JPH01162390A - Excimer laser device - Google Patents

Abstract

PURPOSE:To enable a spiker transformer to be dispensed with by a method wherein the charging charges are transferred from a pre-ionizing condenser to a peaking condenser, and a primary discharge is made to occur through the charges stored in an exciting primary condenser as a pre-ionization is kept occurring. CONSTITUTION:When the charges stored in a pre-ionizing condenser 24 are transferred to a peaking condenser 27 through a pre-ionizing spark electrode 26, the laser gas is pre-ionized by ultraviolet rays generated from the pre- ionizing spark electrode 26, whereby the state that a primary discharge is likely to occur uniformly is gradually developed. The charged voltage of an excitation primary condenser 21 is applied to primary discharge electrodes 2A and 2B through the intermediary of the peaking condenser 27 and the pre-ionizing spark electrode 26. Thus, when the laser gas is pre-ionized to reach such a state that the primary discharge is able to start, the discharge starts automatically between the primary discharge electrodes 2A and 2B. Then, the primary discharge of the gas laser is maintained mainly through the charges stored in the excitation primary condenser 21.

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]

The present invention provides a discharge type excimer laser device in which a main discharge is generated by the charge in the excitation main capacitor while pre-ionizing the main capacitor by transferring the charge from the pre-ionization capacitor to the peaking capacitor. Therefore, main discharge can be generated stably and automatically without using a spy power transformer.

[Conventional technology]

Conventionally, as this type of discharge type excimer laser device, one shown in FIG. 3 has been proposed.

In FIG. 3, 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. C17 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, which are made of spark electrodes, X-ray sources, etc., are disposed facing each other so as to sandwich the main discharge electrodes 2A and 2B.
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 laser light 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 11B of the spiker 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 spiker transformer 11, and when a pulsed trigger signal S1 is applied to its trigger signal input terminal 13A, the primary winding of the spiker transformer 11 By flowing a trigger pulse current into the secondary winding 11A, a spark electrode V 7 R is generated in the secondary winding 11B, thus starting a main discharge between the main discharge electrodes 2A and 2B.

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. 3, in a state where no main discharge occurs between the main discharge electrodes 2A and 2B, the main excitation capacitor 12 is charged to a charging voltage vM of, for example, several (kV) by the main excitation power source 14. There is. FIG. 4 is an example of a signal waveform diagram showing signals of each part of the apparatus shown in FIG. 3, and is a schematic diagram.

In this state, a trigger signal Sl (FIG. 4(A)) is applied 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 spark electrode VTR is generated at B, and this is superimposed on the charging voltage VM of the main excitation capacitor 12 (FIG. 4 (B)), so that the voltage applied between the main discharge electrodes 2A and 2B increases the discharge of the laser gas. By exceeding the starting voltage,
Main discharge starts.

At this time, the charged charge of the main excitation capacitor 12 becomes a discharge current of 1 spC (Fig. 4(C)).
- Secondary winding 11B of spiker transformer 11 = main discharge electrodes 2A, 2B - Laser light LA (Fig. 4 (D)) is emitted from optical resonator 3 by flowing through the circuit of main capacitor 12 for excitation. Ru.

Eventually, when the charging voltage A (FIG. 4(B)) of the main excitation capacitor 12 finishes discharging, the discharge current TSP stops flowing (FIG. 4(C)), and the optical resonator 3 is activated by the laser beam LA. (Fig. 4(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. 4(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 spy power transformer 11 as a spy power 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 of a capacitor 12, a secondary winding 11A 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. 3, a spiker transformer 11 is used to obtain the spy force voltage (A) for starting the discharge of the laser gas.First, the configuration of the excimer laser device as a whole is complicated. It is inevitable that it will be large, and the spy power transformer 1
Since the energy transfer efficiency in No. 1 was low, the oscillation efficiency of the excimer laser device as a whole was still insufficient.

In addition, in the conventional configuration shown in FIG. 3, the drive 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 spiker circuit. Although it is designed to be provided separately from the main discharge electrodes 2A and 2B, it is actually a synchronous operation that generates the spy force 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 is a simple method that can always stably shift the laser gas in an optical resonator from a pre-ionization state to a discharge state without requiring a conventional spike transformer. This paper attempts to propose an excimer laser device with the following configuration.

[Means for solving problems]

In order to solve this problem, in the present invention, the charge in the preionization capacitor 24 is transferred to the peaking capacitor 27 through the preionization spark electrode 26, and the laser gas is preionized by the preionization spark electrode 26. By applying the charging voltage of the main excitation capacitor 21 to the main discharge electrodes 2A and 2B via the peaking capacitor 27 and the pre-ionization spark electrode 26, a main discharge is caused in the laser gas.

[Effect]

When the charge in the pre-ionization capacitor 24 starts to be transferred to the peaking capacitor 27 through the pre-ionization spark electrode 26, the laser gas is pre-ionized by the ultraviolet rays generated from the pre-ionization spark electrode 26, thereby causing a main discharge. A state that tends to occur uniformly can be gradually formed.

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 to use the spiker transformer 11 as in the conventional case.

〔Example〕

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

[1] In FIG. 1, in which parts corresponding to those in FIG. 3 of the first embodiment are denoted by the same reference numerals, the positive electrode of the main excitation capacitor 21 is connected to the main discharge electrode 2B, and the negative electrode is connected to the main discharge electrode 2B. is grounded through the saturable reactor 22. An excitation main power source 23 is connected to the positive electrode of the excitation main capacitor 21,
Main power supply for excitation 23 - main capacitor for excitation 21 - saturable reactor 22 - earth - circuit LPI of main power supply for excitation 23
As a result, the voltage v8 across the main excitation capacitor 21 is charged to about +20 (kV), for example.

The negative electrode of the preionization capacitor 24 is connected to the end of the saturable reactor 22 on the excitation main capacitor 21 side, and the positive electrode is connected to one end of the preionization spark electrode 26 and the main excitation capacitor 21 through a switch 25 made of, for example, a thyratron. Connected to the discharge electrode.

The other end of the pre-ionization spark electrode 26 is connected to the negative electrode of the pre-ionization capacitor 24 via the peaking capacitor 27, and thus the trigger signal Sll is applied to the trigger signal input terminal 25A of the switch 25. When IO- is turned on, the charge in the pre-ionization capacitor 24 is transferred to the peaking capacitor 27 through the switch 25 and the pre-ionization spark electrode 26, and at this time, the pre-ionization spark electrode 26 is discharged. By irradiating the laser gas with the ultraviolet rays generated by the laser gas, the laser gas is pre-ionized into a glow discharge state.

A pre-ionization power supply 28 is connected to the positive electrode of the pre-ionization capacitor 24, and a pre-ionization power supply 28 is connected to the pre-ionization capacitor 24-saturable reactor 22-earth-pre-ionization power supply 28 circuit LP2. The voltage 5 across the ionization capacitor 24 is charged to about 5 kV or higher, for example.

In the above configuration, when no main discharge occurs between the gas laser main body GLAO main discharge electrodes 2A and 2B, and no discharge occurs at the preliminary ionization spark electrode 26,
Excitation main capacitor 21 and pre-ionization capacitor 24
is charged via the above-mentioned charging circuits LP1 and LP2.

In this state, when the switch 25 is turned on by applying the trigger signal Sll to its trigger signal input terminal 25A, the charge in the pre-ionization capacitor 24 is transferred from the pre-ionization capacitor 24 to the switch 25 to the secondary ionization spark electrode 26. It is transferred to the peaking capacitor 27 by flowing through the pre-ionization loop LP3 of the peaking capacitor 27 and the secondary ionization capacitor 24.

At this time, the pre-ionization spark electrode 26 discharges, thereby pre-ionizing the laser gas between the main discharge electrodes 2A and 2B and starting glow discharge.

At the same time, the voltage across the excitation main capacitor 21 is
is applied between the main discharge electrodes 2A and 2B through the peaking capacitor 27 and the pre-ionization spark electrode 26.

In fact, as the charging of the peaking capacitor 27 progresses, the voltage 2 across it increases, and as a result, the excitation main capacitor 2 is connected between the main discharge electrodes 2A and 2B.
A state is obtained in which a difference voltage between the charging voltage (1) 8 of the peaking capacitor 27 and the charging voltage (2) of the peaking capacitor 27 is applied.

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 in the main excitation capacitor 21 is discharged through the main excitation capacitor 21 - main discharge electrodes 2B, 2A - secondary ionization spark electrode 26 - peaking capacitor 27 - discharge circuit LP4 of the main excitation capacitor 21. do.

In fact, when the main discharge starts, the charge in the pre-ionization capacitor 24 is also discharged through the two main discharge electrodes and 2B.

At the same time, as the leakage current to the saturable reactor 22 gradually increases, the reactance of the saturable reactor 22 rapidly decreases, causing the excitation main capacitor 22 to
1 of charge mainly flows through the main discharge circuit LP5 of the main capacitor for excitation 21-main discharge electrode 2B, 2A-saturable reactor 22-main capacitor for excitation 21.

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

Eventually, when the charge in the main excitation capacitor 21 finishes discharging, 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. At this time, as the current flowing through the saturable reactor 22 becomes smaller, the saturable reactor 22 transitions to a non-saturated state and returns to a state where its reactance is large, and thus the main discharge circuit LP5 is equivalently cut off in the saturable reactor 22. Become.

Thus, one discharge cycle is completed, and the excimer laser device EXMA as a whole returns to the charging operation state of the main excitation capacitor 21 and the pre-ionization capacitor 24.

According to the configuration shown in FIG. 1, before starting main discharge between the GLAO main discharge electrodes 2A and 2B of the gas laser main body, the charge in the pre-ionization capacitor 24 is transferred to the peaking capacitor 27 via the pre-ionization spark electrode 26. When the pre-ionization state becomes optimal for causing a main discharge, the charged charge of the main excitation capacitor 21 is automatically transferred to the main discharge electrode 2A.
By causing the main discharge between 2B and 2B, the laser gas can automatically and stably shift from the pre-ionization state to the main discharge state.

In this way, by eliminating the need to provide the spiker transformer 11 (Fig. 3) as in the conventional case, the overall configuration of the excimer laser device EXMA can be further simplified and miniaturized, and at the same time, the laser Light generation efficiency can be increased.

[2] Second Embodiment FIG. 2, in which parts corresponding to those in FIG. 1 are given the same reference numerals, shows another embodiment of the present invention. 21 is charged with a polarity opposite to that shown in FIG.

In the configuration of FIG. 2, the pre-ionization spark electrode 26 is connected to the pre-ionization capacitor 24 in the same manner as in FIG.
When the charged charge moves to the peaking capacitor 27, a preliminary ionization operation is performed.

At this time, the voltage applied between the main discharge electrodes 2A and 2B is as follows: Since the charging voltage 9 of the main excitation capacitor 21 has the opposite polarity to that shown in FIG. The value is the sum of the voltage ■9 and the charging voltage VP of the peaking capacitor 27. Therefore, the discharge voltage applied to the partial discharge electrodes 2A and 2B is controlled by the main excitation capacitor 21 and the peaking capacitor 27.
A main discharge can be generated between the main discharge electrodes 2A and 2B by effectively utilizing the charged charges.

Thus, compared to the case shown in FIG. 1, the charging voltage 4 of the main excitation capacitor 21, and therefore the output voltage of the main excitation power supply 23, can be reduced by this amount.

〔Effect of the invention〕

As described above, according to the present invention, when transferring the charge charged in the preionization capacitor to the peaking capacitor, the laser gas can be preionized by the preionization spark electrode, and the charging voltage of the main excitation capacitor can be peaked. By applying the voltage between the main discharge electrodes via the pre-ionization capacitor and the pre-ionization spark electrode, a series of operations for pre-ionizing the laser gas and then transitioning to the main discharge can be executed stably and automatically. Therefore, since there is no need to use a spiker transformer as in the conventional case, the overall configuration of the excimer laser device can be made smaller and simpler, and the laser generation efficiency can be improved.

[Brief explanation of the drawing]

Fig. 1 is a line connection diagram showing one embodiment of the excimer laser device according to the present invention, Fig. 2 is a line connection diagram showing another embodiment of the invention, and Fig. 3 is a line connection diagram showing a conventional excimer laser device. The route connection diagram, FIG. 4, is a signal waveform diagram showing the signals of each part. 1... Laser gas chamber, 2A, 2B...
...Main discharge electrode, 3...Optical resonator, 11...
...Subaika transformer, 21... Main capacitor for excitation, 22... =17- Saturable reactor, 24... Capacitor for pre-ionization, 25... ... Switch, 26 ... Spark electrode for preliminary ionization, 27 ... Peaking capacitor, EXMA ... Excimer laser device, GLA ... Gas laser main body.

Claims (2)

[Claims] (1) While transferring the charged charge of the pre-ionization capacitor to the peaking capacitor through the pre-ionization spark electrode, the laser gas is pre-ionized by the pre-ionization spark electrode, and the charging voltage of the excitation main capacitor is changed to the peaking capacitor. An excimer laser device characterized in that a main discharge is generated by applying a voltage to a main discharge electrode via a pre-ionization spark capacitor and the pre-ionization spark electrode. (2) The excimer laser device according to claim 1, wherein the pre-ionization capacitor and the excitation main capacitor are charged via a saturable reactor.