JPH0787254B2 - High pressure gas laser device and processing method using the laser - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high pressure gas laser device and a processing method using the laser, and particularly to a high pressure gas laser device suitable for a large diameter and high output excimer laser, And a processing method using the laser.

[Conventional technology]

As a technology for increasing the diameter of a conventional discharge-excited excimer laser, see RL 1988 Proceedings No. 64
Corona UV as described on page (CLEO'88, p.64)
A method using preionization is known. This is because after applying a voltage between the main electrodes, a corona discharge is generated in one of the main electrodes with a certain time delay, and the UV light contained in this causes preionization of the main discharge space and trigger action. The main discharge is started by.

[Problems to be Solved by the Invention]

The above-mentioned prior art uses UV light accompanying corona discharge for preionization, and it is theoretically easy to increase the diameter of the discharge in the electrode width direction of the main discharge space, but the discharge in the electrode gap direction There is a limit to the uniformity of the laser beam, and there is a problem that a laser beam with a large diameter cannot be generated.

The present invention has been made in view of the above points, and an object thereof is to realize a large discharge diameter not only in the electrode width direction but also in the electrode gear cup direction, and as a result, a large diameter laser beam. It is to provide a high pressure gas laser device for generating.

[Means for Solving the Problems]

In order to achieve the above object, in the present invention, the high-voltage side electrode and the low-voltage side electrode of the main discharge electrode are alternated so as to be parallel to the laser optical axis and form at least two sets of discharge parts in layers. Or a pre-ionization means for pre-ionizing the discharge space prior to the main discharge between the main discharge electrodes, and a multi-folded laser beam having a time delay with respect to the voltage application to the main discharge electrodes. It was done.

[Action]

Since the high-voltage side electrode and the low-voltage side electrode are arranged alternately in parallel to the laser optical axis and form two or more sets of discharge parts in layers, the main discharge electrodes are arranged in layers. If a large diameter uniform discharge is formed in the electrode width direction at the discharge part,
A large-diameter laser beam can be obtained as a whole.
Further, since the preionization source is a laser beam, the beam cross section can be arbitrarily shaped, and a large volume discharge space can be preionized uniformly by making multiple turns using a reflecting mirror. As a result, a large-volume uniform discharge can be obtained, and a laser beam having a large diameter can be generated.

〔Example〕

Hereinafter, a high pressure gas laser device of the present invention will be described in detail based on embodiments of the drawings.

An embodiment of the present invention is shown in FIG. 1 and FIG. In the figure, the main laser device 1 is, for example, a XeCl excimer laser, and the main discharge part 2 thereof has high-voltage side main electrodes 3a, 3b, 3c.
Layered small discharge part 2 formed by alternately arranging the low-voltage side main electrodes 4a and 4b in parallel with the laser optical axis.
It consists of a, 2b, 2c and 2d. Peaking capacitors C _2a , C _2b ,
C _2c and C _2d are the corresponding main discharge electrode pairs 3a-4a, 3b-4a, 3b-
4b, 3c-4c, respectively. High voltage side main electrode 3
The a, 3b and 3c are connected to the charging capacitor C ₁ and the charging inductance L via the inductances L ₁ , L ₂ and L ₃ . Furthermore, the charging capacitor C ₁ is a high voltage switch SW,
It is connected to a high-voltage charging power source (not shown). The main discharge part 2 is arranged in the gas container 5, and the total reflection mirror 6 and the output mirror 7 constitute a part of the gas container 5. Outside the main laser device 1, a small laser device 8 as a preliminary ionization source,
For example, a UV laser such as a KrF excimer laser is installed, and laser light 9 emitted from the laser passes through a beam shaping optical system 10 including a cylindrical lens and the like, and each of the layered main discharge portions is formed by folding reflecting mirrors 11 and 12. It is designed to pass through.

The reflection mirror 12 is a total reflection mirror 6, which is coated so as not to reflect the laser wavelength of the main laser device.
The output mirror 7 corresponds to the wavelength of the laser beam 9 for preionization,
It is coated to be non-reflective.

A delay device 14 is provided between the preionization laser 9 and the trigger device 13 of the main laser device 1 to provide a time difference between the command signals of the two.

First, the inductance L ₀
The charging capacitor C ₁ is charged with a predetermined high voltage V _s via the. The command signal of the trigger device 13, a high voltage switch SW is closed, charges stored in the C ₁ is, C ₁ → SW → C _2a
→ L ₁ loop, C ₁ → SW → C _2b → L ₂ loop, C ₁ → SW → C _2c
It moves to the peaking capacitors C _2a , C _2b , C _2c , and C _2d via the resonance circuit of the loop of L _{2 and} the loop of C ₁ → SW → C _2d → L ₃ . The values of the inductances L ₁ , L ₂ and L ₃ are the pulse charging time T _o to the peaking capacitors C _2a , C _2b , C _2c and C _2d .
Are adjusted to be sufficiently longer than the discharge time of the main discharge, for example, 5 μs to 50 μs.
For example, as shown in FIG. 3, the delay device 14 causes a time T _d (T _d
It is set so that the laser light of the laser device 8 for preionization is emitted with a delay of T ₀ ).

In the time region up to t <T _d , no preionization occurs in the main discharge space, so the discharge start voltage V _B1 of the impulse (about 5 μs to 50 μs) between the layered main electrodes is the corresponding DC Sufficiently higher than discharge start voltage V _B0 (V _B1 10
× V _B0 ) has been confirmed experimentally.

The pulse charging voltage V _p of the peaking capacitor is set so that V _B0 << V _p <V _B1 (1), the pre-ionization laser beam 9 is incident with a delay time of T _d , and the folding mirrors 11 and 12 are used. When turned back one after another, the multi-layer main discharge space is preionized one after another. Main laser device 1
Assuming that the resonator length is 1 m and the pulse of the laser beam for pre-ionization is two round trips in the optical axis direction of the main laser device, the traveling distance is 4 m. It has been experimentally confirmed that the attenuation rate due to the propagation of the laser light in the gas is several% / m or less, and there is almost no attenuation even when the vehicle travels the above traveling distance, and the preionization effect is maintained. For reference, comparing this with other preionization sources, it becomes as shown in FIG. A ₁ ,
A ₂ is the normal position of the main electrode, and A ₁ and A ₃ are the positions of the main electrode when the gear gap between the main electrodes is doubled. Assuming that the preionization source is behind the main electrode A ₁ , the preionization electron density n _e
Have the same value at the intermediate position of A ₁ A ₂ (n _e 10 ⁶ c
m ^-3 ). Since the light source of corona UV and spark UV is basically a point light source or a parallel arrangement of them, as the distance from the light source increases, the preionization electron density decreases extremely, and discharge in the penetration distance direction occurs. It can be seen that it is difficult to make uniform. After the preionization laser beam is incident, a discharge is started between the main electrodes with a time delay of about τ50ns, but since electrons of n _e 10 ⁶ cm ^-3 already exist as seed electrons due to preionization, the entire main discharge space is covered. A uniform discharge is obtained over the entire length.

According to the present embodiment, a laser beam having a small propagation attenuation is used as the preionization source, and this is used by multiply folding, so that a large volume of space can be preionized uniformly, and a high-pressure high-pressure gas laser device can be obtained. Is effective. In addition, in this embodiment, the main electrode space is formed as a set of multi-layer small gap discharge spaces, and the applied voltage V _s for a single small main discharge is formed.
Can be realized at a comparatively low voltage according to the gear, and therefore, the measures for insulating the laser device can be facilitated and the charging power source can be made compact.

5 and 6 show a second embodiment of the present invention. In this embodiment, the main discharge electrode consists of a pair of electrodes 3,4. Then, the laser beam 9 for pre-ionization is reflected by the folding mirrors 11 and 12.
By this, a large number of diffractions are returned by this, and thereby the main discharge space is uniformly preionized.

The present embodiment has an effect that a high-pressure gas laser device having a large diameter can be provided with a simple structure.

7 and 8 show a third embodiment of the present invention. In this embodiment, the folding mirrors 11 and 12 are arranged on both side surfaces of the main laser device 1 so that the preliminary ionizing laser light 9 intersects the optical axis of the main laser device 1. According to this embodiment, there is an effect that a large-volume discharge space can be uniformly preionized, and a high-pressure high-pressure gas laser device can be provided. Further, since the optical axis of the main laser device 1 and the optical axis of the laser beam 9 for preliminary ionization intersect, the folding mirrors 11 and 12 and the total reflection mirror 6,
The reflective film of the output mirror 7 has an effect that it is sufficient to consider only a single wavelength.

FIG. 9 shows a fourth embodiment of the present invention. In the embodiment shown in the figure, the main discharge electrodes 4a, 3a, 4b, 3b, 4c are all porous aperture electrodes having a large number of small holes. A corona electrode 15 surrounded by a dielectric material such as ceramics is arranged on the back side of the uppermost main electrode, and is connected to a high voltage portion via a delay device 14. After a pulse voltage is applied to the high-voltage side main discharge electrodes 3a, 3b, a high-voltage pulse is applied to the corona electrode 15, and by its preionization action and trigger action,
First, only the main discharge space 2a in the uppermost layer starts main discharge, and laser oscillation starts. Since each main electrode is provided with a large number of small holes, the leakage light of UV light passing through these openings serves as a preliminary ionization source and a trigger source for the main discharge space 2b in the next stage, Main discharge begins. In this manner, layered main discharges are successively generated, and a laser beam having a large diameter is generated as a whole.

According to the present embodiment, it is easy to increase the discharge in the electrode width direction, and it is also possible to increase the diameter of the discharge in the direction of the electrode gear by providing a multi-layer discharge, and to provide a high-pressure high-pressure gas laser device. The effect is that you can do it.

FIG. 10 shows a fifth embodiment of the present invention. In the embodiment shown in the figure, the main discharge electrodes 4a, 3a, 4b, 3b, 4c are all mesh-shaped electrodes. Then, on the back side of the main electrode 4a of the uppermost layer, minute gears 16a, 16b, ... Are provided, and one end of each gearup electrode has ballast inductances 17a, 17b ,.
And the other end of each gear electrode is connected to the ground potential via the inductances 17a'17b ',. High-voltage side main discharge electrodes 3a, 3
After the pulse voltage is applied to b, a high voltage pulse voltage is applied to the gear electrode, and the main discharge space 2a of the uppermost layer starts the main discharge by the preionization action and the trigger action of the spark UV light. Laser oscillation starts. Since each main electrode is a mesh-shaped electrode, leakage light passing through the openings serves as a preliminary ionization source and a trigger source for the main discharge space 2b in the next stage, and the main discharge in the next stage starts. In this manner, layered main discharges are successively generated, and a laser beam having a large diameter is generated as a whole. In the present embodiment, in order to obtain uniform discharge in the electrode width direction, a large number of preionization gap electrodes are arranged in parallel not only in the axial direction but also in the width direction.

According to this embodiment, there is an effect that a high-pressure high-pressure gas laser device can be provided.

FIG. 11 shows a sixth embodiment of the present invention. In the embodiment shown in the figure, the peaking capacitors C _2a , C _2b , and C _2c are all integrally molded ceramic capacitors. If the main component of the ceramic is, for example, SrTiO ₃ , it is possible to easily manufacture a ceramic having a relative dielectric constant of about εs 1500.
If this ceramic is regarded as a pulse shaping circuit element, if the distance in the propagation direction of the pulse voltage is l, then the pulse width T _p is Given in. Where C is the speed of light. Conventionally, water (εs80) has been used as a large-capacity pulse shaping circuit capacitor, but according to the present embodiment, by using the integrally formed ceramic capacitor, it is possible to perform pulse shaping with a small size and a long pulse width. There is an effect.

FIG. 12 is an application example of the present invention. The large-diameter laser beam generated by the large-diameter high-pressure gas laser device 1 of each of the above-described embodiments, for example, XeCl excimer laser, is irradiated to large-area polycrystalline Si 18a, 18b, 18c, ... It is intended to If you do this,
Since a large-diameter laser beam is used, it is possible to anneal a sample with a single irradiation, and it is possible to remove an annealing defect that has occurred in a conventional beam overlapping portion.

Further, the duration of one pulse of the high pressure gas laser beam is extremely short, usually about 30 ns in the case of XeCl excimer laser, and the plurality of irradiated materials 18a, 18b, 18c, ... Are continuously moved without stopping. Even in this case, it is possible to perform high-precision continuous machining without causing positional displacement, and it is possible to provide a high-speed machining system.

FIG. 13 is another application example of the present invention. As shown in the figure,
In the case of a system in which a plurality of laser devices 1a, 1b, 1c are operated in parallel, one laser 8 provided outside is operated as a preionization source and a trigger source. According to this application example, there is an effect that a plurality of large-capacity large-diameter laser systems can be operated.

In each of the embodiments of the present invention described above, the pressure difference between the inside and outside of the apparatus with the total reflection mirror 6 and the output mirror 7 as boundaries can be eliminated by further setting the enclosed gas pressure to about atmospheric pressure.
There is an effect that the mechanical stress of the total reflection mirror 6 and the output mirror 7 can be relaxed.

Further, in each of the above-described embodiments of the present invention, the thickness t ₀ of the multilayer main electrode is set to 1/10 or less of the thickness of the main discharge gear d (single layer) so that the boundary portion of the laser beam due to the main discharge of each layer. Is not self-sustaining, and there is an effect that a laser beam having a large diameter can be equivalently obtained.

Further, in each of the above embodiments of the present invention, the rise of the pulse voltage applied to the main electrode, in combination with being sufficiently slow, by using a solid state element for the high voltage switch element,
There is an effect that the life of the laser device can be extended.

〔The invention's effect〕

According to the present invention described above, since the high-voltage side electrodes and the low-voltage side electrodes are alternately arranged to obtain a large-volume main discharge part equivalently, it is possible to provide a high-pressure high-pressure gas laser device. it can. Further, since the multi-folded laser light is used as the preionization source, it is possible to uniformly preionize a large-volume discharge space, so that a high-pressure high-pressure gas laser device can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view of an electrode portion showing an embodiment of a high pressure gas laser device of the present invention, FIG. 2 is a longitudinal sectional view of FIG. 1, and FIG. 3 is a voltage between main electrodes and time in an embodiment of the present invention. FIG. 4 is a characteristic diagram showing the relationship between the distance and electron density in the preionization source, FIG. 5 is a perspective view of the electrode portion showing the second embodiment of the present invention, and FIG. FIG. 7 is a vertical sectional view of FIG. 5, FIG. 7 is a perspective view of an electrode portion showing a third embodiment,
8 is a vertical sectional view of FIG. 7, FIG. 9 is a perspective view of an electrode portion showing a fourth embodiment, FIG. 10 is a perspective view of an electrode portion showing a fifth embodiment, and FIG. FIG. 12 is a perspective view of an electrode portion showing a sixth embodiment, FIG. 12 is a perspective view showing an application example of the present invention, and FIG. 13 is a system configuration diagram showing another application example. 1 ... Main laser device, 2 ... Main discharge part, 3, 4 ... Main discharge electrode,
5 ... Gas container, 6 ... Total reflection mirror, 7 ... Output mirror, 8 ... Pre-ionization laser, 9 ... Pre-ionization laser light, 10 ... Beam shaping optical system, 11, 12 ... Folding mirror, 13 ... Trigger device, 14 ... Delay device, 15 ... Corona electrode, 16 ... Spark gear cup, 17 ... Inductance for ballast, 18 ... Workpiece.

Claims (16)

[Claims] 1. A main discharge electrode arranged in a closed container in which a gas laser medium is sealed, and energy for exciting a laser gas in a discharge space by generating a discharge between the main discharge electrodes and the main discharge electrode. In a high pressure gas laser device comprising an excitation charging circuit for supplying and a preionization means for preionizing the discharge space prior to main discharge between the main discharge electrodes, wherein the high-voltage side electrode and the low voltage of the main discharge electrode A high-pressure gas laser device, wherein the side electrodes are formed in parallel with the laser optical axis and alternately arranged so as to form at least two sets of discharge parts in a layered manner. 2. A main discharge electrode arranged in a hermetically sealed container in which a gas laser medium is enclosed, and energy for exciting a laser gas in a discharge space by generating a discharge between the main discharge electrodes. In a high-pressure gas laser device comprising an excitation charging circuit for supplying and a preionization means for preionizing the discharge space prior to the main discharge between the main discharge electrodes, the preionization means, to the main discharge electrodes, A high-pressure gas laser device, which is a multi-folded laser beam having a time delay with respect to voltage application. 3. The optical axis of the multi-folded laser light is substantially orthogonal to the optical axis of the laser light formed by the main discharge,
The high pressure gas laser device according to claim 2, further comprising a folding mirror. 4. The high pressure gas laser device according to claim 3, wherein the folding mirror is coated so as to be non-reflective with respect to the laser wavelength of the main laser device. 5. The closed container is formed by a partial total reflection mirror and an output mirror, and the total reflection mirror and the output mirror are coated so as to be non-reflective with respect to the wavelength of the laser beam for preionization. The high pressure gas laser device according to claim 2, wherein 6. A main discharge electrode arranged in a hermetically sealed container in which a gas laser medium is sealed, and energy for exciting a laser gas in a discharge space by generating a discharge between the main discharge electrodes and the main discharge electrode. In a high pressure gas laser device comprising an excitation charging circuit for supplying and a preionization means for preionizing the discharge space prior to main discharge between the main discharge electrodes, wherein the high-voltage side electrode and the low voltage of the main discharge electrode The side electrodes are formed in parallel to the laser optical axis and alternately arranged so as to form at least two sets of discharge parts in a layered form, and the preionization means applies a voltage to the main discharge electrode. A high pressure gas laser device, which is a multi-folded laser beam having a time delay with respect to application. 7. A folding mirror is installed on both sides of the discharge part,
7. The high pressure gas laser device according to claim 6, wherein the multi-folded laser light for preionization intersects the optical axis of the main laser device. 8. The main discharge electrode is a porous open electrode having a large number of small holes, and a corona electrode surrounded by a dielectric is provided on the back side of the uppermost main discharge electrode. The high pressure gas laser device according to claim 1 or 6. 9. The high pressure gas laser device according to claim 1, wherein each of the discharge electrodes is formed in a mesh shape. 10. The high pressure gas laser device according to claim 1, wherein the excitation charging circuit is a pulse shaping circuit composed of an integrally molded ceramic capacitor. 11. A high-voltage side electrode and a low-voltage side electrode, which are opposed to each other at a predetermined distance in a hermetically sealed container in which a gas laser medium is sealed, and which are parallel to the laser optical axis and , Main discharge electrodes formed by alternately arranging so as to form at least two sets of discharge parts in layers, and a laser gas in the discharge space is generated by causing discharge between the main discharge electrodes, the main discharge electrodes being connected to the main discharge electrodes. Irradiating the material surface with a laser beam generated from a high-pressure gas laser device including an excitation charging circuit for supplying energy for excitation and a preionization means for preionizing the discharge space prior to the main discharge between the main discharge electrodes. A processing method using a high pressure gas laser, which is used for annealing. 12. A main discharge electrode arranged in a closed container in which a gas laser medium is sealed, and energy for exciting a laser gas in a discharge space by generating a discharge between the main discharge electrodes and the main discharge electrode. And an auxiliary charging circuit for supplying a plurality of folded laser beams having a time delay with respect to the voltage application to the main discharge electrodes in order to preionize the discharge space prior to the main discharge between the main discharge electrodes. A processing method using a high-pressure gas laser, characterized by irradiating a material surface with a laser beam generated from a high-pressure gas laser device equipped with an ionizing means and using it for annealing. 13. A high-voltage side electrode and a low-voltage side electrode which are opposed to each other at a predetermined distance in a hermetically sealed container in which a gas laser medium is sealed, and which are parallel to a laser optical axis and Main discharge electrodes formed by alternately arranging so as to form at least two sets of discharge parts in layers and connected to the main discharge electrodes to generate discharge between the main discharge electrodes to excite laser gas in the discharge space In order to pre-ionize the discharge space prior to the main discharge between the main charging electrode and the excitation charging circuit for supplying the energy, a multi-folded laser beam having a time delay with respect to the voltage application to the main discharge electrode is used. A method for processing using a high-pressure gas laser, which comprises irradiating a laser beam generated from a high-pressure gas laser device having a pre-ionization means to a material surface for annealing. 14. A laser device provided with a plurality of main laser devices arranged side by side, separately from this, with one laser device provided outside to operate the plurality of main laser devices in parallel and at the same time provided outside the laser device. A large-capacity laser system that operates as a preionization source. 15. When the laser beam generated from the high pressure gas laser device according to claim 1, 2 or 6 is applied to the surface of a plurality of materials and annealed for processing, the laser beam and the material to be irradiated are relative to each other. A processing method using a high pressure gas laser, characterized in that the moving direction is only one direction. 16. A single laser beam is applied to a single material when a plurality of material surfaces are irradiated with a laser beam generated from the high pressure gas laser device according to claim 1, 2 or 6 and annealed. A processing method using a high-pressure gas laser, characterized by irradiating and processing.