JPH0818134A - Laser oscillator - Google Patents

Abstract

PURPOSE:To always obtain a high level laser output without dependence on laser medium by obtaining a freely selected excitation density while keeping stabilized glow discharge. CONSTITUTION:In a laser oscillator comprising a pair of main electrodes 20a, 20c, a plurality of pairs of preliminary ionizing electrodes 22a, 22c and a discharge circuit for discharging these main electrodes 20a, 20c and preliminary ionizing electrodes 22a, 22c, at least one electrode of the main electrodes 20a, 20b is hollowed, a plurality of preliminary ionizing electrodes 22a, 22c are provided within this hollowed electrode, an aperture is formed in the discharge area of the main electrodes 20a, 20b having the hollowed portions and a movable shielding member 40 is provided for changing aperture width of the aperture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser oscillator having a pair of main electrodes and a plurality of pairs of UV (ultraviolet light) auxiliary electrodes.

[0002]

2. Description of the Related Art A discharge excitation laser device is widely used as a light source for material processing such as marking, punching and cutting of products. In particular, excimer lasers that generate strong laser light in the ultraviolet range utilize their characteristics to mark organic materials, ablation processing, fine processing of general materials, surface modification, light source for photochemical reaction, semiconductors. It is used as a light source for a reduction projection exposure apparatus used for optical lithography.

FIG. 18 shows a conventional UV preliminary electrode type lateral discharge excitation laser device (TEA laser device). In this laser device, a preliminary ionization electrode is provided in order to generate stable glow discharge. I am trying to provide it.

In FIG. 18, a laser tube 1 and a pressure wall 10 are shown.
In the space sealed by the pair of main electrodes 2a, 2
b, and several tens of pairs of preionization electrode groups 3a, 3b, 4 arranged in parallel on both sides of the main electrodes 2a, 2b in a direction perpendicular to the paper surface.
a, 4b, a blower 5 for circulating the laser medium gas, and a heat exchanger 6 are provided.

On the other hand, the discharge circuit 7 has a high-voltage power supply terminal 8 and
It has capacitors C1, C2, C3, a coil L1, and a high-speed switching element 9 such as a thyratron. This discharge circuit 7 causes a high repetition discharge between the main electrodes 2a, 2b to produce a pulse laser output. I am trying to get it.

The operation will be described. First, the capacitor C1 is charged to a predetermined voltage through the high voltage power supply terminal 8 and then the high speed switching element 9 is turned on to transfer electric charges to the secondary capacitors C2 and C3. It Then, during this charge transfer, the preionization electrode groups 3a, 3b, 4
A discharge is generated at a and 4b, and as a result of this preliminary discharge, initial electrons are generated between the main discharge electrodes. Then, after that, when the voltage of the secondary capacitors C2 and C3 reaches the discharge start voltage, a main discharge occurs between the main electrodes 2a and 2b, and as a result, the laser medium is excited and laser oscillation is performed.

By the way, in such a laser device,
The laser output can be improved by controlling the excitation density of the laser medium gas in the laser tube 1.

Therefore, in the conventional device, (1) the shape of the main electrode is changed to narrow the discharge width, (2) the discharge voltage is increased, (3) the capacities of the capacitors C1, C2 and C3 are increased. The method was used to increase the discharge density.
On the contrary, in order to reduce the discharge density, contrary to the above,
The discharge width of the main electrode is widened, the discharge voltage is lowered, and the capacities of the capacitors C1, C2 and C3 are reduced.

[0009]

However, when the shape of the main electrode is changed to narrow the discharge width, there is a drawback that the electrode is consumed greatly and the life of the electrode becomes very short. Also,
In order to change the shape of the main electrode to change the discharge width, it is necessary to disassemble the entire discharge circuit portion and replace the electrode, which takes time and labor.

Further, when the discharge voltage is increased, not only the load of the power source is increased, but also it is difficult to maintain stable glow discharge due to the increase of the discharge voltage, and arc discharge occurs. This will reduce the laser output and shorten the life of the electrode.

Further, if the capacitance of the capacitor is to be increased or decreased, the operating conditions will change unless the inductance of the discharge circuit 7 is adjusted.

On the other hand, when the electrode is changed to a flatter shape in order to widen the discharge width of the main electrode, there is a problem that the discharge is split into two left and right parts and the output light becomes a hollow beam. Further, in the method of lowering the discharge voltage, the laser output decreases, and it becomes difficult to maintain stable glow discharge and stable laser output, as in the case of increasing the discharge voltage.

The present invention has been made in view of such circumstances, and it is possible to obtain an arbitrary excitation density while maintaining a stable glow discharge, and always obtain a high laser output regardless of the type of laser medium. It is an object of the present invention to provide a laser oscillation device capable of

[0014]

According to the present invention, there is provided a laser oscillating device having a pair of main electrodes, a plurality of pairs of preliminary ionization electrodes, and a discharge circuit for discharging the main electrodes and the preliminary ionization electrodes. At least one of which is hollow, and the plurality of pairs of preionization electrodes are arranged in this hollow portion,
An opening is formed in the discharge area of the main electrode having a hollow portion, and a movable shield member for varying the opening width of the opening is provided.

[0015]

According to the present invention, the size of the discharge region is controlled by adjusting the width of the opening provided in the main electrode by the movable shield member, and thus an arbitrary excitation density can be easily obtained. it can.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, and the same reference numerals are given to the constituent elements that achieve the same functions as those of the conventional apparatus shown in FIG.

In FIG. 1, a pair of main electrodes 20a and 2a are provided in the space sealed by the laser tube 1 and the pressure wall 10.
0b, and several tens of pairs of preionization electrode groups 22a, 22b provided in the cavity 21 formed in one main electrode 20b,
22 c, a blower 5 that circulates a laser medium gas, a heat exchanger 6, and a rectifying plate 23 are provided.

The discharge circuit 7 has a high-voltage power supply terminal 8 and capacitors C1, C2, C as in the conventional structure shown in FIG.
3, a coil L1, and a high speed switching element 9 such as a thyratron.

In the above structure, the lower main electrode 20b has a cavity 21 inside, and 50% of the openings 24 having a diameter of about 2 to 3 mm are formed on the surface facing the other main electrode 20a.
The aperture ratio is about the same.

2 to 6 show various patterns of the opening 25 of the main electrode 20b.

In the case of FIG. 2, the slit openings 24 extending in the width direction of the main electrode are arranged in a row in the electrode longitudinal direction, and in the case of FIG. 3, the slits 24 extending in the longitudinal direction of the main electrode are aligned vertically and horizontally. In the case of FIG. 4, the slits 24 extending in the longitudinal direction of the main electrode are arranged vertically and horizontally, and in the case of FIG. 5, the circular or polygonal small hole openings 24 are aligned vertically and horizontally. In case of, a circular or polygonal small hole opening 24
It is arranged vertically and horizontally with a shift.

As described above, the cavity 21 is formed in the main electrode 20b having the opening 24 as described above, and several tens of pairs of preionization electrode groups 22a, 2 are formed in the cavity 21.
2b and 22c are provided. These pre-ionization electrode groups 22a, 22b, 22c correspond to one electrode group 22b, 2
2c is electrically coupled to the main electrode 20b, and the other electrode 2
2a is connected to ground. Note that one of the preionization electrode groups 22b and 22c may be omitted.

In the structure shown in FIG. 1 as described above, the laser tube 1 is filled with a laser medium gas consisting of, for example, several% of rare gas, 0.1 to 0.3% of halogen gas, and 90% of buffer gas, and the blower is blown. 5 circulates in the laser tube 1.
The gas flow velocity at this time is determined according to the repetition frequency of the laser.

In such a state, by turning on the switching element 9 of the discharge circuit 7, the charges charged in the capacitor C1 are pre-ionized electrode groups 22a, 22b, 22c.
To the secondary capacitors C2 and C3 via. At this time, the preionization electrode groups 22a, 22b, 22c are discharged,
Ultraviolet light is generated by the spark. The generated ultraviolet light irradiates the main discharge portion through the opening 24 formed in the main electrode 20b, thereby generating preionized electrons between the main electrodes.

After that, the secondary capacitors C2 and C3
Of the main electrodes 20a, 20
A main discharge is generated between points b, and as a result, the laser medium is excited and laser oscillation is performed.

Here, in the present apparatus, the main electrode 20b
The width L of the opening is set to an optimum width according to various lasers. Therefore, in this device, it becomes possible to easily obtain the optimum excitation density corresponding to various lasers between the main electrodes, and it is possible to generate a uniform glow discharge with a width corresponding to each opening width, Higher laser output than before can be obtained.

For example, in the case of a laser such as an ArF excimer laser or an F2 laser which requires a strong excitation density, if the aperture width L is narrowed as shown in FIG. Can be obtained (see FIG. 8).

Further, in the case of a XeCl excimer laser or the like which has a sufficient weak excitation density, the opening width may be widened as shown in FIG.

Next, another embodiment of the present invention will be described with reference to FIGS.

That is, in the embodiment in this case, FIG.
Alternatively, as shown in FIG. 11, the opening 25 of the main electrode 20b is formed.
The main electrode 20b is detachable from other parts of the main electrode 20b, thereby significantly reducing the time and labor for replacing the main electrode and facilitating the work for changing the opening width L of the main electrode 20b. There is. That is, the main electrode 20b is connected to the discharge circuit 7
Since it has been conventionally time-consuming and time-consuming to replace the electrodes because it is connected to the various components, the opening 25, which is the main target of electrode wear, is detachable from the main electrode 20b. This facilitates electrode replacement.

The connecting portion between the main electrode 20b and the opening 25 has a quick snap mechanism as shown in FIG. 13, for example. That is, FIG. 13 shows the details of the portion P of FIG. 12, in which the ball bearing 27 biased by the spring 26 is provided on the main electrode 20b side, and the recess 28 is formed on the opening electrode 25 side. Therefore, the opening electrode 25 can be attached to the main electrode 20b only by pushing the opening electrode 25 from above.

When the opening electrode 25 is attached or detached, the jig 30 is attached to the jig attachment hole 29 formed in the opening 25 as shown in FIGS. 12 and 14, and the jig 30 is attached. The opening electrode 25 is attached and detached by using this.

The main electrode 20b and the opening 25 may be connected by using a bolt 31 as shown in FIG.

FIG. 16 shows still another embodiment of the present invention. In this embodiment, it is slidable in the direction of arrow β in the space between the main electrode 20b and the preionization electrodes 22b, 22c. The pair of light shielding plates 40 are provided, and the opening electrode 25
The size of the discharge region is varied by adjusting the opening width of the, so that an arbitrary excitation density can be easily obtained.

FIG. 17 shows a specific example of the sliding mechanism of the light shielding plate 40, (a) is a plan view, (b) is a front view,
(c) is a side view.

In FIG. 17, the pair of shading plates 40 are slidable in the β direction along the guide members 41 provided at both ends thereof. The guide member 41 is fixed. Further, the four pins 42 attached to each light shielding plate 40 are fitted in the “C” -shaped guide groove 44 formed in the moving plate 43. An insulator rod 45 is attached to the moving plate 43, and the moving plate 43 is slid by moving the insulator rod 45 in the α direction. The insulator rod 45 is extended to the outside of the laser chamber via a flexible tube 46 provided on the pressure wall 10.

In this structure, when the light shielding plate 40 is slid in the β direction, the insulator rod 45 is slid in the α direction outside the laser chamber. As a result, the moving plate 43 moves in the α direction, and the pin 42 moves along the “H” -shaped guide groove 44 along with the movement. Then, the movement of the pin 42 causes the light blocking plate 40 to slide along the guide member 41 in the β direction.

As described above, in this embodiment, the aperture width of the aperture electrode 25 is adjusted by the light shielding plate 40 to change the size of the discharge region, whereby an arbitrary excitation density can be easily obtained.

The structure for sliding the light shielding plate 40 is not limited to that shown in the above embodiment, and any mechanism may be adopted.

Further, although the rectifying plate 23 is arranged in the configuration of FIG. 1, the shapes of the main electrodes 20a and 20b may themselves have a rectifying effect. Due to such a rectifying effect, the vicinity of the preionization electrodes 22a to 22c can be sufficiently exhausted, the deteriorated gas near the preionization electrodes can be eliminated, and sufficient preionization characteristics can be obtained even at the time of high repeated discharge. it can.

[0042]

As described above, according to the present invention,
Pre-ionization is performed in the cavity provided in the main electrode, and the width of the region irradiated by the pre-ionization light is varied by the shielding member provided between the opening of the main electrode and the pre-ionization electrode, so that stable It is possible to easily obtain an arbitrary excitation density while maintaining the glow discharge, and it is possible to effectively deal with a laser medium that requires strong excitation density and a laser medium that is effective for weak excitation. A high laser output can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an example of an opening shape of an opening electrode.

FIG. 3 is a diagram showing an example of an opening shape of an opening electrode.

FIG. 4 is a diagram showing an example of an opening shape of an opening electrode.

FIG. 5 is a diagram showing an example of an opening shape of an opening electrode.

FIG. 6 is a diagram showing an example of an opening shape of an opening electrode.

FIG. 7 is a diagram showing a case where the opening width of the main electrode is narrowed.

FIG. 8 is a diagram showing the relationship between discharge width and laser output.

FIG. 9 is a diagram showing a case where the discharge width of the main electrode is widened.

FIG. 10 is a view showing a case where the opening of the main electrode is made detachable.

FIG. 11 is a view showing a case where the opening of the main electrode is made detachable.

FIG. 12 is a diagram showing a configuration of an attachment / detachment portion of an opening portion of a main electrode.

FIG. 13 is an enlarged view of the attachment / detachment mechanism.

FIG. 14 is a view showing a jig used for the attachment / detachment.

FIG. 15 is a diagram showing a configuration of an attachment / detachment portion of an opening portion of a main electrode.

FIG. 16 is a diagram showing an example in which a shielding plate is provided.

FIG. 17 is a view showing a moving mechanism of the shielding plate.

FIG. 18 is a view showing a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser tube 2 ... Main electrode 3,4 ... Preliminary ionization electrode 5 ... Blower 6 ... Heat exchanger 7 ... Discharge circuit 8 ... High-voltage power supply terminal 9 ... High-speed switching element 10 ... Pressure wall 20 ... Main electrode 21 ... Cavity 22 ... Pre-ionization electrode 23 ... Rectifier plate 24 ... Opening 25 ... Opening electrode 26 ... Spring 27 ... Ball bearing 28 ... Recessed portion 29 ... Jig mounting hole 30 ... Jig 31 ... Bolt 40 ... Shading plate 41 ... Guide member 42 ... Pin 43 … Moveable plate 44… Guide groove 45… Insulator rod 46… Flexible tube

Claims (1)

[Claims] 1. A laser oscillation device comprising a pair of main electrodes, a plurality of pairs of preionization electrodes, and a discharge circuit for discharging the main electrodes and the preionization electrodes, wherein at least one of the main electrodes is made hollow. The plurality of pairs of preionization electrodes are arranged in the hollow portion, an opening is formed in the discharge area of the main electrode having the hollow portion, and a movable shield member for varying the opening width of the opening portion is provided. A laser oscillating device characterized by the above.