JP2718605B2 - Discharge excitation type gas laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge excitation type gas laser device such as an excimer laser device.

[0002]

2. Description of the Related Art As schematically shown in FIG. 4, a discharge excitation type gas laser device such as an excimer laser device has a gas laser vessel or gas laser tube 1 in which a laser gas is sealed. By glow discharge between the three, a laser gas is excited to generate laser light.

An excitation circuit for generating glow discharge between the main discharge electrodes 2 and 3 is generally of a so-called capacity transfer type. Excitation circuit shown in FIG. 4 is an example thereof, the charge accumulated in the charge capacitor C _1, a thyratron or a discharge gap switches such as the switching element
Is shifted to the peaking capacitor C ₂ by closing the SW, where the electrical energy stored in the peaking capacitor C ₂ becomes a predetermined amount or more, so as to cause a discharge between main discharge electrodes 2 and 3 I have.

[0004]

In such a discharge excitation type gas laser apparatus, when ArF or F ₂ is used as a component of the laser gas, a high excitation density is required, and therefore, the rise of the voltage V ₂ applied to the peaking capacitor C ₂ is increased. By increasing (dV ₂ / dt), it is necessary to increase the breakdown voltage and increase the energy stored in the peaking capacitor C ₂ .

In the excitation circuit shown in FIG. 1, dV ₂ / dt is given by the following equation.

[0006]

(Equation 1)

From this equation, L ₁ is small, or
It can be seen that C ₁ / C ₂ = 1 is a condition for fast rise of V ₂ . Here, in the formula, L ₁ is an inductance component of a circuit including the charging capacitor C ₁ , the peaking capacitor C ₂ and the switching element SW, C ₁ is the capacitance of the charging capacitor C ₁ , and C ₂ is the capacitance of the peaking capacitor C ₂ , V _HV are the voltages of the high voltage power supply.

[0008] In the prior art, by equally as possible capacitance of the charging capacitor C ₁ and the peaking capacitor C _2, the voltage applied peaking capacitor C ₂ V
It has been attempted to increase the _second rising, to charge capacitor C ₁ and the switching element SW is placed outside the gas laser tube 1, it is difficult to reduce the inductance L ₁ of the excitation circuit Was. Therefore,
In the conventional configuration, there is a limit to speed the rise of the voltage V _2, the discharge between main discharge electrodes 2 and 3 not stabilized, there is a possibility to shift from glow discharge to arc discharge.

Accordingly, an object of the present invention is to reduce the inductance of the excitation circuit, thereby speeding up the rise of the voltage applied to the peaking capacitor, increasing the breakdown voltage, and exciting the laser gas at a high density. A gas laser device is provided.

[0010]

In order to achieve the above-mentioned object, the invention according to claim 1 comprises a gas laser tube in which a laser gas is sealed, and first and second gas laser tubes arranged inside the gas laser tube so as to face each other. The electric charge charged in the main discharge electrode and the charging capacitor is transferred to the peaking capacitor by closing the switching element, and excitation is caused to cause a discharge between the main discharge electrode connected in parallel to the peaking capacitor. And a charge pump, a switching element, and a peaking capacitor of the excitation circuit are arranged in a gas laser tube.

Here, the switching element comprises a first and a second switching electrode arranged opposite to each other,
A discharge gap switch having a corona discharge electrode disposed near a first switching electrode.

Further, the gas laser device according to the present invention includes a capacitor storage tube which is disposed in the gas laser tube and is internally isolated from the laser gas, wherein the first main discharge electrode and the second switching electrode are formed of the capacitor storage tube. It is located near the outer surface. Further, the charging capacitor of the excitation circuit is disposed in the capacitor receiving tube and connected between the first main discharging electrode and the second switching electrode, while the peaking capacitors are the first and second switching electrodes. Are connected in parallel to these main discharge electrodes near the side portions of the main discharge electrodes, and a second main discharge electrode and the first switching electrode are electrically connected. I have.

According to the second aspect of the present invention, it is preferable that the second switching electrode comprises a plurality of electrode pins, in which case a charging capacitor is electrically connected to each electrode pin. Is good.

[0014]

In the present invention, since the charging capacitor, the switching element, and the peaking capacitor are arranged in the gas laser tube, the length of the wiring of the circuit composed of these can be reduced, and the inductance thereof can be reduced. it can.

As the switching element, a thyratron or a discharge gap switch capable of instantaneously switching a high voltage and a large current can be used. However, the thyratron requires a heater for emitting thermionic electrons, and when disposed in a gas laser tube, there is a problem that the laser gas is heated. Further, even in a normal discharge gap switch, an arc discharge generated between the electrodes may sputter the electrodes to generate metal powder and contaminate the inside of the laser gas tube.

Therefore, in the present invention, a discharge gap switch triggered by corona discharge is used. When a trigger is applied by corona discharge, the space between the switching electrodes is ionized in advance by corona, and the subsequent discharge is a so-called multi-arc discharge.

Here, the multi-arc discharge is a string-like arc discharge that moves around the electrode and is uniformly distributed on the electrode.
An aggregate composed of spatially uniform glow discharges, which is a discharge that is uniform between electrodes as a whole. This multi-arc discharge has a lower maximum discharge current density than a normal arc discharge, a small impact on the electrode, and the electrode is less likely to be sputtered. Further, since the bias of the discharge is small, the inductance of the switching element itself is also reduced.

Although the charging capacitor may be discharged at a lower voltage than the initial voltage by the laser gas, in the present invention, the charging capacitor is arranged in the capacitor housing tube, so that the influence of the laser gas can be prevented. Further, when the charging capacitor is arranged in the capacitor storage tube, the configuration of the present invention can greatly reduce the length of the circuit wiring.

Further, when the second switching electrode is composed of a plurality of electrode pins and a charging capacitor is connected to each of them, a multi-arc discharge is generated from each electrode pin. The transferred charge can be transferred to the first switching electrode via the corresponding electrode pin. That is, the charge from each charging capacitor is transmitted to the first switching electrode via the shortest path, and contributes to a reduction in inductance.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same or corresponding portions have the same reference characters allotted, and the upper, lower, left, and right relationships are based on the upper, lower, left, and right sides of the drawing.

FIGS. 1 and 2 show a discharge excitation type gas laser device constructed according to the present invention. 1 and 2, reference numeral 1 is a gas laser tube, the inside, the laser gas for an ArF or F ₂ as a component is enclosed in a high pressure (e.g., 21 atm). This gas laser tube 1
Is composed of a cylindrical body 1a made of aluminum and disk-shaped end plates 1b and 1c attached to seal both ends thereof.

At a substantially central portion in the gas laser tube 1, a condenser housing tube 4 made of ceramic is attached so as to extend in parallel with the longitudinal axis of the gas laser tube 1. The inside of the condenser housing tube 4 is isolated from the laser gas in the gas laser tube 1. One end of the condenser housing tube 4 penetrates the end plate 1b of the gas laser tube 1, and the inside thereof is open to the atmosphere. The other end of the condenser housing tube 4 is supported by a substantially cylindrical support member 5 penetratingly fixed to the end plate 1 c of the gas laser tube 1. A fan 6 is disposed at an outer end of the support member 5,
The atmosphere is forcibly sent into the condenser storage tube 4.

Further, a cross flow fan 7 for forcibly circulating a laser gas is provided in the gas laser tube 1.
Are arranged at positions adjacent to the condenser housing tube 4. The rotating shaft 7a of the cross flow fan 7 and the rotating shaft 6a of the fan 6 are connected to appropriate driving sources (not shown) arranged outside the gas laser tube 1, respectively.

In a lower portion of the gas laser tube 1, a pair of main discharge electrodes 2 and 3 for generating a main discharge are arranged. The main discharge electrodes 2 and 3 are long and extend parallel to the longitudinal axis of the gas laser tube 1, and the first main discharge electrode 2 serving as a negative electrode is adjacent to the outer surface of the capacitor housing tube 4. The second main discharge electrode 3 which is arranged at a position and serves as a positive electrode is opposed to the first main discharge electrode 2 at a predetermined interval.

As can be seen from FIG. 3 showing the main part of the gas laser tube 1, the first main discharge electrode 2 is attached to the lowermost portion of the capacitor housing tube 4 along the longitudinal direction thereof. It is bolted to the fixing plate 8. First fixing plate 8
Are fixed to the heads of a plurality of screw members 9 attached to the condenser housing tube 4 with bolts 10.
It is attached by being screwed into 1. Although not shown in the drawings, the through holes formed in the condenser housing tube 4 are sealed by a suitable sealing means such as a gasket.

On the other hand, the second main discharge electrode 3 is bolted on a wide second fixing plate 12 arranged in the gas laser tube 1. This fixing plate 12 is used for the gas laser tube 1.
, A support rod 14a laid between the end plate 1b and the support plate 13 fixed to the flange portion of the support member 5,
14b, it is suspended and supported by suspension metal fittings 15a, 15b.

The pumping circuit of the gas laser device according to the present invention is of the capacitance transfer type, and as described above, the charging capacitor C
_1, peaking capacitor C ₂ and the switching element S.
W.

A discharge gap switch is used as a switching element of this excitation circuit, and is arranged in an upper part in the gas laser tube 1. The discharge gap switch includes first and second switching electrodes 16 and 17, and the second switching electrode 17 is located at a position adjacent to the outer surface of the capacitor housing tube 4 and has a first main discharging electrode. It is arranged at a position opposite to the electrode 2. Further, the first switching electrode 16 is connected to the second switching electrode 1.
7, the end plate 1 of the gas laser tube 1.
It is fixed to a third fixing plate 18 laid between the support plate 13 and the support plate 13.

In this embodiment, the second switching electrode 17 is composed of a plurality of electrode pins 17a arranged in a line along the longitudinal direction of the capacitor housing tube 4. Each of the electrode pins 17a is screwed to a head of a screw member 19 attached to the uppermost part of the condenser housing tube 4. The shaft portion of the screw member 19 is inserted into a through hole of the capacitor housing tube 4 and is fixed to the capacitor housing tube 4 by a nut 20 screwed to the shaft portion.

The first switching electrode 16 has a flat plate shape and is divided into two electrode plates 16a and 16b along a center line extending in the longitudinal direction. A gap having a constant width is formed between the two divided electrode plates 16a and 16b, and a groove 21 is formed on the lower surface of the third fixing plate 18 along the gap.
Are formed. A rod-shaped corona discharge electrode 22 is arranged in the groove 21.

The corona discharge electrode 22 is inserted into a dielectric pipe 23 made of an insulating material. One end of the dielectric pipe 23 is closed, and the open end of the other end extends through the end plate 1 b of the gas laser tube 1 to the outside. The corona discharge electrode 22 is inserted to the vicinity of the closed end of the dielectric pipe 23, and a trigger power supply 24 is connected to the outer end of the corona discharge electrode 22. The electrode plates 16a,
Since the width of the gap between 16b is smaller than the outer diameter of the dielectric pipe 23, the corona discharge electrode 22 and the dielectric pipe 23 do not fall out of the groove 21 of the fixing plate 18.

The capacitor storage tube 4 houses the charging capacitor C ₁ of the excitation circuit. In this embodiment, the charging capacitor C ₁ is set to two pair, electrode pins 17
The same number of pairs as a are provided in parallel along the longitudinal direction of the condenser housing tube 4. Charging capacitor C ₁ of each set are arranged coaxially, the terminal facing each other, the corresponding electrode pins 17a
Are joined together with a conductive plate 25 extending from the fixing nut 20 therebetween. A conductive wire 26 is connected between the nuts 20. On the other hand, ends of a substantially U-shaped support plate 27 made of a conductor are screwed to the opposite terminals of each set of charging capacitors C _1.
Is screwed to the lower mating plate 11.
Screw members 9, 19, nut 20, mating plate 11, and first
Since the fixing plate 8 is made of a conductive material, so that the first main discharge electrode 2 and the second switching electrode 17 is electrically connected via a charging capacitor C _1.

The terminal (conductive plate 25) of the charging capacitor C ₁ on the second switching electrode 17 side is connected to a high-voltage power supply HV via a resistor R, and the other end of the charging capacitor C ₁ (matching plate 11) is It is grounded via a coil L ₀ of a relatively large inductance. The resistor R and the diode in the figure is provided for protection of the charging capacitor C _1.

Supports 28 are provided on both side edges of the first fixing plate 8 to which the second main discharge electrode 3 is fixed, and a plurality of peaking capacitors C ₂ are arranged on each support 28. , One terminal of which is coupled. The other terminal of the peaking capacitor C ₂ in each side are coupled to each other by a first preionization electrode 29 extending over the entire length of the main discharge electrodes 2 and 3. The discharge generating portion of the first preionization electrode 29 has a rail shape and extends to the vicinity of the space between the main discharge electrodes 2 and 3.

Since the support 28 and the second fixing plate 12 are made of a conductive material, the second main discharge electrode 3 and the peaking capacitor C ₂ are electrically connected to each other. Is a metal rectifying plate 3 for guiding the laser gas flow from the cross flow fan 7 between the main discharge electrodes 2 and 3.
0 is grounded.

Further, a support 28 supporting the peaking capacitor C ₂ is electrically connected to the first switching electrode 16. In this embodiment, a metal rectifying plate 31 spanned between the support rods 14a and 14c in the gas laser tube 1 is connected between the support rods 14c and 14b and the fixed plate 18 of the first switching electrode 16. Conductive wire 3
The first switching electrode 16 and the support 28 are electrically connected to each other by the hanging members 15 a and 15 b supporting the support 28 and the second fixing plate 12.

A second preionization electrode 34 is disposed above the discharge generating portion of the first preionization electrode 29 so as to be opposed to the first preionization electrode 29. It is fixed to. Between each of the second preionization electrodes 34 and the first main discharge electrode 2, a dielectric pipe 35 having one end closed is disposed, and a rod-shaped corona discharge electrode 36 is inserted therein. Have been. This corona discharge electrode 36
Is electrically connected to the first preliminary ionization electrode 29. Here, the shortest distance between the exposed end of the corona discharge electrode 36 and the second preliminary ionization electrode 29 is equal to the distance between the first preliminary ionization electrode 29 and the second preliminary ionization electrode 34. It is arranged at a position that is shorter than the shortest distance between them.

Next, the operation until the main discharge occurs in the gas laser device having such a configuration will be described.

Firstly, when charged to the charging capacitor C ₁ by the high voltage power source HV, the first switching element SW
A high electric field is generated between the second switching electrodes 16 and 17. When the trigger power supply 24 is turned on in a state where the charging is sufficiently performed, a discharge starts between the corona electrode 22 and the first switching electrode 16, and a creeping corona discharge is generated on the surface of the dielectric pipe 23. Occur. This corona discharge is applied to the electrode plate 1 of the first switching electrode 16.
Plasma and ultraviolet light are generated from the gap between 6a and 16b, and a part of the laser gas in the space between the first and second switching electrodes 16 and 17 is ionized. This ionization triggers a discharge between the switching electrodes 16 and 17 to be turned on.

Since a large amount of free electrons are generated in the space between the switching electrodes 16 and 17 by corona discharge, the discharge in the space is a multi-arc discharge. As described above, the multi-arc discharge refers to an aggregate of a thread-like arc discharge moving around an electrode and uniformly distributed on the electrode, and a spatially uniform glow discharge. In such a multi-arc discharge, the maximum discharge current density is significantly low, the impact applied to the electrodes 16 and 17 is small, and the consumption by discharge spatter is extremely small. Further, each electrode pin 17a than multi arcing occurs, migrate between electrodes 16 and 17 along the large amount of charge is the shortest route from the charging capacitor C _1, the inductance becomes smaller considerably in the switching element SW.

Thus, the switching electrode 1
When a multi-arc discharge occurs between the charging capacitors C1, C6, the electric charge stored in the charging capacitor C1 is transferred to the third fixed plate 18, the conductive wires 32, 33, the supporting rods 14a, 14b, 14c, the rectifying plate 31, and the hanging metal 15a. , through 15b, the process proceeds to peaking capacitor C _2. At that time, between the preionization electrodes 29 and 34 of each pair, and between the second preionization electrode 34 and the corona discharge electrode 36, substantially equal respectively, as depends on the charging capacitor C ₁ Voltage is applied.
Since the distance between the second preionization electrode 34 and the corona discharge electrode 36 is smaller than the distance between the preionization electrodes 29 and 34, the second preionization electrode 34 and the corona discharge First, discharge occurs between the electrode 36 and the electrode 36. These electrodes 34, 3
Since a dielectric pipe 35 made of an insulating material is interposed between 6, the corona discharge occurs along the surface of the dielectric pipe 35. This corona ionizes the laser gas in the space between the first and second preionization electrodes 29 and 34 to generate free electrons.

After the corona discharge, the first and second
The discharge also occurs between the pre-ionization electrodes 29 and 34. Since a large amount of free electrons are generated by the corona discharge before the discharge starts in the space between these electrodes 29 and 34, a multi-arc discharge is formed as in the case of the switching element SW. Since this multi-arc discharge occurs on a long rail-like discharge generating portion, the main discharge electrodes 2 and 3
A uniform ultraviolet light is emitted toward the space therebetween, and the laser gas in the same space is uniformly pre-ionized.

As the corona discharge and the multi-arc discharge are performed and the charge of the charging capacitor C ₁ shifts to the peaking capacitor C ₂ , the potential difference between the main discharge electrodes 2 and 3 gradually increases from zero. When this potential difference reaches the breakdown voltage between the main discharge electrodes 2 and 3, a glow discharge occurs between the main discharge electrodes 2 and 3.

As described above, the charging capacitor C ₁ , the peaking capacitor C _2, and the switching element SW of the excitation circuit of the illustrated gas laser device are arranged in the gas laser tube 1, and the length of the wiring is shortened. since the switching element SW is composed of a discharge gap switch using multi arcing, inductance L ₁ of the circuit it is greatly reduced. Therefore, the voltage V ₂ applied to the peaking capacitor C ₂ can be derived from Equation 1 above.
Rises considerably (dV ₂ / dt), the breakdown voltage between the main discharge electrodes 2 and 3 is increased, and the electric energy stored in the peaking capacitor C ₂ is increased. As a result, the laser gas can be excited at a high density, and a laser beam can be emitted with high efficiency. The laser light emitted in this manner is applied to the optical windows 37 provided on the end plates 1b and 1c of the gas laser tube 1.
a, 37b.

The above process is repeated, but the cross-flow fin 7 is always provided between the main discharge electrodes 2 and 3.
Since the undischarged laser gas is supplied and at the same time, the undischarged laser gas is also supplied between the switching electrodes 16 and 17, a high repetition operation is possible. Although the charging capacitor C ₁ generates heat by repeated operation is cooled by air fed by the fan 6, always proper operation is guaranteed.

The above embodiment shows the most conceivable structure at present, but it is needless to say that the present invention is not limited to this. For example, in the above embodiment, although the fact that accommodates the charging capacitor C ₁ to capacitor storage tube 4, if the charging capacitor C ₁ is one that is not affected by the laser gas, the capacitor storage tube 4 is not required .

Also, the second switching electrode 17 of the switching element SW is not a plurality of electrode pins, but is
A long rod-shaped or rail-shaped electrode may be used. In this case, the terminals are all charging capacitor C ₁ is connected to the rod electrode.

[0048]

As described above, according to the present invention, the charging capacitor, the peaking capacitor, and the switching element of the excitation circuit are arranged in the gas laser tube and the wiring length is shortened, so that the inductance of the circuit is greatly reduced.
Accordingly, the voltage applied to the peaking capacitor rises faster, and the breakdown voltage between the main discharge electrodes can be increased. As a result, the energy stored in the peaking capacitor increases, and the laser gas can be excited at a high density. This is particularly effective for a laser gas containing ArF or F2 as a component.

Further, by increasing the breakdown voltage between the main discharge electrodes, the discharge is stabilized, and there is no danger of changing from glow discharge to arc discharge.

Further, when the switching element is a discharge gap switch of a multi-arc discharge type, the inductance of the switching element itself can be reduced. In addition, in the case of multi-arc discharge, almost no discharge sputtering occurs, so that the switching electrode is not consumed, and therefore, the inside of the gas laser tube is not contaminated.

Conventionally, when a discharge gap switch is disposed outside a gas laser tube, a fan for circulating gas in the switch container and a drive source for the fan must be provided, which tends to increase the size of the apparatus. . However, according to the present invention, by arranging the discharge gap switch in the gas laser tube, the crossflow fan can also be used for the discharge gap switch, and the entire apparatus can be reduced in size and labor can be saved.

Further, since the switching electrode on the side connected to the charging capacitor is composed of a plurality of electrode pins, a large amount of electric charges can be transmitted, whereby the inductance can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a discharge excitation type gas laser device according to the present invention, and is a cross-sectional view taken along line BB of FIG.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a perspective view showing a main part inside a gas laser tube in the gas laser device of FIG. 1;

FIG. 4 is a schematic diagram of a conventional discharge excitation type gas laser device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Gas laser tube, 2 ... 1st main discharge electrode, 3 ... 2nd
Electrodes for main discharge, 4 ... condenser housing tube, 7 ... cross flow fan, 16 ... first switching electrode, 17 ...
2nd switching electrode, 17a ... electrode pin, 22 ...
Corona discharge electrode, 23: dielectric pipe, 24: trigger power supply, C ₁ : charging capacitor, C ₂ : peaking capacitor, SW: switching element.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-206787 (JP, A) JP-A-4-67973 (JP, A) JP-A-1-128387 (JP, A)

Claims (2)

(57) [Claims] A gas laser tube in which a laser gas is sealed; first and second main discharge electrodes disposed in the gas laser tube so as to face each other; a charging capacitor disposed in the gas laser tube; A switching element disposed in the tube; and a peaking capacitor disposed in the gas laser tube. The charge charged in the charging capacitor is transferred to the peaking capacitor by closing the switching element, and the peaking is performed. A discharge excitation type gas laser device comprising an excitation circuit for generating a discharge between the main discharge electrodes connected in parallel to a capacitor, wherein the first and second switching elements are arranged to face each other. And a second switching electrode and a first switching electrode. A discharge gap switch having a corona discharge electrode, a capacitor housing tube disposed in the gas laser tube and internally isolated from the laser gas, the first main discharge electrode and the second switching electrode. An electrode is arranged near an outer surface of the capacitor housing tube, and the charging capacitor is arranged in the capacitor housing tube, and is connected between the first main discharge electrode and the second switching electrode. Wherein the peaking capacitor is connected in parallel to the first and second main discharge electrodes in the vicinity of side portions of the first and second main discharge electrodes, and the second main discharge electrode and the first switching electrode Are electrically connected to each other. 2. The discharge-excited gas laser according to claim 1, wherein the second switching electrode includes a plurality of electrode pins, and the charging capacitor is electrically connected to each of the electrode pins. apparatus.