irradiated with ultraviolet rays generated by the discharge of the pre-ionization spark electrode 26, thereby pre-ionizing the laser gas into a glow discharge state.

In the above configuration, when no main discharge occurs between the GLAO main discharge electrodes 2A and 2B of the gas laser main body, and no discharge occurs at the preliminary ionization spark electrode 26, the excitation main capacitor 21 and the first And second pre-ionization capacitors 24A and 24B are charged via the above-mentioned charging circuits LPI, LP2A and LP2B.

At this time, the voltages VSI and Vs□ across the first and second pre-ionization capacitors 24A and 24B are equivalently equivalent to the pre-ionization spark electrode 26 and the peaking capacitor 2.
Since the 7 series circuits have mutually opposite polarities and substantially equal absolute value voltages, there is no movement of the charged charge to the peaking capacitor 27 via the pre-ionization spark electrode 26.

In this state, when the switch 25 is turned on by applying the trigger signal Sll to its trigger signal input terminal 25A, the polarity of the voltage VSZ across the second pre-ionization capacitor 24B is reversed, so that the pre-ionization spark electrode First and second pre-ionization capacitors 24A and 24 are connected to both ends of 26 and peaking capacitor 27.
A voltage equal to the sum of voltages v, 1 and v3□ across B is applied.

As a result, the charges in the first and second pre-ionization capacitors 24A and 24B start moving to the peaking capacitor 27 through the pre-ionization spark electrode 26.

At this time, by discharging the spark electrode 26 for pre-ionization, the laser gas between the main discharge electrodes 2A and 2B is pre-ionized to start glow discharge, but at the same time, the charging voltage ■N of the main capacitor 21 for excitation peaks. The voltage is applied between the main discharge electrodes 2A and 2B via the pre-ionization capacitor 27 and the pre-ionization spark electrode 26.

Here, since the charging voltage ① of the excitation main capacitor 21 and the charging voltage VP of the peaking capacitor 27 have the same polarity, the charging voltage V
A voltage equal to the sum of M and V is applied, and as the peaking capacitor 27 is actually charged, the voltage V2 across it increases, so the voltage applied between the main discharge electrodes 2A and 2B also gradually increases. Go.

As the glow discharge gradually expands, the impedance of the laser gas between the main discharge electrodes 2A and 2B rapidly decreases, so that a main discharge starts between the main discharge electrodes 2A and 2B.

At this time, the charge of the main excitation capacitor 21 is transferred through the main discharge circuit LP5, which is composed of the main excitation capacitor 21 - the peaking capacitor 27 - the pre-ionization spark electrode 26 - the two main discharge electrodes, and 2B - the main excitation capacitor 21. Discharge.

In fact, when the main discharge starts, the charges in the first and second pre-ionization capacitors 24A and 24B are also discharged through the main discharge electrodes 2A and 2B.

Therefore, the state in which the laser gas between the main discharge electrodes 2A and 2B generates laser light is maintained.

When the charge in the main excitation capacitor 21 is eventually discharged, the discharge current flowing through the main discharge circuit LP5 becomes smaller, so that no discharge occurs between the main discharge electrodes 2A and 2B, and as a result, no laser light is generated. .

One discharge cycle is completed, and the excimer laser device EXMA as a whole includes the main excitation capacitor 21 and the first and second preionization capacitors 24A and 24.
Return to the state of charging B.

According to the configuration shown in FIG. 1, before starting the main discharge between the GLAO main discharge electrodes 2A and 2B of the gas laser main body, the charges in the first and second pre-ionization capacitors 24A and 24B are transferred to the pre-ionization spark electrode. 26 to the peaking capacitor 27, and when the pre-ionization state becomes optimal for generating a main discharge, the excitation main capacitor 2 is automatically
1 charge is main discharged between the main discharge electrodes 2A and 2B. In this way, the laser gas can automatically and stably transition from the pre-ionization state to the main discharge state.

In this way, it is not necessary to provide the spiker transformer 11 (FIG. 2) as in the conventional case, which makes it possible to further simplify and downsize the entire structure of the excimer laser device EXMA. , the generation efficiency of laser light can be increased.

In addition, according to the configuration shown in FIG. 1, the first and second pre-ionization capacitors 24A and 24B are equivalently connected in parallel during charging as the pre-ionization charge generation circuit 29. During pre-ionization, by inverting the voltage across the second pre-ionization capacitor 24B, the charging voltage V 3 H+ V 3 is almost doubled.
□ can be supplied to the pre-ionization spark electrode 26, thereby making it possible to use capacitors with low withstand voltage as the first and second pre-ionization capacitors 24A and 24B, and to reduce the output voltage of the pre-ionization power source 28. By further reducing the pre-ionization generation circuit 29, the pre-ionization generation circuit 29 can be further simplified and miniaturized.

In the above-mentioned embodiment, the charging voltages of the first and second pre-ionization capacitors 24A and 24B, I and V
Although the case has been described in which S2 is configured to have approximately the same value, the configuration is not limited to this, and the configuration may be such that charging voltages that are different from each other are generated.

〔Effect of the invention〕

As described above, according to the present invention, when the charged charge of the pre-ionization capacitor is transferred to the peaking capacitor, the pre-ionization spark electrode can pre-ionize the optical resonator, and the charging voltage of the main excitation capacitor can be By applying it between the main discharge electrodes via the peaking capacitor and the pre-ionization spark electrode,
A series of operations in which the laser gas is pre-ionized and then transferred to the main discharge can be executed stably and automatically. Therefore, since there is no need to use a spy force transformer as in the conventional case, the structure of the excimer laser device as a whole can be made smaller and simpler, and the laser generation efficiency can be improved.

In addition, according to the present invention, two pre-ionization capacitors are prepared which are equivalently connected in parallel to each other during charging as a charge generation circuit for pre-ionization, and the voltage across one of the capacitors for pre-ionization is controlled during discharging. By inverting the charge generation circuit, the configuration of the pre-ionization charge generation circuit can be further simplified and miniaturized.

[Brief explanation of the drawing]

Fig. 1 is a line connection diagram showing an embodiment of an excimer laser device according to the present invention, Fig. 2 is a line connection diagram showing a conventional excimer laser device, and Fig. 3 is a signal waveform diagram showing signals of each part thereof. It is. 1... Laser gas chamber, 2A, 2B...
...Main discharge electrode, 3...Optical resonator, 11...
... Spy power transformer, 21 ... Main capacitor for excitation, 22 ... Charging coil, 24A,
24B...First and second capacitors for pre-ionization, 25...Switch, 26...Spark electrode for pre-ionization, 27...Capacitor for peaking , EXMA...Excimer laser device, G
LA...Gas laser main body.

Claims (2)

[Claims] (1) While transferring the charge generated in the pre-ionization charge generating circuit having the first and second pre-ionization capacitors to the peaking capacitor through the pre-ionization spark electrode, the pre-ionization spark electrode The main discharge is caused by pre-ionizing the laser gas and applying the charging voltage of the excitation main capacitor to the main discharge electrode via the peaking capacitor and the pre-ionization spark electrode, The charge generation circuit connects one end of the first and second pre-ionization capacitors to the pre-ionization power supply, and is charged by the pre-ionization power supply, and also charges the second pre-ionization capacitor. It has a configuration in which a switch is connected in parallel to the capacitor for pre-ionization, and by turning on the switch to reverse the polarity of the charging voltage of the second capacitor for pre-ionization, the first and second pre-ionization capacitors are connected in parallel. An excimer laser device characterized in that a charged charge is generated to be transferred from a series circuit of capacitors to the peaking capacitor. (2) A patent in which the first pre-ionization capacitor and the excitation main capacitor are charged through a charging coil connected between the other ends of the first and second pre-ionization capacitors. An excimer laser device according to claim 1.