JPH088481A - Laser gas control device for discharge excitation type laser device - Google Patents

Abstract

PURPOSE:To compensate a discharge excitation-type laser device for variation in output high in controllability by a method wherein laser gas is controlled in supply or in exhaust so as to make the power of an outputted laser beam equal to an output power target when it is detected by a power detecting means that the power of an outputted laser beam gets out of an output target or a range of output target. CONSTITUTION:An outputted laser beam La is inputted into an optical output detector 15, and a laser output E is detected by the optical output detector 15 and inputted into a controller 3. The controller 3 carries out a procedure that a gaseous pressure P is increased or reduced comparing a command charging voltage Va (current charging voltage V) with a maximum voltage Vmax and a minimum voltage Vmin in a charging voltage control range so as to keep a laser output stable. Therefore, even if a charge/discharge circuit equipped with a magnetic switch is applied to a discharge excitation-type laser device, the device can be compensated for variation in laser output with high controllability.

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 laser device used as a light source for processing materials, reducing projection exposure, and the like, and more particularly to a device for controlling the supply of a laser gas.

[0002]

2. Description of the Related Art A discharge-excited laser device is used as a light source for photolithography for material processing such as marking, drilling and annealing, and for producing a circuit pattern of a large scale integrated circuit (LSI).

[0003] Among gas lasers, an excimer laser is a powerful ultraviolet light source, and is used mainly for marking and drilling an organic material such as a resin for material processing by utilizing its characteristics. In optical lithography, the reduction projection method is mainly used, and the transmitted light of an original image (reticle) pattern illuminated by an illumination light source is projected onto a photosensitive material on a semiconductor substrate by a reduction projection optical system. Form a circuit pattern.

Since the resolution of this projected image is limited by the wavelength of the light source used, the wavelength of the light source is gradually shortened from the visible region to the ultraviolet region. Conventionally, g-line (43) generated from a high pressure mercury lamp has been used as a light source in the ultraviolet region.
6 nm), i-line (365 nm) has been used. However, when the minimum pattern line width is 0.35 μm or less required for 64 MB, the wavelength of the i-line is almost at its limit.

As a solution to this technical limitation, a deep ultra violet laser light source is expected. In particular, excimer lasers have high output,
KrF (248 nm) depending on the composition of the medium gas with high efficiency,
Strong oscillation can be obtained at a wavelength such as ArF (193 nm). On the other hand, in the Deep-UV region, it is difficult to correct the chromatic aberration that has been used in the reduction projection lens system using the mercury lamp, because the glass and the crystal material forming the reduction projection lens system are very limited.

Therefore, instead of correcting the lens system for chromatic aberration, a wavelength selecting element is provided in the laser resonator, and the spectral width of the output light is reduced to such an extent that the chromatic aberration of the lens material can be ignored. Has been removed. With this method, the output which was several nm in the spectrum width in the case of natural oscillation can be narrowed to a few pm and the band can be narrowed. Now, the output (power) of the laser of the excimer laser device, which is suitable for narrowing the band in this way, is that the electric energy stored in the capacitor for exciting the laser is injected into the discharge space and the laser medium gas It is obtained by discharging at.

FIG. 15 shows a structure of a conventional excimer laser device, and FIG. 16 shows a charge / discharge circuit particularly. As the charge / discharge circuit, an automatic preionization type capacity transfer type circuit is generally used because of its simple structure.

That is, the primary capacitor C1 for storage is charged to a predetermined voltage by the charger, and thereafter, the switch element Q, which is energized by thyratron or the like discharge, is turned on by the trigger pulse output from the trigger pulse generator 25. Then, charging (charge transfer) to the secondary capacitor (peaking capacitor) C2 is started. At the time of this charge transfer, the charging current i1 is applied to dozens of preliminary ionization electrodes 6 arranged on both side surfaces of the main electrode (laser chamber discharge electrode) 5. At this time, a preliminary ionization discharge is generated,
Automatic preionization is performed.

The discharge space is irradiated with the ultraviolet light generated by such preliminary ionization discharge, and initial electrons are generated in the main discharge space. When the voltage of the secondary capacitor C2 reaches the discharge starting voltage, a main discharge occurs, a population inversion is formed in the laser medium, and laser oscillation is generated.

In the laser chamber 4, a heat exchanger 7 and a laser medium gas (hereinafter referred to as "laser gas") are provided.
Blower 8 for forced convection and cooling is incorporated,
It enables operation at high repetition frequencies of tens to hundreds of Hz. In addition, in order to stabilize the laser output during operation, the laser output is monitored by an optical sensor, and the charging voltage is changed based on the monitoring result to deteriorate the laser gas.
The output stabilization control is performed so that the output does not decrease due to stains on the window.

The discharge switch Q typified by a thyratron used in a conventional laser device may lose durability due to consumption of electrodes due to evaporation and consumption of heaters necessary for operation. There are obstacles in terms of.

That is, as shown in FIG. 17, when the conduction resistance R (turn-on resistance) when the thyratron Q shifts from the off state to the on state is high, a large current i1 is generated.
Causes a large thyratron loss (Ohm loss (i1) 2.R; (i1) 2 means the square of i1), which is indicated by oblique lines. At the same time, thyratron Q is consumed. It is thought that there is.

Therefore, in order to suppress the conduction current when there is a high turn-on resistance immediately after such switching, a charge / discharge circuit using a saturable reactor as a magnetic switch is used. This type of technology is described in, for example, Hitachi Metals Technical Report vol. 8 1992.1
It is described in "Dynamic characteristics of magnetic core for pulse power magnetic switch using Finemet".

The saturable reactor used as a magnetic switch is an element utilizing the saturation phenomenon of the magnetic flux of a magnetic material, and Fe-based or Co-based amorphous winding magnetic cores with an interlayer insulation and Fe-based ultrafine crystalline magnetic alloy (Hitachi) Magnetic cores using the metal trademark "Finemet") are used.

Here, the operation when a magnetic pulse compression circuit, which is a typical system of a circuit using a magnetic switch, is applied to a pulse power supply of a pulse laser will be described with reference to FIG.

In FIG. 18, when the magnetic switch SR is designed to saturate when all the charges stored in the capacitor C1 are transferred to C2 under the condition of C1 = C2 = C3, The transferred charge is most efficiently transferred to the capacitor C3. FIG. 19 shows the voltage and current waveforms of the main parts when this condition is satisfied.

After the main switch Q is turned on, τ1 is the period until all the charges accumulated in the main capacitor C1 are transferred to the capacitor C2. During the period of τ1, the operating point of the magnetic core is in the unsaturated region on the loop of FIG. 14, and moves from the point a to the point b over time. At this time, since the magnetic permeability μrs of the magnetic core of the magnetic switch SR is very high, the inductance LSRu of the output winding N is sufficiently larger than the inductance L1, and almost no current flows through the output winding N. Therefore, the magnetic switch SR blocks the current during the voltage-time product indicated by the hatched portion in FIG. 19, and the following equation holds.

[0018] vsr: Voltage applied to the magnetic core N: Number of turns of the magnetic switch Ae: Effective area of the magnetic core ΔBm: Maximum operating magnetic flux density Here, the time width τ1 of the current pulse after turn-on is given by the following equation.

Τ1 = π√ (L1C1C2 / (C1 + C2)) (2) When the operating point of the magnetic core reaches point b on the loop in FIG. 14 and then moves to point d via point c The core is saturated, and the magnetic permeability μrs of the magnetic core is almost equal to the magnetic permeability μ0 of vacuum. At this time, the inductance LSRs is the inductance L1
Most of the electric charge transferred to the capacitor C2 is sufficiently smaller and transferred to the capacitor C3 with the pulse width τ2 shown in FIG.

Τ2 = π√ (LSRsC2C3 / (C2 + C3)) (3) When the direction of the transfer current i2 is reversed, the operating point of the magnetic core is as shown in FIG.
Although it moves from point d on the loop of No. 4 to point a, it surely moves toward point a. Here, the ratio between τ1 and τ2 is called a compression gain Gc, and has the following relationship.

Gc = τ1 / τ2 = I2m / I1m (4) I1m: peak value of i1 I2m: peak value of i2 By using the magnetic pulse compression circuit as described above, the main switch Q can be used as compared with the case where it is not used. The pulse width and peak value of the flowing current can be made Gc times and 1 / Gc times respectively. Therefore, the switching loss of the main switch Q can be reduced, and high output and high repetition can be achieved. Further, it becomes possible to use a semiconductor switch element having a maximum forward resistance and a long turn-on time as compared with a discharge switch such as a thyratron. Since the magnetic switch essentially has no consumable part, a highly durable pulse power supply requiring no maintenance can be realized by combining the magnetic switch with a semiconductor switch.

[0022]

The charging / discharging circuit using the magnetic switch has the advantages as described above, but has the following essential problems and is difficult to apply to a practical machine. , Could not be put to practical use.

That is, as described above, the current blocking time τ1 of the compression element (saturable reactor) in the magnetic compression circuit changes depending on the voltage vsr applied to the magnetic core as shown in the above equation (1). Therefore, when the output of the laser beam is fed back to control the charge voltage to be changed as in the related art, there is a problem that the stop time of the saturable reactor is changed.

More specifically, in the case of a gas laser such as an excimer laser, an impurity gas is generated in the laser gas, a component gas is consumed, and a window for extracting light is contaminated as the operation proceeds. As a result, the oscillation efficiency decreases, and the laser output decreases. Therefore, conventionally, in order to compensate for this output decrease and obtain a constant output, the operating voltage (charging voltage) is increased to stabilize the output.

However, when the magnetic compression circuit is used, when the operating voltage is increased, the current blocking time is shortened, the compression timing is shifted, the energy transfer efficiency is deteriorated, and the laser output is reduced. Would. That is, as shown in FIG.
Assuming that the maximum value and the minimum value of the voltage at which the efficiency is そ の are Vmax and Vmin, respectively, this range Vm
If it exceeds (Vmin to Vmax), practicality is almost lost in terms of energy efficiency. Therefore, there is an optimum operating voltage range of Vmin to Vmax,
It is necessary to perform voltage control that maintains this voltage range. Conversely, since a narrow voltage range must be maintained, voltage controllability is poor. This has been an obstacle to applying a charge / discharge circuit using a magnetic switch to a laser device and putting it into practical use.

The present invention has been made in view of these circumstances, and even when a charge / discharge circuit having a magnetic switch is applied to a discharge excitation type laser device, compensation for laser output fluctuation is controlled. It is an object of the present invention to provide an apparatus which can be well operated and can easily perform laser output stabilization control.

[0027]

Therefore, in the main invention of the present invention, a power supply, a main switch for applying a voltage of the power supply to a discharge electrode, and a main switch interposed between the main switch and the discharge electrode, In a laser chamber in which a charging / discharging circuit having a magnetic switch for blocking a current flowing from the power source to the discharge electrode for a time period according to the magnitude of the voltage of the power source is provided and in which the discharge electrode is arranged. In the discharge excitation type laser device, which supplies the laser gas to excite the laser gas by the discharge between the discharge electrodes, and oscillates and outputs the laser light, a power detection unit that detects the power of the output laser light, When the power detection unit detects that the power of the output laser light deviates from the target value or the target range, the power of the output laser light is The supply amount of the laser gas supplied into the laser chamber or the exhaust of the laser gas discharged from the laser chamber while maintaining the voltage of the power supply at a constant value so as to match the standard value or fall within the target range. And control means for controlling the quantity.

Here, the power detecting means may directly detect the optical power, and indirectly detects the optical power by detecting a parameter related to the optical power such as a halogen gas concentration and a rare gas concentration. It may be one that does.

[0029]

According to this structure, when the power detection means detects that the power of the output laser light deviates from the target value or the target range, the power of the output laser light matches the target value or the target range. The amount of laser gas supplied into the laser chamber or the amount of laser gas exhausted from the laser chamber is controlled while the voltage of the power supply is maintained at a constant value. In this way, the fluctuation of the laser output is compensated with good controllability only by controlling the laser gas supply / exhaust without voltage control.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a laser gas control device of a discharge excitation laser device according to the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 shows the configuration of a laser device according to a first embodiment. The same components as those of the conventional device are denoted by the same reference numerals, and the description of the contents already described is omitted.

As shown in the figure, the apparatus of the embodiment is mainly composed of a charge / discharge circuit 1 for performing a discharge between the main electrodes 5 and 5, a laser gas supplied and filled, and a discharge between the main electrodes 5 and 5. As shown in FIG. 10, which will be described later, a laser chamber 4 in which laser gas is excited and laser light La is oscillated, a laser gas is supplied to the laser chamber 4, and a laser gas is exhausted from the chamber 4. And a controller 3 for controlling the charge / discharge circuit 1 and the supply / exhaust circuit 2 based on the output of the pressure sensor 13 and the like.

That is, the rare gas cylinder 9 is filled with a rare gas (Xe, Kr, Ar, etc.), and the halogen gas cylinder 10 is filled with a halogen gas (a gas obtained by diluting F2, HCl, etc. with a buffer gas). The buffer gas cylinder 11 is filled with a buffer gas (He, Ne, etc.). A pipe is provided between each of the cylinders 9, 10, 11 and the laser chamber 4 via each of the valves 14a to 14f and the exhaust pump 12, and a valve opening / closing signal is sent from the controller 3 to each of the valves 14a to 14f. The output of S1 and the output of the pump drive signal S2 to the exhaust pump 12 control the supply of the laser gas to the laser chamber 4 and the exhaust of gas from the chamber 4.

The pressure sensor 13 detects the gas pressure P in the laser chamber 4 and inputs the detected output P to the controller 3.

Laser gas is discharge-excited in the laser chamber 4, and light emitted thereby is resonated by a resonator (not shown), so that laser oscillation is performed. The oscillation laser light La is output through a window, a front mirror, and the like (not shown).

The output laser beam La is input to the optical output detector 15, the laser output (power) E is detected by the optical output detector 15, and the detected output E is detected by the controller 3.
Is input to The optical output detector 15 detects the laser output E by holding the peak value of the pin photodiode, for example. The light output detector 15 may be one that directly detects the light power, and indirectly detects the light power by detecting a parameter related to the light power such as a halogen gas concentration and a rare gas concentration. It may be one.

Further, a counter (not shown) for counting light every time light is detected by the light output detector 15 is provided. The oscillation pulse number N of the laser light La is counted by this counter, and the output N of this counter is input to the controller 3.

The charging / discharging circuit 1 discharges between the main electrodes 5 and 5 by using the DC high voltage power supply 17 as a driving source. This power supply 1
The charging voltage V of 7 is also detected by a voltage detector (not shown) and input to the controller 3.

The controller 3 includes a laser output E detected by the optical output detector 15, a gas pressure P detected by the pressure sensor 13, a count number N detected by the pulse counter, and a power supply 17 detected by the voltage detector. A command voltage Va is output to the power supply 17 based on the charging voltage V, and the charging voltage is controlled so that the charging voltage V of the power supply 17 becomes the commanded voltage value Va.

The charge / discharge circuit 1 operates when a thyristor 18 as a main switch provided with a magnetic assist 19 is turned on. The controller 3 sends a drive signal S3 for operating the charge / discharge circuit 1 to the drive circuit 16, and in response to this, the drive circuit 16 sends an ON signal S4 to the main switch 18
, The charge / discharge circuit 1 operates.

Although the main switch 18 uses a thyristor, other semiconductor switches such as GTO and IG are used.
BT can also be used.

The charge / discharge circuit 1 is a two-stage magnetic compression circuit having a pulse transformer 20, that is, a magnetic switch SR having two stages.
It has a complete circuit configuration.

At the start of operation of the laser apparatus, first, the vacuum pump evacuates the gas to a predetermined gas pressure,
The old gas in the laser chamber 4 is exhausted. Next, the valves 14a ... Are opened and closed as required, and the output P of the pressure sensor 13 is output.
Until a predetermined value is reached, each of a rare gas, a halogen gas and a buffer gas is sequentially injected.

After the laser gas is injected into the chamber 4, sequential control such as activation of the gas circulation blower 8 in the chamber 4 and warming up of the power supply 17 is sequentially executed, and the laser device is sequentially executed. Is ready for operation. Therefore, prior to the operation of the laser apparatus, first, as shown in step 101 of FIG. 10, the target laser output Ec, the halogen gas injection pulse number interval Nc, the charging voltage change ΔV, and the 1
The replenishment gas amount ΔG1, the replenishment gas amount ΔG2 for the halogen gas, the replenishment gas amount ΔG3 for the buffer gas, the exhaust gas amount ΔG4 for one exhaust gas, and the limit gas pressures (Pmax, Pmin) are preset. At the same time, the pulse number counter is reset (N = 0).

Thereafter, when the operation of the laser device is started, the laser output E detected by the optical output detector 15, the chamber pressure P detected by the pressure sensor 13, and the charging voltage V detected by the voltage detector are detected. Are sequentially taken into the controller 3. However, the charging voltage V can be substituted by the command voltage Va (step 10).
2).

The controller 3 compares the detected laser output E with the target laser output Ec (step 103), and if E <Ec, increases the charging voltage V by the minute voltage ΔV to obtain the command charging voltage Va ( If E = Ec, the detected voltage V is directly used as the command charging voltage Va (step 104). If E> Ec, the detected charging voltage V is lowered by the minute voltage ΔV to become the command charging voltage Va. (Step 106).

In general, when performing control to approach the target value, a dead zone is provided in consideration of the resolution of the detector and various noises. Therefore, the target laser output Ec
May have a certain width. That is, a target range may be set and control may be performed such that the laser output falls within this target range.

Further, the controller 3 controls the command charging voltage V
a (current charging voltage V) is compared with the maximum value Vmax and the minimum value Vmin of the charging voltage control range Vm (step 107),
If Va ≦ Vmax and Va ≧ Vmin, the process proceeds to the next step 111 while maintaining the gas pressure P at the current pressure (step 108).

However, if the command charging voltage Va is Va> Vmax
In case of, a rare gas cylinder 9 and a buffer gas cylinder 1
The process of replenishing the predetermined amount of the rare gas ΔG1 and the buffer gas ΔG3 from 1 to the laser chamber 4 is performed, and the gas pressure P is increased by a minute amount ΔP, and then the process proceeds to step 111 (step 110). When Va <Vmin, the laser gas in the laser chamber 4 is exhausted by a predetermined amount ΔG4, the gas pressure P is reduced by a minute amount ΔP, and then the process proceeds to step 111 (step 10).
9).

Normally, laser output tends to decrease due to generation of impurity gas and fouling of windows and the like, and the exhaust pressure step can be omitted in many cases because the total pressure increases with gas supply. Therefore, the process of step 109 may be omitted.

During operation of the laser device, control for replenishing halogen gas is also performed (steps 113 to 11).
6).

That is, during the operation of the laser apparatus, the halogen gas decreases due to the reaction with the electrode evaporant and the like, and the amount of the decrease is proportional to the operation time, that is, the number N of operation pulses. Therefore, in order to replenish the halogen gas in an amount proportional to the operation pulse number N, the count pulse number N is set to a predetermined value N
Every time the temperature reaches c, the halogen gas is replenished by a predetermined amount ΔG 2. Then, when the supply of the halogen gas is performed, the count value N is reset to zero, and the process proceeds to step 111, which is the next process (steps 114, 115, 1).
16). In this embodiment, the pulse number N is obtained by counting the detection signal of the optical output detector 15, but it may be obtained by counting the trigger signal which is an oscillation command.

In step 111, it is determined whether or not the gas pressure P in the laser chamber 4 is within a predetermined range Pmin ≦ P ≦ Pmax. If the gas pressure P exceeds this range, the laser output E is maintained. Therefore, an abnormal process such as a required alarm display or an error process such as the output of a service request signal for gas replacement or replacement of a deteriorated part is performed (step 112).

In this embodiment, the charging voltage V is controlled so as to fall within the charging voltage control range Vm. However, only the supply and exhaust control of the laser gas may be performed while keeping the charging voltage constant. .

In this case, the processes of steps 108 to 110 are performed after the process of step 103 (instead of the processes of steps 104 to 106), and then step 111.
Will be moved to.

That is, the controller 3 detects the detection laser output E
Is compared with the target laser output Ec (step 103).
If <Ec, a process of exhausting the laser gas in the laser chamber 4 by a predetermined amount ΔG4 is performed (step 10).
9) If E = Ec, the gas pressure P is maintained at the current pressure (step 108). If E> Ec, predetermined amounts of the rare gas ΔG1 and the buffer gas ΔG3 are supplied from the rare gas cylinder 9 and the buffer gas cylinder 11. Is performed in the laser chamber 4 (step 110).

Further, in this embodiment, the process of replenishing the halogen gas at regular intervals (steps 113 to 116) is performed, but this may be omitted depending on the case. Further, the replenishment of the halogen gas may be performed together with the replenishment of the other rare gas and the buffer gas in step 110.

In this embodiment, the charging voltage V is directly detected. However, since the charging voltage V and the beam width Δw of the laser light La are in a substantially proportional relationship, the charging is performed by detecting the beam width Δw. The voltage V may be detected. Here, the beam width Δw means a width in a direction perpendicular to the discharge direction between the main electrodes 5 and 5, as shown in FIG.
It can be detected by transferring the laser light onto the line sensor.

Further, since the relationship between the charging voltage V and the spectral width Δλ in the frequency spectrum distribution of the laser light La, for example, the half value width, is also in a substantially proportional relationship, the charging voltage V is detected by detecting the spectral width Δλ. You may do it.

It is also possible to use the charging / discharging circuit 1 shown in FIGS. 2 to 7 instead of the charging / discharging circuit 1 shown in the first embodiment.

FIG. 2 shows a thyratron 1 as a main switch.
8 shows a second embodiment to which a two-stage magnetic compression circuit adopting 8'is applied.

FIG. 3 shows a third embodiment in which a one-stage magnetic compression circuit using a saturable transformer 20 'instead of the pulse transformer 20 is applied.

FIGS. 4 and 5 show fourth and fifth embodiments to which a two-stage magnetic compression circuit using a saturable transformer 20 'is applied.

FIG. 6 shows a sixth embodiment in which one-stage magnetic compression circuit is added to the voltage doubler circuit 21 by LC inversion.

FIG. 7 shows a seventh embodiment in which a two-stage magnetic compression circuit is added to the voltage doubler circuit 21 by LC inversion.

Now, FIG. 8 shows the structure of an eighth embodiment device to which the charging / discharging circuit 1 having the same circuit structure as that of FIG. 1 is applied. What is different from FIG. 1 is the frequency spectrum of the laser beam La. Spectral width Δλ in distribution (for example, full width at half maximum)
This is the point where a spectrum width detector 22 for detecting is added. The detection output Δλ of the spectrum width detector 22 is input to the controller 3 and the processing shown in FIG. 11 is performed.

Hereinafter, the processing performed by the controller 3 will be described with reference to FIG. Note that the description of the processing content that is the same as the processing of FIG. 10 will be omitted.

First, in step 201, the same processing as in step 101 is performed, and the setting of the target spectrum width Δλc is also performed.

In the next step 202, the same processing as in step 102 is executed, and the spectrum width Δλ detected by the spectrum width detector 22 is sequentially fetched by the controller 3 (step 202).

Then, step 203 to step 210
Then, the charging voltage control and the gas supply / exhaust control are executed in the same manner as in steps 103 to 110. Also, in steps 213 to 216, the above-described step 11
Similar to 3 to step 116, a periodical halogen gas supply process is executed.

Then, in steps 217 to 220 after the halogen gas replenishment process is completed, the spectrum width stabilization control is executed.

That is, the narrow band excimer laser using the angular dispersion type narrow band element has a characteristic that the spectral profile, that is, the spectral width, changes according to the laser gain distribution in the dispersion angle direction. And, the fact that the composition of the laser gas, particularly the partial pressure of the halogen gas, and the spectral profile have a strong dependence has been disclosed in the present application of the present inventors (Japanese Patent Application No. Hei.
-312202). Therefore, in the eighth embodiment, the supply amount ΔG2 of the halogen gas is increased or decreased according to the output of the spectrum width detector 22 to stabilize the halogen partial pressure, thereby stabilizing the spectrum width Δλ.

First, the detected spectrum width Δλ is compared with the target spectrum width Δλc (step 217), and Δλ <Δ
If λc, the halogen gas replenishment amount ΔG2 is a minute amount dG2
And the supply amount ΔG2 is updated (step 22)
0), if Δλ = Δλc, the current halogen gas replenishment amount ΔG2 is updated without changing the present replenishment amount ΔG2 (step 218). If Δλ> Δλc, the halogen gas replenishment amount ΔG2 is obtained. Is reduced by a minute amount dG2 to update the replenishment amount ΔG2 (step 219). After that, the procedure moves to step 211, and the gas pressure comparison processing and abnormality processing similar to those in steps 111 and 112 are executed (steps 211 and 212).

FIG. 9 shows the configuration of a ninth embodiment to which the charging / discharging circuit 1 having the same circuit configuration as that of FIG. 1 is applied. The difference from FIG. The point is that a beam profile detector 23 for detecting a beam width Δw in a direction perpendicular to the discharge direction is added. The beam profile detector 23 detects the beam width Δw by transferring the laser beam La onto a line sensor. The detection output Δw of the profile detector 23 is input to the controller 3 and the processing shown in FIG. 12 is performed.

The contents of processing performed by the controller 3 will be described below with reference to FIG. Note that the description of the processing content that is the same as the processing of FIG. 10 will be omitted.

First, in step 301, the same processing as in step 101 is performed, and the setting of the target beam width Δwc is also performed.

In the next step 302, the same processing as in step 102 is executed, and the beam width Δw detected by the beam width detector 23 is sequentially fetched by the controller 3 (step 302).

Then, steps 303 to 310
Then, the charging voltage control and the gas supply / exhaust control are executed in the same manner as in steps 103 to 110. In step 313 to step 316, the above step 11
Similar to 3 to step 116, a periodical halogen gas supply process is executed.

Then, in steps 317 to 320 after the halogen gas supply processing is completed, beam width stabilization control is executed.

That is, the excimer laser has a beam profile, that is, a beam width Δw according to the laser gain distribution.
Change. The inventors have found that the gas composition, especially the partial pressure of the halogen gas, strongly depends on the beam profile, and it is also shown in Japanese Patent Application No. 6-73389, which has already been filed.
Therefore, the supply amount ΔG2 of the halogen gas is increased or decreased in accordance with the detection output of the beam profile detector 23 to stabilize the partial pressure of the halogen gas, thereby stabilizing the beam width, that is, the profile.

First, the detected beam width Δw is equal to the target beam width Δ
is compared with wc (step 317). If .DELTA.w <.DELTA.wc, the supply amount .DELTA.G2 of the halogen gas is increased by a small amount dG2, and the supply amount .DELTA.G2 is updated (step 320).
= Δwc, the current halogen gas replenishment amount ΔG2 is updated without changing the present replenishment amount ΔG2 (step 318). If Δw> Δwc, the halogen gas replenishment amount ΔG2 is set to a minute amount dG2. Just lower the supply amount Δ
G2 is updated (step 319). After that, the procedure moves to Step 311, and the above Steps 111 and 11 are performed.
Gas pressure comparison processing and abnormality processing similar to those in 2 are executed (steps 311 and 312).

[0082]

As described above, according to the present invention, the voltage of the power supply is maintained at a constant value or the voltage is controlled so that the power of the output laser light becomes a target value. Since the supply / exhaust amount of the laser gas is controlled while controlling, even when the charging / discharging circuit having the magnetic switch is applied to the discharge excitation type laser device,
The laser output fluctuation can be compensated with good controllability. Therefore, by adopting the charging / discharging circuit having the magnetic switch, the durability of the electrodes and the like can be improved, and the laser output can be easily stabilized by the controllability.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of a laser gas control device of a discharge excitation type laser device according to the present invention.

FIG. 2 is a diagram showing a configuration of a second embodiment.

FIG. 3 is a diagram showing a configuration of a third exemplary embodiment.

FIG. 4 is a diagram showing a configuration of a fourth embodiment.

FIG. 5 is a diagram showing a configuration of a fifth embodiment.

FIG. 6 is a diagram showing a configuration of a sixth embodiment.

FIG. 7 is a diagram showing a configuration of a seventh embodiment.

FIG. 8 is a diagram showing a configuration of an eighth embodiment.

FIG. 9 is a diagram showing a configuration of a ninth embodiment.

FIG. 10 is a flowchart illustrating a processing procedure according to the first to seventh embodiments.

FIG. 11 is a flowchart illustrating a processing procedure according to an eighth embodiment;

FIG. 12 is a flowchart showing a processing procedure of a ninth embodiment.

FIG. 13 is a graph showing a relationship between normalized operating voltage and energy transfer efficiency when a magnetic compression circuit is used.

FIG. 14 is a graph showing the operation of the magnetic switch magnetic core.

FIG. 15 is a diagram showing a configuration of a conventional laser device.

FIG. 16 is a circuit diagram showing a configuration of a charge / discharge circuit of a conventional laser device.

FIG. 17 is a graph showing waveforms of a voltage and a current of a main switch in the circuit of FIG. 16;

FIG. 18 is a circuit diagram showing a magnetic compression circuit.

19 is a graph showing voltage and current waveforms at various parts of the magnetic compression circuit of FIG. 18.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charge / discharge circuit 2 Supply / exhaust circuit 3 Controller 4 Laser chamber 5 Main electrode SR Magnetic switch 15 Optical output detector 17 DC high voltage power supply

Claims (4)

[Claims] 1. A power source, a main switch for applying a voltage of the power source to a discharge electrode, and a current flowing from the power source to the discharge electrode, which is interposed between the main switch and the discharge electrode. A charging / discharging circuit having a magnetic switch for blocking for a time corresponding to the magnitude of the voltage is provided, and a laser gas is supplied into the laser chamber in which the discharging electrodes are arranged to discharge the discharge electrodes. In a discharge excitation type laser device that excites the laser gas and oscillates and outputs laser light, a power detection unit that detects the power of the output laser light, and the power of the output laser light is the target by the power detection unit. When the value or the deviation from the target range is detected, the power of the output laser light matches the target value or falls within the target range, In a discharge excitation type laser device, comprising: a control means for controlling the supply amount of the laser gas supplied into the laser chamber or the exhaust amount of the laser gas discharged from the laser chamber while maintaining the voltage of the power supply at a constant value. Laser gas control device. 2. A power supply, a main switch for applying a voltage of the power supply to a discharge electrode, and a current flowing from the power supply to the discharge electrode, which is interposed between the main switch and the discharge electrode. A charging / discharging circuit having a magnetic switch for blocking for a time corresponding to the magnitude of the voltage is provided, and a laser gas is supplied into the laser chamber in which the discharging electrodes are arranged to discharge the discharge electrodes. In a discharge excitation type laser device that excites the laser gas and oscillates and outputs laser light, a power detection unit that detects the power of the output laser light, and the power of the output laser light is the target by the power detection unit. When the value or the deviation from the target range is detected, the power of the output laser light matches the target value or falls within the target range, The voltage control means for changing the voltage of the power supply and the voltage adjustment range of the power supply are set in advance, and when the voltage of the power supply is changed by the voltage control means, the voltage is out of the voltage adjustment range. A supply / exhaust control means for controlling the supply amount of the laser gas supplied into the laser chamber or the exhaust amount of the laser gas discharged from the laser chamber so that the voltage of the power supply falls within the voltage adjustment range. A laser gas control device in the discharge excitation type laser device. 3. A spectrum width detecting means for detecting a spectrum width in a frequency spectrum distribution of output laser light, wherein the spectrum width detecting means detects the spectrum width from a target spectrum width when the spectrum width is detected. The laser gas is supplied into the laser chamber or discharged from the laser chamber so that the width becomes a target spectral width.
Alternatively, a laser gas control device in the discharge excitation type laser device according to the second aspect. 4. A beam width detecting means for detecting a beam width in a direction substantially perpendicular to a discharge direction between discharge electrodes, wherein the beam width detecting means detects that the beam width deviates from a target beam width. And controlling the supply of the laser gas into the laser chamber so that the beam width becomes the target beam width or the discharge of the laser gas from the laser chamber. Control device.