JP4429042B2 - Two-stage laser device with high-accuracy synchronous control function - Google Patents

Description

  The present invention relates to a two-stage ArF excimer laser device for exposure, which is an exposure light source for improving the throughput of an exposure device and enabling ultrafine processing by exposure.

With the miniaturization and high integration of semiconductor integrated circuits, improvement in resolving power is demanded in the projection exposure apparatus for production. For this reason, the wavelength of the exposure light emitted from the exposure light source is being shortened, and a KrF excimer laser device having a wavelength of 248 nm from a conventional mercury lamp is used as a light source for semiconductor exposure. Further, as a next-generation light source for semiconductor exposure, gas laser devices that emit ultraviolet rays, such as an ArF excimer laser device having a wavelength of 193 nm and a fluorine molecule (F ₂ ) laser device having a wavelength of 157 nm, are promising.
A pair of main discharge electrodes for exciting the laser gas are disposed opposite to each other at a predetermined distance in a direction perpendicular to the laser oscillation direction in a laser chamber in which a laser gas as a laser medium is sealed. A high voltage pulse is applied to the pair of main discharge electrodes, and when the voltage applied between the main discharge electrodes reaches a certain value (breakdown voltage), the laser gas between the main discharge electrodes breaks down and main discharge starts. The laser medium is excited by this main discharge. Therefore, such an exposure gas laser apparatus performs pulse oscillation by repeating main discharge, and the emitted laser light becomes pulse light. When applied as a light source to an exposure apparatus using a projection optical system, the spectral line width of the laser light emitted from the gas laser apparatus as described above is narrowed to avoid the problem of chromatic aberration in the projection optical system. The
For example, the laser resonator includes an output mirror that sandwiches a laser chamber and a narrow-band optical system. The band-narrowing optical system [LNM (Line Narrow Module)] includes, for example, a magnifying optical system including a slit, a magnifying prism, and a reflective grating from the side on which the laser beam is incident.

In recent years, from the viewpoint of improving throughput and further miniaturization, it has been required to increase the laser output of the above-described exposure gas laser apparatus and to narrow the spectral line width of laser light.
In order to increase the output, which is the first requirement, there are a method of increasing the energy per pulse, or a method of increasing the repetition frequency with a low pulse energy.
As described above, the ultra-narrow band, which is the second requirement, is to increase the resolution of a narrow-band optical system that is normally composed of a prism and a grating, or to use a long pulse of a laser pulse as described in Patent Document 1. There is a method by conversion. However, an increase in the resolution of a narrow-band optical system or an ultra-narrow band due to a long pulse generally leads to a decrease in pulse energy, such as an increase in optical loss. In other words, the band narrowing and the pulse energy are in a trade-off relationship.
Regarding the repetition frequency increase, a repetition frequency exceeding 4 kHz is technically difficult from the viewpoint of CoO (Cost of operation). Therefore, there is a natural limit to increase the output by increasing the repetition frequency while maintaining a very narrow band in one laser.

Therefore, in order to eliminate the trade-off between ultra-narrow band and pulse energy and satisfy both requirements simultaneously, an ultra-narrow band oscillator laser (oscillation stage laser) and an amplifier laser (amplification stage laser) that amplifies the output For example, Patent Document 2, Patent Document 3, and the like have proposed a two-stage laser apparatus that uses the two in synchronization.
The first oscillation stage laser has a very narrow band spectrum with low pulse energy. In the second amplification stage laser, only the pulse energy is amplified while maintaining the ultra narrow band spectrum of the oscillation stage laser. Since this method does not include an optical loss such as LNM (narrow band optical system) in the second amplification stage laser, the laser oscillation efficiency is very high. This synchronous laser device makes it possible to obtain a desired ultra-narrow band spectrum and laser output.
The two-stage laser apparatus is roughly classified into a MOPA system in which no resonator mirror is provided on the amplifier side and a MOPO system in which a resonator mirror is provided.

Configuration examples of the two-stage laser apparatus are shown in FIGS.
FIG. 10 shows a configuration example of a conventional two-stage laser apparatus of the MOPA system, and FIG. 11 shows a configuration example of an amplification stage laser in the MOPO system. As the oscillation stage laser of FIG. 11, for example, the same one as the oscillation stage laser shown in FIG. 10 is used. 10 and 11 are schematic views of the laser device as viewed from above.
In FIG. 10, the laser beam emitted from the oscillation stage laser 1 has a function as a seed laser beam (seed laser beam) of the laser device. The amplification stage laser 2 has a function of amplifying the seed laser beam. That is, the overall spectral characteristics of the laser device are determined by the spectral characteristics of the oscillation stage laser 1. Then, the laser output (energy or power) from the laser device is determined by the amplification stage laser 2.
The laser chambers 1a and 2a have a discharge part inside. The discharge part is composed of a pair of cathodes, an anode electrode 1b, a cathode, and an anode electrode 2b that are installed vertically on the paper surface. When a high voltage pulse is applied to the pair of electrodes from the power sources 1c and 2c, a discharge is generated between the electrodes. 10 and 11, only the upper electrode is shown. Window members 1d and 2d made of a material that is transparent to laser oscillation light such as CaF ₂ are installed at both ends of the optical axis extension of the pair of electrodes 1b and 2b installed in the chambers 1a and 2a, respectively. Has been. Here, the surfaces (outer surfaces) opposite to the chambers 1a and 2a of both window members are arranged in parallel to each other and at a Brewster angle in order to reduce reflection loss with respect to the laser beam.
The oscillation stage laser 1 has a narrowband module (narrowband optical system) 3 constituted by a magnifying prism 3b and a grating (diffraction grating) 3a, an optical element in the narrowband module 3 and a front mirror 1f. The laser resonator is configured with
A laser beam (seed laser beam) from the oscillation stage laser 1 is guided and injected into the amplification stage laser 2 by a beam propagation system including a reflection mirror (not shown).

In the MOPO system shown in FIG. 11, an unstable resonator having a magnification of, for example, 3 times or more is employed for the amplification stage laser 2 so that it can be amplified even with a small input.
In the case shown in FIG. 11, the rear side mirror 2e of the unstable resonator of the amplification stage laser 2 has a hole, and the laser that has passed through this hole is reflected and injected as indicated by the arrow in the above figure. The seed laser beam expands and effectively passes through the discharge part, increasing the power of the laser beam.
Then, a laser is emitted from a front mirror 2f composed of a convex mirror.

The synchronous controller 10 shown in FIGS. 10 and 11 generates an OSC trigger signal and an AMP trigger signal to be supplied to the power sources 1c and 2c based on a trigger signal given from the exposure apparatus 27 via the interface 28, and the power source is generated by this trigger signal. A high voltage pulse signal is generated from 1c and 2c, and discharge to the oscillation stage laser 1 and the amplification stage laser 2 is started. At that time, the synchronous controller 10 controls the delay time of the trigger signal applied to the power supplies 1c and 2c, and controls the discharge timing of the oscillation stage laser 1 and the amplification stage laser 2.
That is, first, an OSC trigger signal is transmitted to the power supply 1c of the oscillation stage laser 1 as an ON command for applying a high voltage pulse to the pair of electrodes 1b of the oscillation stage laser 1 from the power supply 1c. Then, after a predetermined time, an AMP trigger signal as an ON command is transmitted to the power source 2c of the amplification stage laser 2.
The predetermined time is a time for synchronizing the timing at which the seed laser beam enters the amplification stage laser 2 from the oscillation stage laser 1 and the timing at which the amplification stage laser 2 discharges. As will be described later, when the discharge circuit for generating discharge in the laser chamber and exciting the laser gas includes a magnetic pulse compression circuit comprising a capacitor and a saturable reactor, the charging voltage (V) of the capacitor There is a relationship that the value of the Vt product, which is the product of the charge transfer time (t), is constant.
Therefore, depending on the value of the voltage applied to each of the pair of electrodes 1b of the oscillation stage laser 1 and the pair of electrodes 2b of the amplification stage laser 2, the synchronous controller 10 first sends the power supply 2c of the amplification stage laser 2 as an ON command. A trigger signal may be transmitted to the power source 1c of the oscillation stage laser 1 after a predetermined time after transmitting the trigger signal.

FIG. 12 shows an example of a discharge circuit for generating a discharge in the laser chamber and exciting the laser gas in the two-stage laser apparatus described above. The discharge circuit shown in FIG. 12 is applied to each of the oscillation stage laser and the amplification stage laser.
The discharge circuit of FIG. 12 is a two-stage magnetic pulse compression circuit (hereinafter also referred to as an MPC circuit) using a charger Ch for charging a main capacitor C0 and three magnetic switches SR1, SR2, SR3 comprising a saturable reactor. Consists of.
The magnetic switch SR1 is for reducing switching loss in the solid-state switch SW which is a semiconductor switching element such as IGBT, and is also called magnetic assist. A two-stage magnetic pulse compression circuit is constituted by a capacitance transfer type circuit composed of the capacitor C1 and the first magnetic switch SR2 and a capacitance transfer type circuit composed of the capacitor C2 and the second magnetic switch SR3.
The energy charged in the main capacitor C0 by the charger Ch is subjected to a pulse compression operation such that the pulse width of the current pulse flowing through each stage is sequentially reduced as the magnetic pulse compression circuit is transferred, and the peaking capacitor Cp is charged. A strong discharge with a short pulse is realized between the main discharge electrodes E and E.
JP 2001-156367 A JP 2001-024265 A JP 2002-198604 A

In the two-stage laser apparatus, it is necessary to adjust the timing at which the laser beam emitted from the oscillation stage laser is injected into the amplification stage laser and the timing at which the amplification stage laser is discharged. That is, as described above, it is necessary to provide a predetermined delay time for the discharge of the oscillation stage laser, the emission timing, the discharge of the amplification stage laser, and the emission timing. If the timings of discharge and light emission of both are shifted, the laser beam emitted from the oscillation stage laser is not amplified well.
The synchronous controller 10 transmits the above delay time between the timing at which the trigger signal as the ON command is transmitted to the power source 1c of the oscillation stage laser 1 and the timing at which the trigger signal as the ON command is transmitted to the power source 2c of the amplification stage laser 2. The predetermined time) is set.
Here, if the frequency of the trigger input given to the power supplies 1c and 2c exceeds the maximum frequency limit value, the power supplies 1c and 2c may be damaged or deteriorated.
Therefore, conventionally, the maximum allowable frequency is limited to the trigger input given from the exposure apparatus 27 via the interface 28.
However, as described above, the synchronous controller 10 delays and outputs the trigger given from the interface 28. If the delay time is different for each control cycle, the frequency of the trigger given from the interface 28 is allowed. Even within the frequency limit value, the frequency of the OSC trigger signal and the AMP trigger signal input to the power supplies 1c and 2c exceeds the allowable frequency value (the time interval between the OSC trigger signal and the AMP trigger signal is a predetermined time or less). Cases arise.
The present invention has been made in view of the above circumstances, and prevents the frequency of the trigger signal output from the synchronous controller from exceeding the allowable maximum frequency limit, thereby preventing the power supplies 1c and 2c from being damaged or deteriorated, thereby providing failure reliability. The purpose is to improve the performance.

In the present invention, the above problem is solved as follows.
(1) A first capacitor that is charged to a high voltage, a first switch, and a pulse that compresses and outputs the charge stored in the first capacitor when the first switch is turned on. A first magnetic pulse compression circuit, a first laser chamber in which a laser gas is sealed, and a first pair disposed in the first laser chamber and connected to an output end of the first magnetic pulse compression circuit. Stored in the second capacitor when the second switch is turned on, the first gas laser device including the first discharge electrode, the second capacitor charged to a high voltage, the second switch, and the second switch. A second magnetic pulse compression circuit that pulse-compresses and outputs the generated electric charge, a second laser chamber in which a laser gas is sealed, and the second magnetic pulse compression circuit disposed in the second laser chamber. Out A second gas laser device including a second pair of discharge electrodes connected to the ends, injecting a laser beam emitted from the first gas laser device, and amplifying and emitting the injected laser beam; In order to adjust the light emission timing of at least one charger for charging the first capacitor and the second capacitor, and the first gas laser device and the second gas laser device, the first switch and the second capacitor In the two-stage laser apparatus including a synchronous controller for controlling the operation timing of the two switches, the synchronous controller is provided with a trigger delay setting means, a trigger interval determining means, and a means for stopping the output of the trigger signal.
Then, when the operation timing signals of the first and second switches are given from the outside by the trigger delay setting means , the discharge is started after the voltage is applied to the first discharge electrode and the second discharge electrode. The first and second switch operation timing signals given from the outside are calculated from the time until the first and second magnetic pulse compression circuits and the transition time of the pulse compression operation in the first magnetic pulse compression circuit and the second magnetic pulse compression circuit . The delay times of the trigger signals of the first switch and the second switch are calculated, respectively, and delayed by the calculated delay time from the operation timing signals of the first and second switches, so that the first switch and the second switch are delayed. 2 trigger signal is output.
At that time, the trigger interval determining means obtains the time interval of the delayed trigger signal of the first switch and the time interval of the delayed trigger signal of the second switch, and The time interval of the trigger signal and the time interval of the trigger signal of the second switch are compared with a preset threshold value, respectively, and the time interval of the trigger signal of the first switch or the time interval of the trigger signal of the second switch but it is smaller than the allowable maximum frequency limit preset the threshold so as not to exceed the trigger signal stops the output of the first and trigger signal of the second switch.
(2) The trigger interval determination means includes a means for measuring an interval of the operation timing signal of the first switch given from the outside and a time interval of the operation timing signal of the second switch; The sum of the difference between the delay time of the trigger signal of the first switch and the delay time of the trigger signal of the first switch calculated this time and the threshold value is the time of the operation timing signal of the first switch. Means for determining whether the time interval of the trigger signal of the first switch is smaller than a preset threshold by comparing with the interval, and the delay time of the trigger signal of the second switch calculated last time, The difference between the calculated delay time of the trigger signal of the second switch and the threshold value is compared with the time interval of the operation timing signal of the second switch. And the time interval of the trigger signal of the second switch is composed of a means for determining whether smaller than a preset threshold.

Further, the two-stage laser apparatus can be configured as follows.
(A) The second stage laser device further includes a first light emission or discharge monitor for measuring light emission or discharge timing of the first gas laser device, and a second light emission or discharge timing for measuring the second gas laser device. A light emission or discharge monitor is provided, and the synchronous controller feedback corrects the operation timing of the first switch and the second switch based on the first light emission or discharge monitor and the second light emission or discharge monitor.
(B) Correction in consideration of the discharge start timing in the first discharge electrode and the second discharge electrode is performed by correcting the charge voltage values of the first capacitor and the second capacitor, the first laser chamber, and the second This is performed based on the laser gas pressure value in the laser chamber.
(C) Correction in consideration of the operation of the first magnetic pulse compression circuit and the second magnetic pulse compression circuit is performed by correcting the charging voltage values of the first capacitor and the second capacitor and the first magnetic pulse compression circuit. And based on the temperature value of the circuit element which comprises the 2nd magnetic pulse compression circuit.
(D) In the above, the first magnetic pulse compression circuit and the second magnetic pulse compression circuit having different circuit constants are used.
(E) The first electrode configuration and the second electrode configuration are different from each other.
(F) One charger is used to charge the first and second capacitors.

  In the present invention, when the time interval of the trigger signal of the first switch or the time interval of the trigger signal of the second switch is smaller than a preset threshold by the trigger interval determining means, the first and second Since the trigger signal output of the switch is stopped, the frequency of the trigger input given to the power supply of the oscillation stage laser and the power supply of the amplification stage laser can be prevented from exceeding the maximum frequency limit value. It is possible to prevent the power source from being damaged or deteriorated.

As shown in FIGS. 10 and 11, the two-stage laser apparatus is roughly classified into a MOPA system in which no resonator mirror is provided on the amplification side and a MOPO system in which a resonator mirror is provided. In the following embodiments of the present invention, a two-stage laser apparatus using the MOPO method will be described. In the case of the MOPA system, as shown in FIG. 10, the amplification stage laser (AMP) has a configuration in which no resonator mirror is attached.
FIG. 1 is a diagram showing a configuration example of a two-stage laser apparatus as a premise of the present invention, and is an outline when the apparatus is viewed from the side. Although FIG. 1 shows a configuration example in which there are two chargers for charging the main capacitor of the discharge circuit of the laser device, the main capacitor may be charged by a single charger.
In FIG. 1, a laser beam emitted from an oscillation stage laser (OSC) 1 has a function as a seed laser beam (seed laser beam) of a two-stage laser apparatus. The amplification stage laser (AMP) 2 has a function of amplifying the seed laser beam. That is, the overall spectral characteristics of the laser device are determined by the spectral characteristics of the oscillation stage laser 1. Then, the laser output (energy or power) from the laser device is determined by the amplification stage laser 2.

In the oscillation stage laser 1 and the amplification stage laser 1, the laser chambers 1a and 2a each having the laser chambers 1a and 2a are filled with the laser gas supplied from the laser gas supply unit, the insides are opposed to each other, and a predetermined distance is provided. A pair of electrodes 1b and 2b separated from each other are provided.
When the two-stage laser device is a fluorine molecule (F ₂ ) laser device, both the oscillation stage laser 1 and the amplification stage laser 2 have fluorine (F ₂ ) gas, helium (He) and neon (Ne) in the chambers 1a and 2a. A laser gas comprising a buffer gas comprising, for example, is filled. When the two-stage laser device is a KrF laser device, both the oscillation stage laser 1 and the amplification stage laser 2 have krypton (Kr) gas, fluorine (F ₂ ) gas, helium (He) or neon (Ne) in the chambers 1a and 2a. ) Etc. are filled with a laser gas.
Further, when the two-stage laser apparatus is an ArF laser apparatus, both the oscillation stage laser 1 and the amplification stage laser 2 are provided with argon (Ar) gas, fluorine (F ₂ ) gas, helium (He) or neon in the chambers 1a and 2a. A laser gas composed of a buffer gas composed of (Ne) or the like is filled.

Both the oscillation stage laser 1 and the amplification stage laser 2 have a discharge portion inside the laser chambers 1a and 2a. The discharge part is composed of a pair of cathodes and anode electrodes 1b and 2b installed vertically in the direction parallel to the paper surface. When a high voltage pulse is applied to the pair of electrodes 1b and 2b from the power sources 1c and 2c, a discharge is generated between the electrodes 1b and 2b.
Further, both the oscillation stage laser 1 and the amplification stage laser 2 transmit the laser oscillation light such as CaF ₂ at the upper ends of the pair of electrodes 1b and 2b installed in the chambers 1a and 2a as described above. A window member (not shown) made of a flexible material is installed. Here, the surfaces of the window members opposite to the chamber are parallel to each other and installed at a Brewster angle in order to reduce reflection loss with respect to the laser beam. Moreover, the window is installed so that the P-polarized component of the laser beam is vertical.
A cross flow fan (not shown) is installed in the chambers 1a and 2a, and the laser gas is circulated in the chambers 1a and 2a to send the laser gas to the discharge part. In the chambers 1a and 2a, heat exchangers 1g and 2g for adjusting the temperature of the laser gas are provided.
The oscillation stage laser 1, the amplification stage laser 2 together, F ₂ gas to the chamber, for supplying a buffer gas F ₂ gas supply system, the buffer gas supply system, and a gas exhaust system is provided for exhausting the laser gas in the chamber ing. 1 and 2, these are collectively shown as “gas supply / exhaust control valve 16a” and “gas supply / exhaust control valve 16b”.
In the case of a KrF laser device and an ArF laser device, a Kr gas supply system and an Ar gas supply system are also provided. The gas pressure in the chamber is monitored by pressure sensors P1 and P2, and the gas pressure information is sent to the utility controller 24. The utility controller 24 controls the gas supply / distribution control valves 16a and 16b to control the gas composition and gas pressure in the oscillation stage chamber 1a and the amplification stage chamber 2a, respectively.

The oscillation stage laser 1 has a band narrowing module 3 constituted by a magnifying prism and a grating (diffraction grating), and a laser resonator is constituted by an optical element in the band narrowing module 3 and a front mirror (OC) 1f. To do. Alternatively, although not shown, a band narrowing module using an etalon and a total reflection mirror may be used instead of the magnifying prism and the grating. Part of the laser light emitted from the oscillation stage laser 1 and the amplification stage laser 2 is branched by a beam splitter (not shown) and guided to the monitor modules 15a and 15b. The monitor modules 15a and 15b monitor laser beam characteristics such as the output, line width, and center wavelength of the oscillation stage laser 1 and the amplification stage laser 2, respectively.
In FIG. 1, monitor modules are installed in both the oscillation stage and the amplification stage laser, but only one of them may be installed.
The center wavelength signal from the monitor modules 15 a and 15 b is sent to the wavelength controller 23. Then, the wavelength controller 23 drives the optical element in the narrowband module 3 by the driver 18, selects the wavelength, and controls the wavelength so that the center wavelength of the oscillation stage laser 1 becomes a desired wavelength.
The wavelength control described above is performed based on the wavelength information from the monitor module 15b through which a part of the laser light emitted from the amplification stage laser 2 is guided, so that the wavelength of the laser light emitted from the oscillation stage laser 1 is predetermined. It is also possible to issue a command from the wavelength controller to the driver 18 so that the wavelength becomes the same wavelength.
Laser output signals from the monitor modules 15 a and 15 b are sent to the energy controller 22. Then, the applied voltage is controlled via the synchronous controller 21, and the energy of the oscillation stage laser 1 and the amplification stage laser 2 is controlled to a desired value.

The laser beam (seed laser beam) from the oscillation stage laser 1 passes through the monitor module 15a, and is then guided to the amplification stage laser 2 by a beam propagation system 17 including a reflection mirror and the like provided for adjusting the optical axis. Injected.
In the MOPO method, an unstable resonator composed of, for example, an amplification stage output mirror 2f and an amplification stage rear-side mirror 2e with a magnification of 3 times or more is employed for the amplification stage laser 2 so that it can be amplified even with a small input. The
The rear side mirror 2e of the unstable resonator of the amplification stage laser in the MOPO system has a hole, and the laser that has passed through this hole is reflected as indicated by the arrow in the above figure, and the injected seed laser beam is enlarged. As a result, the laser beam effectively passes through the discharge part and the power of the laser beam increases. The laser is emitted from the amplification stage output mirror 2f.
The concave mirror 2e is provided with a spatial hole in the center and an HR (High Reflection) coat on the periphery. An HR coat is applied to the center of the convex mirror 2f, and an AR (Anti Reflection) coat is applied to the surrounding laser emission part.
The holes of the convex mirror 2f are not spatially opened, and a mirror substrate with an AR coating applied only to the holes may be used. Moreover, you may use the unstable resonator which does not give a transmission part to a mirror.

The pair of electrodes 1b and 2b of the oscillation stage laser 1 and the amplification stage laser 2 are respectively provided with a power source 1c constituted by a switch 12a-magnetic pulse compression circuit (MPC) 13a and a switch 12b-magnetic pulse compression circuit (MPC). A power source 2c configured by 13b is connected.
Then, a high voltage pulse is applied from the power supplies 1c and 2c, and discharge occurs between the electrodes 1b and 2b. By this discharge, the laser gas filled in the laser chambers 1a and 2a is excited. The power supplies 1c and 2c are charged by the charger 11.
Further, the temperature in the magnetic pulse compression circuits 13 a and 13 b is monitored by the temperature sensors T 1 and T 2, and the signal is sent to the synchronous controller 21.
In power supplies 1c and 2c, a capacitor (main capacitor C0 in the discharge circuit shown in FIG. 17) is charged by charger 11 (or chargers 11a and 11b). When the switches 12a and 12b are turned on, the energy charged in the capacitors is transferred to the magnetic pulse compression circuits 13a and 13b as voltage pulses, pulse-compressed, and applied to the pair of electrodes 1b and 2b.

The switches 12a and 12b are turned on and off by an operation command (trigger signal) from the synchronous controller 21.
The synchronous controller 21 is configured by a switch 12a-magnetic pulse compression circuit 13a so that a discharge occurs in the amplification stage laser 2 at a timing when the laser beam emitted from the oscillation stage laser 1 is injected into the amplification stage laser 2. A trigger signal is sent to the power source 2c constituted by the power source 1c and the switch 12b-magnetic pulse compression circuit 13b.
If the discharge timing of the oscillation stage laser 1 and the amplification stage laser 2 is shifted, the laser beam emitted from the oscillation stage laser 2 is not efficiently amplified. The synchronous controller 21 is a power supply 1c for the oscillation stage laser 1 based on the discharge start information of the oscillation stage laser 1 and the amplification stage laser 2 from the light / discharge detectors 14a and 14b and the laser output information from the energy controller 22. A delay time is set between the OSC trigger signal sent to the power supply 2 and the AMP trigger signal sent to the power source 2c of the amplification stage laser 2.
The utility controller 24, the energy controller 22 and the wavelength controller 23 are connected to the main controller 26. The main controller 26 is connected to an exposure device 28 via an interface 27.
The main controller 26 distributes the control share to each controller in accordance with a command from the exposure apparatus 28, and each controller performs control shared by the command.

As will be described later, counting starts when the synchronous controller 21 sends a trigger signal, and the light / discharge detectors 14a and 14b emit laser light, light emission during discharge (hereinafter collectively referred to as light emission) or discharge. Is provided with a light emission measurement counter 25a (hereinafter referred to as a CO counter) and a light emission measurement counter 25b (hereinafter referred to as a CA counter) that stop counting when the start of the signal is detected, and based on the count values of the counters 25a and 25b, As described later, the timing for triggering the oscillation stage laser 1 and the amplification stage laser 2 is determined.
The light / discharge detectors 14a and 14b described above are sensors that detect at least one of laser light emission, light emission during discharge, discharge current, discharge voltage, and electromagnetic waves generated by discharge. Here, different ones of the oscillation stage laser 1 and the amplification stage laser 2 may be detected. For example, the start of laser emission may be detected by the oscillation stage laser 1 and the start of discharge may be detected by the amplification stage laser 2.
1 shows the case where the laser resonator of the amplification stage laser 2 of the MOPO system is an unstable resonator, it may be a stable resonator.
In the MOPA method, the number of times that the light passes through the amplification stage laser is one, but is not limited to this. For example, a folding mirror may be provided to pass the amplification stage laser a plurality of times. With this configuration, it becomes possible to extract laser light with higher output.

Next, synchronous control of the oscillation stage laser 1 and the amplification stage laser 2 in the two-stage laser apparatus of the embodiment of the present invention will be described.
(1) Control in Energy Controller FIG. 2 shows a process flow in the energy controller 22, and the process in the energy controller 22 will be described with reference to FIG.
(i) The pulse energy of the laser light emitted from the oscillation stage laser 1 and the amplification stage laser 2 is detected by the monitor modules 15a and 15b. The monitor modules 15a and 15b send detection value signals to the energy controller 22 (step S101 in FIG. 2).
(ii) The pulse energies E1 and E2 are obtained from the detection value signals received from the monitor modules 15a and 15b. Then, the deviation ΔE1 between the target energies Et1 and E1 and the deviation ΔE2 between the target energies Et2 and E2 stored in advance or given from the main controller 26 are expressed as ΔE1 = E1−Et1 and ΔE2 = E2. -Et2 is calculated (step S102).
(iii) Next, based on the obtained deviations ΔE1 and ΔE2, charging voltage deviations ΔV1 and ΔV2 when charging the capacitors of the power supply 1c and the power supply 2c corresponding to obtaining the deviations ΔE1 and ΔE2 are obtained.
ΔV1 is obtained from the equation: ΔV1 = K · ΔE1, where K is a coefficient. ΔV2 is obtained from the equation: ΔV2 = K · ΔE2, where K is a coefficient (step S103).
(iv) The charging voltage HV1 for obtaining the target energy Et1 is obtained. That is, the correction is performed by adding ΔV1 obtained in step S103 to the previous charging voltage HV1 (when the discharge pulse before the current discharge pulse is generated) by the following equation.
HV1 (current) = HV1 (previous) + ΔV1
Further, a charging voltage HV2 for obtaining the target energy Et2 is obtained. That is, the correction is performed by adding ΔV2 obtained in step S203 to the previous charging voltage HV2 (when the discharge pulse before the current discharge pulse is generated) by the following equation (step S104).
HV2 (current) = HV2 (previous) + ΔV2
(v) the charging voltage value HV1, HV2 determined is larger than the laser gas injection voltage V _max 1, V _max 2, larger, injecting the laser gas (step S105). If it is smaller, go to step S106.
(vi) The charging voltage value (high voltage value) HV1 (current) data and the charging voltage value (high voltage value) HV2 (current) data obtained in step S104 are sent to the synchronous controller 21 and the main controller 26. (Step S106).

(2) Control in the synchronous controller The magnetic pulse compression circuit (MPC circuit) constituting the power supplies 1c and 2c is formed by connecting several stages of capacitance transfer type circuits composed of a saturable reactor and a capacitor as shown in FIG. is there.
By setting the inductance of the capacity transfer type circuit of each stage to be smaller as it goes to the subsequent stage, a pulse compression operation is performed so that the pulse width of the current pulse flowing through each stage is sequentially narrowed. Here, the transition time of each stage is inversely proportional to the voltage V applied to the saturable reactor, as shown in the following equation.
V · tm = (Constant)
That is, when the applied voltage V is high, the transition time tm decreases, and when the voltage V is low, the transition time tm increases.
Further, since the supersaturated reactor and the capacitor constituting the MPC circuit each have temperature characteristics, the transition time tm changes due to the change in the MPC internal temperature. The internal temperature varies depending on the oscillation frequency, oscillation time, burst operation duty, charging voltage, and the like.
The synchronous controller 21 uses, for example, an approximate expression based on the voltage V applied to the saturable reactor (the charge voltage values HV1, HV1) and the temperatures Tp1, Tp2 of the MPC circuit monitored by the temperature sensors T1, T2. The transition time tm is obtained by referring to a table in which the transition time tm with respect to the applied voltage and temperature is recorded.

On the other hand, the time (discharge start time) tb from when voltage is applied between the electrodes 1b and 2b of the chambers 1a and 2a to when discharge starts (discharge start time) tb is shown in FIG. The rise of the voltage becomes shorter because it increases (tb1), and the lower the charge voltage, the longer the voltage rise becomes (tb3).
Further, as shown in FIG. 3B, when the gas pressure in the chamber is high, the discharge start voltage becomes high (−V1), and thus the time until the start of discharge becomes long (tb3). On the contrary, when the gas pressure is low, the discharge start voltage is low (−V3) when the gas pressure is low, and therefore the time until the start of discharge is short (tb1). Therefore, the discharge start time tb is a function of the charging voltage and the gas pressure.
The synchronous controller 21 obtains the discharge start time tb based on the charging voltage HV and the gas pressure monitored by the pressure sensors P1 and P2.
In the present invention, the discharge start time is determined by changing the charge voltage and gas pressure in the range of use, measuring the discharge start time tb under each condition, creating a table recording these values, and synchronizing this table. Although a method (table method) input in advance to the controller 21 is used, calculation using an approximate expression is also possible.

Hereinafter, the synchronization control in the synchronization controller 21 will be described.
The outline of the synchronization control in the synchronization controller 21 is as follows.
(i) The transition time tm and the discharge start time tb are obtained from the charging voltages HV1 and HV2, the temperatures Tp1 and Tp2 of the MPCs 13a and 13b of the power supplies 1c and 2c, and the chamber pressures Pp1 and Pp2. From this tm, tb, the delay time (referred to as OSC-correction delay) from when the switch 12a of the power source 1c in the oscillation stage laser 1 is turned on until the discharge starts, the power of the power source 2c in the amplification stage laser 2 A delay time (AMP−correction delay) from when the switch 12b is turned on to when discharge starts is obtained.
(ii) Timing of triggering the power supplies 1c and 2c of the oscillation stage laser 1 and the amplification stage laser 2 based on the trigger signal sent from the exposure apparatus, the OSC-correction delay, and the AMP-correction delay during the first discharge And switches 12a and 12b are turned on.
(iii) The CO counter 25a and the CA counter 25b count the time from the pre-trigger signal (output after the charge signal stabilization period from the trigger signal) until the oscillation stage laser 1 and the amplification stage laser 2 start to emit or discharge. Then, the time from the output of the pre-trigger signal to the actual start of light emission or discharge is obtained.
(iv) During the second and subsequent discharges, based on the actual time counted by the CO counter 25a and CA counter 25b, OSC-correction delay obtained from the charging voltages HV1, HV2, temperatures Tp1, Tp2, and pressures Pp1, Pp2, The AMP-correction delay is corrected, the timing for triggering the power supplies 1c and 2c of the oscillation stage laser 1 and the amplification stage laser 2 is determined based on the corrected time, and the switches 2a and 2b are turned on.

Next, the configuration of the synchronous controller 21 will be described in detail.
FIG. 4 shows input / output signals of the synchronous controller 21.
As shown in the figure, a charger 11a for the oscillation stage laser 1 and a charger 11b for the amplification stage laser 2 are provided, and the synchronous controller 21 sends charge control signals HV1 and HV2 to the charger 11a and the charger 11b. Output.
The synchronous controller 21 includes a trigger signal supplied from the interface 27, charging voltages HV1 and HV2 supplied from the energy controller 22, pressures Pp1 and Pp2 in the chambers 1a and 2a of the oscillation stage laser 1 and the amplification stage laser 2, and light / discharge detection. The light / discharge detection signals output from the devices 14a and 14b and the temperatures Tp1 and Tp2 monitored by the temperature sensors T1 and T2 are input. Based on these signals, the synchronous controller 21 outputs the charging signals HV1 and HV2 to the charger 11, determines the timing for triggering the switches of the power supplies 1c and 2c, and outputs the OSC trigger signal and the AMP trigger signal.

FIG. 5 is a diagram showing a configuration of the synchronous controller 21 according to the embodiment of the present invention.
As shown in the figure, the synchronous controller 21 includes a CPU 21a, an FPGA 21b, a first clock generator 21c, and a second clock generator 21d.
In this embodiment, the CO counter 25a and the CA counter 25b are provided in the synchronous controller 21, and the time from when the pre-trigger signal is output until when the light emission or discharge actually starts is counted.
The CPU 21a uses the temperatures Tp1 and Tp2 of the MPCs 13a and 13b and the pressure data of the OSC chamber 1a and the AMP chamber 2a, as will be described later, an OSC trigger delay setting value for adjusting the timing for triggering the power source 1c, An AMP trigger delay setting value for adjusting the timing of triggering 2c is output to the FPGA 21b.
The FPGA 21b includes a chargeout / trigger signal generation unit 211, an OSC trigger delay unit 212 for adjusting the timing for triggering the power source 1c, an AMP trigger delay unit 213 for adjusting the timing for triggering the power source 2c, and an OSC-counter. It comprises an enable creation unit 214, an OSC-counter reset creation unit 215, an AMP-counter enable creation unit 216, an AMP-counter reset creation unit 217, and a trigger interval determination unit 218.

When the chargeout / trigger signal generation unit 211 receives a trigger signal (triggin) from the interface 27, the chargeout / trigger signal generation unit 211 generates and outputs charge control signals (Chargout) HV1 and HV2 based on the trigger signal (triggin). A pre-trigger signal (Pre_Trig) is output. This pre-trigger signal (Pre_Trig) is given to the OSC trigger delay unit 212 and the AMP trigger delay unit 213.
In the OSC trigger delay unit 212 and the AMP trigger delay unit 213, the pre-trigger signal (Pre_Trig) is delayed by the OSC trigger delay setting value and the AMP trigger delay setting value given from the CPU 21a. The delayed trigger signal is supplied to the switch 12a of the power source 1c as an OSC trigger signal through the gate G1, and is also supplied to the switch 12b of the power source 2c as an AMP trigger signal through the gate G2.
The trigger interval determination unit 218 determines the interval between the OSC trigger signal and the AMP trigger signal, the frequency of the OSC trigger signal and the AMP trigger signal exceeds an allowable frequency value, and the time interval between the OSC trigger signal and the AMP trigger signal is a limit value. When the following occurs, the gates G1 and G2 are closed, and the supply of the OSC trigger signal and the AMP trigger signal to the power supplies 1c and 2c is stopped.

On the other hand, the pre-trigger signal (Pre_trig) output from the chargeout / trigger signal generator 211 is given to the OSC-counter reset generator 215 and the AMP-counter reset generator 217, and the OSC-counter reset generator 215, AMP- The counter reset creating unit 217 starts counting of the CO counter 25a and the CA counter 25b by the pre-trigger signal. The CO counter 25a and the CA counter 25b are cleared by the trigger signal (Trig).
When the oscillation stage laser 1 starts light emission or discharge by the OSC trigger, the light emission or discharge is detected by the light / discharge detector 14a, and the OSC-counter enable creation unit 215 detects the light emission or discharge based on the detection signal. The count of the CO counter 25a is stopped. When the amplification stage laser 2 starts to emit light or discharge by the AMP trigger, the light emission or discharge is detected by the light / discharge detector 14b, and the AMP-counter enable creating unit 216 uses the detection signal to The count of the CA counter 25b is stopped. The count values of the CO counter 25a and the CA counter 25b are values corresponding to the time from the output of the pre-trigger signal to the actual start of light emission or discharge.
The CO counter 25a and the CA counter 25b count the clock output from the second clock generator 21d that generates a high-speed clock, and then start emitting light or discharging after the trigger signal is output. Count time.
The signal levels of the output signals from the CO counter 25a and CA counter 25b are converted by a level conversion IC and transmitted to the CPU 21a via a buffer or the like. Based on the measurement results from the pre-trigger signal to the light emission or discharge time of the oscillation stage laser 1 and the amplification stage laser 2, the CPU 21a performs a feedback calculation of the delay time of each trigger as will be described later.

FIG. 6 is a diagram illustrating a configuration example of the trigger interval determination unit 218.
The trigger interval determination unit 218 includes a counter 225 and a register 226. The counter 225 counts the time interval of the trigger signal and causes the register 226 to hold the trigger signal.
That is, when a trigger signal is generated, this signal is differentiated and given to the counter 225, "0" is loaded into the counter 225, and the counter 225 starts counting the clock pulse clk. The above counting is performed until the next trigger signal is input, and the count value counted during that time is set in the register 226. As a result, the time interval Trig_int (this value is B) of the trigger signal given from the exposure device 28 is set in the register 226.
On the other hand, OSC_td (n) which is the sum of “OSC trigger delay setting value” in the nth control cycle and “time from when the trigger signal is input until the pre-trigger signal is output”, and (n−1) cycles OSC_td (n−1), which is the sum of the “OSC trigger delay setting value” of the eye and “the time from when the trigger signal is input to when the pre-trigger signal is output”, is obtained from the CPU 21a and is respectively buffered 221a, 221b. Then, the arithmetic unit 223 adds a preset trigger interval limit value Trig_min (for example, 10 μs) to the difference between OSC_td (n−1) and OSC_td (n) to obtain an addition result A.
That is, the calculator 223 performs the following calculation.
A = [OSC_td (n-1)]-[OSC_td (n)] + [Trig_min]
Similarly, AMP_td (n) which is the sum of “AMP trigger delay setting value” of the nth control cycle and “time from when the trigger signal is input until the pre-trigger signal is output”, (n−1) AMP_td (n−1), which is the sum of the “AMP trigger delay setting value” in the cycle and “the time from when the trigger signal is input until the pre-trigger signal is output”, is held in the buffers 222a and 222b, respectively. Then, the arithmetic unit 224 adds a preset trigger interval limit value Trig_min to the difference between AMP_td (n-1) and AMP_td (n) to obtain an addition result A '. That is, the calculator 224 performs the following calculation.
A '= [AMP_td (n-1)]-[AMP_td (n)] + [Trig_min]

The first comparator 227 compares the trigger signal time interval B held in the register 226 with the above A, and if A> B, the OSC trigger interval becomes shorter than the limit value and the error “1” "Is output.
The second comparator 228 compares the time interval B of the trigger signal held in the register 226 with the above A ′, and if A ′> B, it is assumed that the AMP trigger interval is shorter than the limit value. Error “1” is output.
The OR gate 229 outputs “0” when the output of at least one of the comparator 227 or the comparator 228 becomes “1”. As a result, the gates G1 and G2 are closed, and the output of the OSC trigger signal and the AMP trigger signal is stopped. When a trigger interval error occurs, the CPU 21a is interrupted to notify the error, and the main controller 26 (see FIG. 1) is notified of the occurrence of the error.

FIG. 7 is a diagram illustrating the determination process in the trigger interval determination unit 218.
As shown in FIG. 6A, when the time interval between the OSC trigger signal in the (n-1) control cycle and the OSC trigger signal in the n control cycle is Tn, Tn is expressed by the following equation.
Tn = Trig_int + OSC_td (n) −OSC_td (n−1)
This value Tn needs to be larger than the limit value Trig_min. If Tn becomes smaller than Trig_min, an error (the trigger signal frequency exceeds the allowable frequency) is caused and output of the trigger signal is stopped.
That is, an error occurs when the following expression (1) is satisfied.
Trig_int + OSC_td (n) -OSC_td (n-1) <Trig_min (1)
Similarly, as shown in FIG. 7B, when the time interval between the AMP trigger signal in the (n-1) control cycle and the AMP trigger signal in the n control cycle is Tn ′, Tn ′ is expressed by the following equation. expressed.
Tn ′ = Trig_int + AMP_td (n) −AMP_td (n−1)
This value Tn ′ needs to be larger than the limit value Trig_min. If Tn ′ becomes smaller than Trig_min, an error (the trigger signal frequency exceeds the allowable frequency) is caused and output of the trigger signal is stopped.

That is, an error occurs when the following expression (2) is satisfied.
Trig_int + AMP_td (n) −AMP_td (n−1) <Trig_min (2)
From the above equations (1) and (2), the following equations (3) and (4) are obtained.
Trig_int <Trig_min−OSC_td (n) + OSC_td (n−1) (3)
Trig_int <Trig_min−AMP_td (n) + AMP_td (n−1) (4)
The arithmetic unit 223 obtains the right side of the above expression (3) and compares this value with the Trig_int held in the register 226 by the comparator 227. Thereby, it can be determined whether the time interval of the OSC trigger signal is smaller than the limit value Trig_min.
Similarly, the arithmetic unit 224 obtains the right side of the above equation (4), and compares this value with Trig_int held in the register 226 by the comparator 228. Thereby, it can be determined whether the time interval of the AMP trigger signal is smaller than the limit value Trig_min.

FIG. 8 is a flowchart showing the processing of the synchronous controller 21, and FIG. 9 is a synchronous controller control timing chart. Hereinafter, the synchronous control of the synchronous controller 21 will be described with reference to FIGS.
(i) The data of the charging voltage values HV1 and HV2 sent from the energy controller 22 is received. In addition, data of MPC internal temperatures Tp1, Tp2 of the magnetic compression circuit is received. Further, data (DATA1in, DATA2in) of the chamber gas pressures Pp1, Pp2 sent from the chamber gas pressure sensors Pp1, Pp2 are received (step S301 in FIG. 8, 1 and 4 in the timing chart).
The synchronous controller 21 takes in DATA1in data and DATA2in data at the rising edge of the data take-in command signals STROBE1 and STROBE2 (2 and 5 in the timing chart) and holds them as DATA1reg and DATA2reg (3 and 6 in the timing chart in FIG. 9).

(ii) The synchronization controller 21 receives the MPC 13a of the oscillation stage laser 1 as described above based on the DATA1reg and DATA2reg (data of the charging voltages HV1, HV2, and temperatures Tp1, Tp2) received and held in step S301 in FIG. The transition times tm1 and tm2 of the current pulse of the MPC 13b of the amplification stage laser 2 are obtained.
Further, as described above, the discharge start times tb1 and tb2 are obtained from DATA1reg and DATA2reg (data of the charging voltages HV1 and HV2 and pressures Pp1 and Pp2). Further, correction delays t1_delay (n) and t2_delay (n) are obtained from the sum of tm and tb as follows (step S302 in FIG. 8, timing charts 7 and 8).
t1_delay (n) = tm1 + tb2
t2_delay (n) = tm2 + tb2

(iii) It is determined whether or not it is the first laser oscillation (referred to as the first pulse) after the start of operation. If it is the first pulse, the process goes from step S303 to step S304.
In step S304, the generation timing of the trigger signal to the switch 12a of the power source 1c of the oscillation stage laser 1 is obtained.
In the case of the first pulse, as described above, t1_delay (n) is set to the trigger delay time to_switch (n) as shown in the following formula, and after generating the pre-trigger signal from this trigger delay time, the oscillation stage laser The time until the switch 12a of one power source 1c is triggered is determined.
to_switch (n) = t1_delay (n)
Similarly, in step S305, the generation timing of the trigger signal to the switch 12b of the power source 2c of the amplification stage laser 2 is obtained.
That is, as described above, t2_delay (n) is set to the trigger delay time ta_switch (n) as shown in the following formula, and after the pre-trigger is generated from this trigger delay time, the power supply 1c of the oscillation stage laser 1 is The time until the switch 12a is triggered is determined.
ta_switch (n) = t2_delay (n)

(iv) A trigger is received from the exposure device 28 such as a stepper via the interface 27 (step S306 in FIG. 8, 12 in the timing chart).
(v) The synchronous controller 21 creates a charge control signal (Chargout) and a pre-trigger signal (Pre_Trig) based on the trigger (step S307 in FIG. 8).
As described above, the synchronization controller 21 creates and outputs the pre-trigger signal (Pre_Trig) after the charger charging stabilization time tst has elapsed (13 and 14 in the timing chart).
(vi) The CO counter 25a that measures the light emission or discharge time of the oscillation stage laser 1 and the CA counter 25b that measures the light emission or discharge time of the amplification stage laser 2 at the start of output of the pre-trigger signal (Pre_Trig) created in step S307 are operated. (Step S308 in FIG. 8, timing charts 18 and 20).

(vii) An OSC trigger signal (OSC_trigout) that delays the OSC-trigger delay setting value from the pretrigger signal (Pre_Trig) and turns on the switch 12a of the power supply 1c of the oscillation stage laser 1 is output (step S309, timing chart 15). ).
Also, an AMP trigger signal (AMP_trigout) that delays the AMP-trigger delay setting value from the pretrigger signal (Pre_Trig) and turns on the switch 12b of the power supply 2c of the amplification stage laser 2 is output (step S310, timing chart 16). . As a result, the oscillation stage laser 1 and the amplification stage laser 2 start discharging.
(viii) The light / discharge detector 14a detects the light emission or discharge start timing to of the oscillation stage laser 1, and stops the CO counter 25a (step S311, 17 and 18 in the timing chart).
The light / discharge detector 14b detects the light emission or discharge start timing ta of the amplification stage laser 2 and stops the CA counter 25b (step S312, 19 and 20 in the timing chart).

(ix) When the first discharge is completed as described above, the process returns to step S301, and the data signals DATA1 and DATA2 of the charging voltage values HV1 and HV2, the internal temperatures Tp1 and Tp2, and the gas pressures Pp1 and Pp2 are set as described above. Then, the transition times tm1 and tm2 of the current pulses of the MPC 13a of the oscillation stage laser 1 and the MPC 13b of the amplification stage laser 2 are obtained.
Further, as described above, the discharge start times tb1 and tb2 are obtained from the charging voltages HV1 and HV2 and the pressures Pp1 and Pp2, and the correction delays t1_delay (n) and t2_delay (n) are obtained from the sum of tm and tb (step S301, S302).
(x) Since it is not the first pulse, the process goes from step S303 to step S313, and the feedback calculation of the oscillation stage laser 1 is performed from the following equation based on the value of the CO counter 25a as described above.
Δto_delay (n) = t _ot −t _CO
Here, t _ot is the target delay time from the trigger until the oscillation stage laser 1 emits or discharges, and t _CO is the time measured by the CO counter 25a (step S313, 7 in the timing chart).
Further, as described above, based on the value of the CA counter 25b, the feedback calculation of the amplification stage laser 2 is performed by the following equation.
Δta_delay (n) = t _At −t _CA
Here, t _At is the target delay time from the trigger to the time when the amplification stage laser 2 emits or discharges, and t _CA is the time measured by the CA counter 25b (step S314, 8 in the timing chart).

(xi) In the oscillation stage laser 1, the trigger delay time to_switch (n) is obtained by the following formula based on t1_delay (n) and the result Δto_delay (n−1) of the light emission / discharge timing feedback calculation. From the delay time, the time from when the trigger is generated to when the switch 12a of the power source 1c of the oscillation stage laser 1 is triggered is determined (step S315).
to_switch (n) = t1_delay (n) + Δto_delay (n−1)
Similarly, in the amplification stage laser 2, a trigger delay time ta_switch (n) is obtained by the following formula based on t2_delay (n) and the result Δta_delay (n−1) of the light emission / discharge timing feedback calculation. From the delay time, the time from when the trigger is generated to when the switch 12a of the power source 1c of the oscillation stage laser 1 is triggered is determined (step S316).
ta_switch (n) = t2_delay (n) + Δta_delay (n−1)

(xii) Go to step S317 and perform OSC trigger interval error calculation. Also, an AMP trigger interval error calculation is performed.
That is, the trigger signal time interval is counted by the counter 225 of the trigger interval determination unit 218, and the trigger frequency is latched in the register 226 (9 and 10 in the timing chart). Then, as shown in the equations (3) and (4), Trig_min−OSC_td (n) + OSC_td (n−1) is calculated and compared with the time interval Trig_int of the counted trigger signal.
Similarly, Trig_min−AMP_td (n) + AMP_td (n−1) is calculated and compared with the time interval Trig_int of the trigger signal (step 318, 11 in the timing chart).
When Trig_int <Trig_min−OSC_td (n) + OSC_td (n−1) or Trig_int <Trig_min−AMP_td (n) + AMP_td (n−1), the OSC trigger signal and the AMP trigger signal are output as an OSC trigger interval error. Stop (step S319).

In step S306, the trigger signal (triggin) is received from the exposure device 28 such as a stepper via the interface 27 as described above.
Hereinafter, as described above, the charge output signal and the pre-trigger signal are generated, and the CO counter 25a and the CA counter 25b are operated.
Then, the above OSC trigger interval error calculation is performed. If the trigger interval error is not detected, an OSC trigger signal (OSC_trigout) for turning on the switch 12a of the power source 1c of the oscillation stage laser 1 is output.
Also, the above AMP trigger interval error calculation is performed. If it is not a trigger interval error, an AMP trigger signal (AMP_trigout) for turning on the switch 12b of the power source 2c of the amplification stage laser 2 is output.
Further, the light / discharge detector 14a detects the light emission or discharge start timing to of the oscillation stage laser 1, stops the CO counter 25a, and the light / discharge detector 14b sets the light emission or discharge start timing ta of the amplification stage laser 2. Then, the CA counter 25b is stopped (steps S306 to S312 in FIG. 8).

By operating as described above, the time from the trigger to the light emission or discharge timing to and the time from the light emission or discharge timing ta can be controlled to be constant.
Moreover, by correcting with the set values of HV1 and HV2 from the energy controller, measured values of Tp1 and Tp2 from the MPC temperature sensor, and measured values of Pp1 and Pp2 from the chamber gas pressure sensor, the oscillation stage laser emission or The discharge timing and amplification stage laser emission or discharge timing can be controlled to be kept constant.
For this reason, the oscillation stage laser and the amplification stage laser can be individually configured to obtain optimum laser outputs, and the adjustment accuracy of light emission or discharge timing of both lasers can be improved and synchronized with high accuracy.
Further, when the time interval of the OSC trigger signal and the time interval of the AMP trigger signal is equal to or less than the limit values, the output of the OSC trigger signal and the AMP trigger signal is stopped to prevent the power supplies 1c and 2c from being damaged or deteriorated. And the reliability of the apparatus can be improved.

In general, the time from when the trigger signal of the exposure apparatus is transmitted until the light emission or discharge of the laser apparatus is set to a predetermined constant value. Further, in order to amplify the oscillation stage laser efficiently while maintaining a desired beam quality, a delay time from when the oscillation stage laser emits or discharges to when the amplification stage laser emits or discharges has a predetermined value. It needs to be maintained at the value.
Therefore, the trigger signal is actually transmitted by adding a predetermined value to the OSC trigger delay time [to_switch (n)] and the AMP trigger delay time [ta_switch (n)] obtained as described above. The delay time from the time when the laser device emits or discharges to the time when the oscillation stage laser emits or discharges and the amplification stage laser emits light is adjusted.

It is a figure which shows the structural example of the 2 stage laser apparatus used as the premise of this invention. It is a figure which shows the processing flow in an energy controller. It is a figure which shows the discharge start time at the time of charge voltage change and gas pressure change. It is a figure which shows the input / output signal of a synchronous controller. It is a figure which shows the structure of the synchronous controller of the Example of this invention. It is a figure which shows the structure of the trigger space | interval determination part provided in the synchronous controller of 1st Example of this invention. It is a figure explaining a trigger space | interval determination process. It is a flowchart which shows the process of a synchronous controller. It is a control timing chart of a synchronous controller. It is a figure which shows the structural example of the conventional 2 stage laser apparatus of a MOPA system. It is a figure which shows the structural example of the amplification stage laser in a MOPO system. It is a figure which shows the example of the discharge circuit for exciting a laser gas.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oscillation stage laser 2 Amplification stage laser 1a, 2a Laser chamber 1b, 2b Electrode 1c, 2c Power supply 3 Narrow-band module 11 Charger 11a, 11b Charger 12a, 12b Switch 13a, 13b Magnetic pulse compression circuit (MPC circuit)
14a, 14b Light / discharge detector 15a, 15b Monitor module 16a, 16b Gas supply / exhaust control valve 17 Beam propagation system 18 Driver 21 Synchronous controller 22 Energy controller 23 Wavelength controller 24 Utility controller 25a Light emission measurement counter (CO counter)
25b Light emission measurement counter (CA counter)
26 Main controller 27 Interface 28 Exposure device P1, P2 Pressure sensor T1, T2 Temperature sensor 21a CPU
21b FPGA
21c First clock generator 21d Second clock generator 211 Chargeout / trigger signal generator 212 Osc trigger delay unit 213 Amp trigger delay unit 214 Osc-counter enable generator 215 Osc-counter reset generator 216 Amp- Counter enable creation unit 217 Amp-Counter reset creation unit 218 Trigger interval determination unit 221a-222b Buffer 223, 224 Arithmetic unit 225 Counter 226 Register 227, 228 Comparator 229 No-gate

Claims (2)

A first capacitor that is charged to a high voltage, a first switch, and a first magnet that compresses and outputs the charge stored in the first capacitor when the first switch is turned on. A pulse compression circuit;
A first laser chamber containing a laser gas; and a first pair of discharge electrodes disposed in the first laser chamber and connected to an output end of the first magnetic pulse compression circuit. Gas laser device of
A second capacitor that is charged to a high voltage, a second switch, and a second magnet that pulse-compresses and outputs the charge stored in the second capacitor when the second switch is turned on. A pulse compression circuit;
A second laser chamber in which a laser gas is sealed, and a second pair of discharge electrodes disposed in the second laser chamber and connected to an output end of the second magnetic pulse compression circuit, A second gas laser device in which a laser beam emitted from the first gas laser device is injected, and the injected laser beam is amplified and emitted;
At least one charger for charging the first capacitor and the second capacitor, and the first switch and the second switch for adjusting the light emission timing of the first gas laser device and the second gas laser device. A two-stage laser apparatus including a synchronous controller for controlling the operation timing of the switches of
In the synchronous controller, when the operation timing signals of the first and second switches are given from the outside , the voltage is applied to the first discharge electrode and the second discharge electrode until the discharge starts. The first switch with respect to the operation timing signal of the first and second switches given from the outside from the time and the transition time of the pulse compression operation in the first magnetic pulse compression circuit and the second magnetic pulse compression circuit And calculating the delay time of the trigger signal of the second switch,
Trigger delay setting means for outputting the trigger signals of the first switch and the second switch by delaying the calculated timing by the calculated delay time from the operation timing signals of the first and second switches;
A time interval of the delayed trigger signal of the first switch and a time interval of the delayed trigger signal of the second switch are obtained, and the time interval of the trigger signal of the first switch and the second switch The trigger signal time interval is compared with a preset threshold value, and the trigger signal time interval of the first switch or the trigger signal time of the second switch is the maximum allowable frequency limit of the trigger signal. a trigger interval determining means for determining or smaller to than the preset the threshold so as not to exceed,
Time intervals of the first time interval of the switch of the trigger signal or a second switch of the trigger signal, when the smaller than a preset threshold, stops the output of the first and trigger signal of the second switch A two-stage laser device. The trigger interval determining means measures the interval of the operation timing signal of the first switch given from the outside and the time interval of the operation timing signal of the second switch;
The sum of the difference between the delay time of the trigger signal of the first switch calculated last time and the delay time of the trigger signal of the first switch calculated this time and the threshold value is the operation of the first switch. Means for determining whether the time interval of the trigger signal of the first switch is smaller than a preset threshold value by comparing with the time interval of the timing signal;
The sum of the difference between the previously calculated delay time of the trigger signal of the second switch and the delay time of the trigger signal of the second switch calculated this time and the threshold value is the sum of the second switch 2. The means for determining whether the time interval of the trigger signal of the second switch is smaller than a preset threshold value by comparing with the time interval of the operation timing signal. 2 stage laser device.

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