JP3090796B2 - Excimer laser oscillation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excimer laser oscillating device, and more particularly to an excimer laser oscillating device capable of easily performing a high repetition operation.

[0002]

2. Description of the Related Art Excimer laser oscillation devices are expected to produce high repetition pulse oscillations with an average output of 1 kW as a high-output high-efficiency laser, and have been applied to a wide range of fields in the electronics and chemical industries such as semiconductor manufacturing. .

A discharge tube 1 of a conventional excimer laser oscillation device
Is shown in FIG. The laser gas s, which is the operating medium of the excimer laser, forms a flow path of the laser gas s in order to remove the metal vapor generated by the discharge and the laser gas s heated and partially ionized by the discharge from the discharge part. The inside is blown by a blower 2 which is a circulation means.

On the other hand, a strong arc discharge is instantaneously performed at the preliminary ionization electrodes 3a and 3b to generate ultraviolet light. The generated ultraviolet light preliminarily ionizes the laser gas s between the main discharge electrodes 4a and 4b. Here, the main discharge electrodes 4a, 4a
A pulse voltage is applied between b and glow discharge is performed, and the discharge excites molecules in the laser gas s to perform stimulated emission, thereby generating laser light. This laser light is extracted in a direction perpendicular to the paper surface. The pulse oscillation is repeatedly performed by repeating the discharge (pulse discharge) by the pulse voltage.

[0005]

FIG. 5 shows the flow rate distribution of the laser gas in each section inside the discharge tube 1 in the above-described conventional excimer laser oscillation device. In section A, section B, and section C, the flow path area is reduced, so that the flow velocity distribution is uniform, and the gas layer (hereinafter, referred to as a boundary layer) near the wall surface 6a of the discharge tube is made of gas having a low flow velocity.

However, the cross section D,
In the section E, the boundary layer 7 develops near the wall surface 6b. Immediately after discharge, the main discharge electrodes 4a, 4a
Since the boundary layer 7 contains the metal vapor evaporated from b, the electric resistance of the boundary layer 7 is low. Immediately after the discharge, the laser gas in the vicinity of the discharge part is also ionized, and the electric resistance is low. FIG. 6 shows the gas distribution of these gas layers 8 having a low electric resistance immediately after the discharge. Since the gas layer 8 having a low electric resistance connects between the main discharge electrodes, if a discharge is performed in this state, a current flows through the gas layer 8 having the low electric resistance, and laser light cannot be obtained.

After a lapse of time after the discharge, the metal vapor in the gas layer 8 having a low electric resistance diffuses into the mainstream portion due to turbulent mixing from the boundary layer, and the ionized laser gas also circulates. The electrical resistance recovers by going.

Therefore, after the discharge is performed, the next discharge cannot be performed until the electric resistance of the gas layer 8 having the low electric resistance is sufficiently high. Since the recovery of the electric resistance is proportional to the flow rate of the laser gas s in the discharge tube 1, if the flow rate of the laser gas s in the discharge tube 1 is sufficiently fast with respect to the pulse repetition period of the main discharge (experimentally 10 times or more). Such a problem does not occur.

However, since energy proportional to the cube of the flow rate of the laser gas s in the discharge tube 1 is required for the circulation of the laser gas, the discharge tube flow rate is actually limited, and the pulse repetition period of the main discharge is also limited. I have.

For the above-mentioned reasons, the conventional excimer laser oscillation device has a limitation in high repetition operation, and when applied to the field of semiconductor manufacturing and the like, the production speed is limited.

The present invention has been made in view of the above-described circumstances, and has as its object to provide an excimer laser oscillation device which enables a high repetition operation by providing a groove on a flow path wall surface in a discharge tube. .

[0012]

According to a first aspect of the present invention, there is provided an excimer laser oscillator according to the present invention, comprising: a discharge tube; a laser gas supplied into the discharge tube; Circulating means for circulating the laser gas in the discharge tube, a pre-ionization electrode for pre-ionizing the laser gas provided in the flow path of the laser gas in the discharge tube, and a pre-ionization electrode provided in the flow path of the laser gas in the discharge tube An excimer laser oscillation device having a pair of main discharge electrodes for exciting the pre-ionized laser gas, performing a pulse discharge between the main discharge electrodes, exciting the laser gas, and oscillating a pulse. A groove is provided in the wall of the flow path, and a part of the laser gas becomes a vortex due to the groove, and flows backward from the main flow at the bottom of the groove. Those that are configured to flow in the same direction as substantially the mainstream in the portion along the flow path wall surface of the groove.

[0013] It is effective that the groove is provided at least on the opposite wall surface of the circulated gas flow downstream of the main discharge electrode.

[0014]

According to the present invention, a groove is provided in the wall of the opposed flow passage in the discharge tube, and a part of the laser gas circulated by the groove becomes a vortex, and flows backward from the main flow at the bottom of the groove. By being configured to flow in substantially the same direction as the main flow in a portion along the flow path wall of the groove,
The metal vapor or ionized gas having a low electric resistance after discharge is separated from the main discharge electrodes without being connected between the main discharge electrodes by the eddy current. The electrical resistance is restored, and a discharge capable of laser oscillation can be performed.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The same parts as those of the conventional example shown in FIG. 4 are denoted by the same reference numerals, and the detailed description is omitted.

FIG. 1 shows a sectional view of a discharge tube 1 in a first embodiment of an excimer laser oscillation device according to the present invention. A flow path for flowing a laser gas s as a laser medium is formed in the discharge tube 1 by a blower 2 as a circulating means, and the laser gas is caused to flow into this flow path so that arc discharge is performed at the preliminary ionization electrodes 3a and 3b. Has become. Ultraviolet light is generated by the arc discharge, and the generated ultraviolet light preliminarily ionizes the laser gas s between the main discharge electrodes 4a and 4b. At this time, if glow discharge is performed between the main discharge electrodes 4a and 4b,
Molecules in a laser gas s, which is a laser medium, are excited to perform stimulated emission, and laser light is generated.

On the other hand, a groove 5 is provided in the flow tube wall of the circulated laser gas s in the discharge tube 1 on the downstream side of the main discharge electrodes 4a and 4b.

The groove 5 has a function of immediately discharging ionized gas or metal vapor immediately after discharge.

Next, the operation will be described.

The provision of the groove 5 allows
A part of the flow of the laser gas s near the groove 5 in the flow of the laser gas s is swirled as shown in FIG. That is, a part of the vortexed laser gas s flows backward at the bottom portion of the groove 5, but at a portion where the flow channel wall surface has been conventionally, that is, at a portion along the flow channel wall surface in the groove 5. It is almost the same direction as the main stream and has the same flow velocity. Here, as described above, laser light is generated by arc discharge at the preliminary ionization electrodes 3a and 3b and glow discharge between the main discharge electrodes 4a and 4b.

At this time, the gas layer 8 having a low electric resistance, which is composed of the vaporized metal vapor and the ionized gas existing immediately after the discharge, has a vortex as described above in the flow of the laser gas s. The electrodes are disconnected from the main discharge electrode without connecting the electrodes, and are discharged in a form as shown in FIG.

Therefore, by providing the groove 5, the electrical resistance between the main discharge electrodes is recovered in a short time after the discharge, and a discharge capable of laser oscillation can be performed.
High repetition operation becomes possible.

FIG. 3 is a sectional view of a discharge tube 1 in a second embodiment of the excimer laser oscillation device according to the present invention. In the second embodiment, the grooves 5a and 5b are provided on the flow path wall on both sides of the main discharge electrodes 4a and 4b. Since the other configuration is the same as that of the first embodiment, the same reference numerals are given and the description is omitted.

As described in the first embodiment, the groove 5b generates a vortex that connects the main discharge electrodes 4a and 4b immediately after the discharge and has a function of discharging the evaporated metal vapor and the ionized gas. Similarly, a vortex is also generated in the groove 5a. Kinetic energy is stored in these vortices.

On the other hand, at the moment when the discharge is performed, the laser gas s is instantaneously expanded because the laser gas s expands.
Some of them stop. The stopped laser gas s is strongly affected by the viscosity of the gas, and flows out from the center to the vicinity of the flow path wall surface. At this time, since the kinetic energy is stored in the vortex, the stopped laser gas s can flow in a short time after the stop. The effect is particularly strong in the vicinity of the flow channel wall surface, and can prevent the development of the boundary layer near the flow channel wall surface as described above.

Therefore, the electrical resistance between the discharge electrodes recovers within a short period of time after the discharge, and a discharge capable of laser oscillation can be performed, thereby enabling a high repetition operation.

[0027]

As described above, according to the excimer laser device of the present invention, a groove is provided on the wall surface opposite to the discharge tube, and a part of the laser gas flow as a medium of the excimer laser device is formed by the groove. Since it is configured to be a vortex and to flow backward from the main flow at the bottom of the groove and to flow in substantially the same direction as the main flow at a portion along the flow path wall of the groove, electric current flows between the main discharge electrodes. It is possible to prevent a gas having a low resistance from being combined, to recover the electric resistance between the main discharge electrodes in a short time after the discharge, and to perform a discharge capable of laser oscillation. As a result, the repetition period can be shortened as compared with the conventional high repetition operation of the excimer laser device, and the production speed can be increased as compared with the conventional one when applied to fields such as semiconductor manufacturing.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the inside of a discharge tube in a first embodiment of an excimer laser oscillation device according to the present invention.

FIG. 2 is a sectional view showing the inside of a discharge tube in the first embodiment of the excimer laser oscillation device according to the present invention.

FIG. 3 is a sectional view showing the inside of a discharge tube in a second embodiment of the excimer laser oscillation device according to the present invention.

FIG. 4 is a cross-sectional view showing the inside of a discharge tube in a conventional example of an excimer laser oscillation device according to the present invention.

FIG. 5 is a sectional view showing the inside of a discharge tube in a conventional example of an excimer laser oscillation device according to the present invention.

FIG. 6 is a cross-sectional view showing the inside of a discharge tube in a conventional example of an excimer laser oscillation device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge tube 2 Blower (circulation means) 3a Pre-ionization electrode 3b Pre-ionization electrode 4a Main discharge electrode 4b Main discharge electrode 5, 5a, 5b Groove 6a, 6b Discharge tube internal channel wall surface 7 Boundary layer 8 Gas layer with low electric resistance s laser gas

Claims (2)

(57) [Claims] 1. A discharge tube, a laser gas supplied into the discharge tube, circulating means for circulating the laser gas into the discharge tube, and a laser gas installed in a flow path of the laser gas in the discharge tube. A preionization electrode to be ionized, and a pair of main discharge electrodes that are provided in the flow path of the laser gas in the discharge tube and excite the preionized laser gas, perform a pulse discharge between the main discharge electrodes. In the excimer laser oscillation device that excites and excites the laser gas and performs pulse oscillation, a groove is provided on the opposed flow path wall surface in the discharge tube, and a part of the laser gas becomes a vortex due to the groove, and the main flow at the bottom of the groove becomes Characterized in that it is configured to flow backward and to flow in substantially the same direction as the main flow at a portion of the groove along the flow path wall surface. Shimareza oscillating device. 2. The above-mentioned groove is formed on a flow path wall of a circulated laser gas on the downstream side facing the main discharge electrode.
The excimer laser oscillation device according to claim 1, wherein at least one is provided.