JPH0220083A - Discharge type excimer laser apparatus - Google Patents

Abstract

PURPOSE:To facilitate control, to make it possible to make an apparatus compact and to improve laser oscillating efficiency by applying spiker pulses for starting discharge to main discharge electrodes without using a transformer, and automatically operating a discharge continuing circuit after the discharge. CONSTITUTION:A third capacitor (main capacitor) 12 is charged with a power source 41 through a charging coil 15 to -VM [V] beforehand. Therefore, after electric charge has been transferred from a first capacitor 13, the sum of the voltage Vpeak generated across both ends of the second capacitor 14 and a charging voltage VM of the third capacitor, i.e., the voltage of Vpeak+VM [V] is applied across main discharge electrodes 2. Therefore, when Vpeak+VM [V] reaches the discharge breakdown voltage of laser gas, discharge is started between the main discharge electrodes 2. When the discharge is started, the impedance of the laser gas is rapidly decreased, and the electric charge that is charged in the third capacitor 12 to -VM [V] is discharged between the main discharge electrodes 2 through the second capacitor 14 and the preliminary ionization electrodes 30. Thus the discharge for laser oscillation is continued.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a discharge starting circuit (spiker circuit), a discharge 1,
This invention relates to a spiker/sustainer type discharge type excimer laser device having a 1F sustainer circuit (sustainer circuit).

[Prior Art] In recent years, excimer laser devices have been developed as light sources that can emit high-output ultraviolet rays. Among these, so-called spiker-sustainer discharge excimer lasers have high efficiency and reduce the load on electrical circuit elements. It has the characteristics of being lightweight and having a long device life.

Conventionally, this type of device has had a structure as shown in FIG. (Appl, I'hys, Lett, 47(2), 1
5 July 1985 Happ1. Phys, Lett
, 46 (4), 15 February 1985
7FJ2, inside the laser scum chamber 1 are main discharge electrodes 2. Preliminary ionization energy generation source 3,
Gas circulation fan 4. A gas cooler 5 is arranged, and an optical resonator 6 is interposed between the main TL electrodes 2 for amplifying discharge light generated between the main discharge electrodes 2 and causing laser oscillation.

In such a device, when a trigger signal is input to the trigger signal input terminal 7, a discharge start pulse (hereinafter referred to as spiker pulse) is output from the discharge start pulse generator 8 to the primary coil 10 of the transformer 9, and the transformer A conduction voltage is generated in the secondary coil 11 of 9, that is, a spiker pulse is induced. This spiker pulse is applied to the main discharge electrode 2 via the capacitor 20 and causes the pre-ionization energy generation source 3 to discharge the pre-ionized laser gas. The above is the operation of the spiker circuit.

On the other hand, the capacitor 20 stores electric charge in advance to maintain the discharge (however, the charging voltage is less than the laser gas discharge starting voltage), and the laser gas causes discharge between the main discharge electrodes 2, causing the laser gas to discharge. After the impedance of the main discharge electrode 2, the capacitor 20
A discharge sustaining current automatically flows through the closed circuit consisting of the secondary coil 11, and the discharge between the main discharge electrodes 2 is sustained, leading to laser oscillation. At this time, if the magnetic flux flowing through the core of the transformer 9 is saturated, the rise of the discharge sustaining current flowing from the capacitor 20 becomes faster, and a good discharge for laser oscillation can be achieved.

The above is the operation of the sustainer circuit.

[Problems to be Solved by the Invention] However, in the conventional device as described above, since a transformer is used to obtain the spiker pulse, the structure is not only complicated and it is difficult to miniaturize the device. Since the spiker pulse generation efficiency, that is, the energy transfer efficiency in the transformer is low, the oscillation efficiency of the laser device 7 is also low.

In addition, since the discharge starting circuit and the circuit for pre-ionizing the laser gas are separate, it is difficult to adjust the timing of the pre-ionization, and it is difficult to make a glow discharge between the main discharge electrodes that is effective for laser oscillation. It was 1 toshi.

This invention was made in view of these points, and it is possible to pre-ionize the laser gas always at the optimal timing, and to apply the spiker pulse between the main discharge electrodes without using a transformer, with high efficiency and good performance. The object of the present invention is to provide a discharge type excimer laser device in which main discharge is performed.

[Means for Solving the Problem] The present invention includes a charge transfer circuit that transfers the charge stored in a first capacitor to a second capacitor via a pre-ionization electrode, and a charge transfer circuit that transfers the charge stored in a first capacitor to a second capacitor, and A discharge starting circuit applies the sum of the charging voltages of the third capacitor to the main discharge electrode via the pre-ionization electrode, and the charge stored in the third capacitor is transferred to the second capacitor and the pre-ionization electrode. E if! ! The above object is achieved by including a discharge sustaining circuit that causes discharge between the main discharge electrodes via the electrodes.

[Function] In this invention, a charge f3 row circuit is added to the discharge starting circuit, and the charge of the first capacitor charged in advance is transferred to the second capacitor for starting discharge via the preliminary type 1liI electrode. Then, the sum voltage of the charging voltage of this second capacitor and a third capacitor for maintaining discharge, which is charged separately, is applied to the main discharge electrode as a spiker pulse. As described above, since the present invention does not use a transformer in the discharge starting circuit, it is possible to downsize the device, and since there is no energy loss in the transformer, the energy efficiency of laser oscillation can be increased.

In addition, a spark discharge occurs in the preliminary TLm'J electrode at the same time as the 8th line of charge, and the laser gas is preliminarily ionized by the generated ultraviolet rays. Preliminary type J51[ will be performed at the same time, so that the timing of preliminary ionization will not be delayed.

Then, in the present invention, when the discharge starts and the impedance of the laser gas rapidly decreases, the charge stored in the third capacitor is discharged between the main discharge electrodes via the second capacitor and the pre-ionization electrode, i.e. Since the discharge sustaining circuit operates automatically, control is easy.

[Example code] FIG. 1 is a circuit diagram showing an embodiment of the present invention.

A preliminary ionization electrode 30, a gas circulation fan 4, and a gas cooler 5 are arranged in the laser gas chamber 1, and an optical resonator 6 is provided between the main discharge electrodes 2 to amplify discharge light and cause laser oscillation. is interposed.

First, when a trigger is applied to the trigger signal input terminal 7 of a high-voltage, high-speed switch (hereinafter simply referred to as a switch) such as a thyratron, spark gap, rail gap, or thyristor, the switch 16 becomes conductive. Here, the first
The capacitor (storage capacitor) 13 is powered in advance by a power source 40 via a charging coil 15.
+VS [V], and when the switch 16 becomes conductive, the charge stored in the first capacitor 13 is transferred to the switch 16 - the spare type 11! The second capacitor 14 (peaking capacitor) passes through the If electrode 30
to move to. At this time, the preliminary ionization electrode 30 generates a spark discharge, and the generated ultraviolet rays preliminarily ionize the laser gas between the main discharge electrodes 20, making it easier for the spiker discharge to occur uniformly. In addition, since the current rises rapidly in the above operation, the charging coil 15 has a large inductance, and almost no current flows.

In addition, the third capacitor (main capacitor) 12
is previously charged to −vit[v] by the power source 41 via the charging coil 15.

Therefore, the voltage V p generated across the second capacitor 14 after the charge is transferred from the second capacitor 13
The sum of eak and the charging voltage VM of the third capacitor, ie, V peak + VM [V] (7) voltage will be applied between the main discharge TL pole 2. Therefore, V p
When eak+V M [V] reaches the discharge breakdown voltage of the laser gas, a discharge starts between the main discharge electrodes 2 . Note that the voltage V peak is larger than the voltage VM, and the capacity of the third capacitor 12 for maintaining discharge is considerably larger than the capacity of the second capacitor 14 for starting discharge. The above is the operation of spiker discharge.

Next, when discharge starts, the impedance of the laser gas rapidly decreases, and the electric charge of the third capacitor 12 charged to -VM [V] is transferred to the second capacitor 14, the reserve type 1! ! ! A discharge occurs between the main discharge electrodes 2 via the electrode 30, and the discharge for laser oscillation is maintained. Then, the discharge light is amplified by the optical resonator 6, resulting in laser oscillation. The above is the operation of the sustainer circuit.

[Effects of the Invention] As described above, according to the present invention, a spiker pulse for starting discharge is applied to the main discharge electrode without using a transformer,
After discharging, the discharge sustaining circuit is automatically operated, so
Control is easy, the device can be made smaller, and there is no energy loss in the transformer, so the laser oscillation efficiency can be improved. In addition, pre-ionization is automatically performed at a certain timing before a voltage higher than the discharge breakdown voltage of the laser gas is applied.
Stable discharge occurs without external timing adjustment.

Furthermore, in the discharge starting circuit, the sum of the voltages of the discharge starting capacitor and the discharge sustaining capacitor is applied to the main discharge electrode, so the power supply voltage can be lowered and the insulation structure can be made relatively simple. This also improves safety.

Such a discharge type excimer laser device is extremely useful as a light source for projection reduction exposure devices for manufacturing integrated circuits, precision processing devices using lasers, and the like.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional example. [Symbols of main parts Jj2] 1... Laser gas chamber 2... Main discharge electrode 3... Preliminary ionization energy generation source 6... Optical resonator 7... Trigger signal input terminal 8... Discharge starting pulse generator 9...Transformer 10...Transformer secondary side coil 11...Transformer secondary side coil 12...Third capacitor 13...First capacitor 14...No. 2 capacitor 16...switch 30...preliminary ionization electrode 4041...power supply

Claims (1)

[Scope of Claims] A discharge type excimer laser device having a discharge starting circuit and a discharge sustaining circuit, comprising: a charge transfer circuit that transfers charge stored in a first capacitor to a second capacitor via a pre-ionization electrode; a discharge starting circuit that applies a sum voltage of charging voltages of the second capacitor and a pre-charged third capacitor between the main discharge electrodes via a pre-ionization electrode; A discharge type excimer laser device comprising: a discharge sustaining circuit that causes discharge between the main discharge electrodes via the second capacitor and the pre-ionization electrode.