Laser apparatus, EUV light generation system, and method of controlling laser apparatus

Patent metadata

Field	Value
Publication number	US-10224686-B2
Application number	US-201615356763-A
Country	US
Kind code	B2
Filing date	Nov 21, 2016
Priority date	Jul 1, 2014
Publication date	Mar 5, 2019
Grant date	Mar 5, 2019

Abstract

A laser apparatus may include: an optical amplifier configured to amplify a laser beam outputted from a master oscillator; an optical-amplifier power supply configured to supply an alternating current for optical amplification to the optical amplifier; and a laser controller. The optical-amplifier power supply may include: an alternating current generation circuit including an inverter circuit configured to change output amplitude in accordance with a duty cycle, the alternating current generation circuit being configured to generate the alternating current from an output of the inverter circuit; and a power supply control circuit configured to hold control information defining correspondence relations between command values from the laser controller and duty cycles of the inverter circuit, determine a duty cycle corresponding to a command value received from the laser controller based on the control information, and provide the determined duty cycle to the inverter circuit.

First claim

What is claimed is:

1. A laser apparatus configured to generate a pulse laser beam, the laser apparatus comprising:
a master oscillator configured to output a pulse laser beam;
an optical amplifier configured to amplify the laser beam outputted from the master oscillator;
an optical-amplifier power supply configured to supply an alternating current for optical amplification to the optical amplifier; and
a laser controller configured to control the master oscillator and the optical-amplifier power supply,
wherein the optical-amplifier power supply includes:
a power supply control circuit configured to output gate signals with a pulse width corresponding to command values received from the laser controller and,
an inverter circuit configured to change output amplitude in accordance with the pulse width of the gate signals output from the power supply control circuit, and

wherein the optical-amplifier power supply is configured to supply the alternating current with output amplitude corresponding to each command value received from the laser controller.

2. The laser apparatus according to claim 1 , wherein the power supply control circuit is configured to hold control information defining correspondence relations between command values from the laser controller and pulse width of gate signals.

3. The laser apparatus according to claim 2 , wherein the laser controller is configured to acquire a measured value of output energy of the optical amplifier, calculate a difference between the measured value of the output energy and a target value of the output energy, and correct the control information based on the difference.

4. The laser apparatus according to claim 1 , further comprising a current monitor configured to monitor the alternating current,
wherein the laser controller is configured to compare the command value and an output value of the current monitor to determine a deterioration level of laser gas.

5. The laser apparatus according to claim 1 , wherein an interface between the laser controller and the power supply control circuit is configured with parallel I/O.

6. An EUV light generation system configured to irradiate a target with a pulse laser beam to generate EUV light, the EUV light generation system comprising:
a chamber;
a target supply device configured to supply a target into the chamber; and
a laser apparatus configured to output a pulse laser beam with which the target supplied into the chamber is to be irradiated,
wherein K is an integer equal to or greater than two,
wherein the laser apparatus includes:
a master oscillator configured to output a pulse laser beam;
K stages of optical amplifiers configured to amplify a pulse laser beam outputted from the master oscillator;
K optical-amplifier power supplies configured to supply alternating currents to the K stages of optical amplifiers, and
a laser controller configured to control the master oscillator and the K optical-amplifier power supplies,

wherein each of a part of the optical amplifiers including the K-th stage optical amplifier includes:
a power supply control circuit configured to output gate signals with pulse width corresponding to command values received from the laser controller; and
an inverter circuit configured to change output amplitude in accordance with the pulse width of the gate signals output from the power supply control circuit, and

wherein each of the part of the optical amplifiers including the K-th stage optical amplifier is configured to supply the alternating current corresponding to each command value received from the laser controller.

7. The EUV light generation system according to claim 6 , wherein an exciting frequency of each of the K stages of optical amplifiers is equal to or higher than an EUV light generation frequency.

8. The EUV light generation system according to claim 7 ,
wherein the laser controller is configured to:
calculate a difference between a measured value of energy of EUV light in the chamber and a target value of the EUV light; and
correct command values for the part of the optical amplifiers based on the difference.

9. The EUV light generation system according to claim 8 , wherein the power supply control circuit is configured to hold control information defining correspondence relations between command values from the laser controller and pulse width of gate signals.

10. The EUV light generation system according to claim 9 , wherein the laser controller is configured to acquire a measured value of output energy of each of the part of the optical amplifiers, calculate a difference between the measured value of the output energy and a target value of the output energy, and correct the control information based on the difference.

11. The EUV light generation system according to claim 7 ,
wherein the laser controller is configured to:
calculate a difference between a measured value of energy of EUV light in the chamber and a target value of the EUV light;
correct only a command value for the K-th stage optical amplifier based on the difference in a case where the difference is equal to or smaller than a threshold; and
correct command values for a plurality of optical amplifiers including the K-th stage optical amplifier in a case where the difference is larger than the threshold.

12. The EUV light generation system according to claim 11 , wherein, correcting the command values for the plurality of optical amplifiers including the K-th stage optical amplifier, compensations in command values for the optical amplifiers different from the K-th stage optical amplifier are fixed independent from the difference.

13. The EUV light generation system according to claim 7 , further comprising a current monitor configured to monitor the alternating current,
wherein the laser controller is configured to compare the command value and an output value of the current monitor to determine a deterioration level of laser gas.

14. The EUV light generation system according to claim 7 , wherein an interface between the laser controller and the power supply control circuit is configured with parallel I/O.

15. A control method for a laser apparatus configured to generate a pulse laser beam,
the laser apparatus including:
a master oscillator configured to output a pulse laser beam;
an optical amplifier configured to amplify the laser beam outputted from the master oscillator; and
an optical-amplifier power supply configured to supply an alternating current generated to the output of the optical amplifier,

the control method comprising:
acquiring a command value for the optical-amplifier power supply;
create a gate signal with pulse width corresponding to the command value;
changing output amplitude of the alternating current in accordance with the pulse width of the gate signal; and
supplying the alternating current with output amplitude corresponding to each newly received command value.

Assignees

• Gigaphoton Inc

Inventors

• Kawasuji Yasufumi
• Takaoka Naoya
• Yokozuka Toshio

Classifications

• H10P76/00

  Manufacture or treatment of masks on semiconductor bodies, e.g. by lithography or photolithography · CPC title

• H10P72/0436

  mainly by radiation · CPC title

• H01S3/09

  Processes or apparatus for excitation, e.g. pumping · CPC title

• H01S5/4012

  Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms · CPC title

• H01S3/104 Primary

  in gas lasers · CPC title