JPH03288487A - Discharge excitation excimer laser device - Google Patents

Abstract

PURPOSE:To provide a discharge excitation excimer laser device having a variable capacity automatic preionization circuit of good electrical insulation properties by connecting a peaking capacitor and an excitation discharge electrode in parallel, by connecting one connecting point to a high voltage side and by grounding the other connecting point through a gap of a preionized electrode. CONSTITUTION:A plurality of preionized electrodes 6 are arranged in a longitudinal direction of an excitation discharge electrode 5, and an inductor 7 is connected to each pair thereof. Since the inductor 7 prevents current concentration on a specific preionized electrode 6, it is possible to realize preionization of extremely good uniformity and to improve uniformity of excitation discharge. Since electric potential of the preionized electrode 6 is at ground electric potential, dielectric breakdown is not caused by creeping discharge, etc., between the preionized electrode 6 and a peripheral ground electric potential part.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a discharge excited excimer laser device.

BACKGROUND OF THE INVENTION A rare gas halogen excimer laser is a high-output gas laser that oscillates in the ultraviolet region, and is used in a wide range of applications such as a light source for ultrafine processing in semiconductor lithography and chemical processes. Excitation methods for rare gas halogen excimer laser devices include electron beam excitation and discharge excitation, and the latter is widely used because it has a relatively simple configuration and is capable of high repetition oscillation.

A conventional discharge excited excimer laser device will be explained below.

FIG. 2 is a sectional view of the discharge excited excimer laser device.

A mixture of rare gas and halogen 7 gas is sealed in the pressure vessel 8 at a pressure higher than atmospheric pressure, and a negative discharge occurs between the excited discharge electrodes 5.5 provided inside the pressure vessel 8. The laser gas in the main discharge region is excited by this. Note that 6 is a preliminary ionization electrode, and 9 is a high voltage source terminal.

Since the rare gas halogen excimer laser device is a laser device that requires extremely high excitation density, it is necessary to pre-ionize the discharge area before starting the excited discharge to make the excited discharge steep. Become.

BACKGROUND ART Conventionally, as a pre-ionization method for industrial excimer laser devices, a capacity transfer automatic pre-ionization method with a simple device configuration has been used. FIG. 3 is a block diagram of a conventional capacity transfer automatic pre-ionization circuit. While the switch 1 is open, the charging capacitor 2 is charged via the charging coil 3. When the switch 1 is closed, the electric charge of the charging capacitor 2 is transferred to the peaking capacitor 4. At this time, the pre-ionization electrode 6 provided in the capacitance transfer circuit consisting of the switch 1, the charging capacitor 2, and the peaking capacitor 4 is transferred to the peaking capacitor 4. Spark discharge occurs at the gap. By irradiating the excited discharge space with ultraviolet light generated from this discharge, the laser gas in the excited discharge space is ionized. When the voltage between the terminals of the peaking capacitor 4 reaches the discharge start voltage of the excitation discharge electrode 5, an excitation discharge occurs. This completes one laser operation, but generally a thyratron or the like is used for the switch 1, and the laser operation is repeated.

The voltage applied to the peaking capacitor 4 is 20-odd kV.
extremely high. With the circuit configuration shown in FIG. 3, since this ultra-high voltage is applied to the pre-ionization electrode 6, dielectric breakdown is likely to occur inside the pressure vessel 8. In addition, 7 is a preliminary ionization electrode 6
is an inductor connected in series with.

Problems to be Solved by the Invention However, in the conventional configuration described above, the degree of freedom in design is limited, such as the need to use a large amount of insulating material that reduces the generation of impurity gas around the discharge part in order to ensure thorough insulation measures. There was an issue of

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a discharge-excited excimer laser device equipped with a capacitance transfer automatic pre-ionization type port having excellent electrical insulation properties.

Means for Solving the Problems To achieve this object, the discharge-excited excimer laser device of the present invention employs a capacity transfer automatic pre-ionization type discharge that irradiates an excited discharge area with ultraviolet light generated by a discharge between pre-ionization electrodes. In an excitation excimer laser device, a peaking capacitor and an excitation discharge electrode are connected in parallel, one connection point is connected to the high voltage side, and the other connection point is grounded through a gap between preionization electrodes.

Effect: With this configuration, the part to which a high voltage is applied in the pressure vessel is only one of the excited discharge electrodes, realizing a discharge excited excimer laser device equipped with a capacitance transfer automatic pre-ionization type circuit with excellent electrical insulation properties. I can do it.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a discharge-excited excimer laser device in one embodiment of the present invention. A preliminary ionization electrode 6 is provided between a connection point on the ground potential side between the excitation discharge electrode 5 and the peaking capacitor 4 and a ground potential point of the charging coil 3.

Note that 1, 2, 7, and 8 are a switch, a charging capacitor, and an inductor pressure vessel, respectively, as in FIG.

Generally, the excitation discharge in an excimer laser device is a uniform discharge over the entire length of the elongated excitation discharge electrode 5. In order to achieve such a uniform excited discharge over a wide area, it is necessary to uniformly pre-ionize the entire discharge region. Therefore, a plurality of pre-ionizing electrodes 6 are arranged in the longitudinal direction of the excited discharge electrode 5, and - An inductor 7 was connected in series to each set. Since the inductor 7 prevents current concentration on a specific pre-ionization electrode 6, the pre-ionization becomes extremely uniform and the uniformity of the excited discharge also increases. According to experiments, it was confirmed that the overall efficiency of the laser (the ratio of the charging energy to the charging capacitor and the laser pulse energy) was improved by about 50%. Improving the overall efficiency leads to a reduction in the load on circuit components such as electrodes and switch elements, and suppression of gas deterioration, thereby extending the life of the entire laser device. Note that the operation of the circuit is exactly the same as in the case of the circuit configuration of the circuit shown in FIG. Dielectric breakdown due to creeping discharge between the ground potential part and the ground potential part does not occur. Since high voltage is applied to only one of the excitation discharge electrodes, the amount of insulating material used can be significantly reduced. Insulating materials such as tetrafluoroethylene resin are a source of impurity gases, and reducing their usage leads to suppressing gas pollution and extending the life of the gas. Furthermore, as insulation design has become easier and the degree of freedom in design has increased, it has become a challenge to reduce the size and weight by about 30% compared to conventional products.

Effects of the Invention As described above, the present invention has a capacitance transfer automatic pre-ionization type circuit with excellent electrical insulation because the potential of the pre-ionization electrode is set to earth potential, and has advantages such as realizing uniform pre-ionization and suppressing gas contamination. The present invention aims to realize a high efficiency, high output oscillation excimer laser device having the following characteristics.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a discharge-excited excimer laser device according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of the discharge-pumped excimer laser device, and Fig. 3 is a block diagram of a conventional capacitance transfer automatic pre-ionization circuit. be. 2...Charging capacitor, 4...Peaking capacitor, 5...Excitation discharge electrode, 6...
...Preliminary ionization electrode.

Claims (1)

[Claims] Prior to the excitation discharge to excite the laser medium, the charge stored in the charging capacitor is excited by ultraviolet light generated by the discharge between the pre-ionization electrodes installed in the path of the transfer current when transferring it to the peaking capacitor. In a discharge-excited excimer laser device of the capacity transfer automatic pre-ionization type that irradiates the discharge area, the peaking capacitor and the excited discharge electrode are connected in parallel, one connection point is connected to the high voltage side, and the other connection point is connected in parallel. A discharge-excited excimer laser device grounded through the gap of the pre-ionization electrode.