Optical pulse stretcher, laser apparatus, and electronic device manufacturing method

1 . An optical pulse stretcher that stretches a pulse width of a pulse laser beam, the optical pulse stretcher comprising:

a polarizer configured to separate a component in a specific polarization direction of the pulse laser beam that has entered;

a delay optical system including a plurality of mirrors that are configured such that the pulse laser beam reflected by or transmitted through the polarizer passes through a delay optical path, through which the pulse laser beam is propagated to return to the polarizer, a plurality of times; and

a first Faraday rotator that includes a first magnet and a first Faraday material and is disposed on the delay optical path of the delay optical system to rotate a polarization direction of the pulse laser beam.

2 . The optical pulse stretcher according to claim 1 , further comprising:

a first actuator capable of changing a rotation amount in the polarization direction of the pulse laser beam in the first Faraday rotator; and

a processor configured to control the first actuator.

3 . The optical pulse stretcher according to claim 2 , wherein

the first actuator is a first moving mechanism configured to change a position in an optical axis direction of the pulse laser beam of the first Faraday material with respect to the first magnet.

4 . The optical pulse stretcher according to claim 1 , further comprising

a second Faraday rotator that includes a second magnet and a second Faraday material and is configured to rotate the polarization direction of the pulse laser beam entering the polarizer.

5 . The optical pulse stretcher according to claim 4 , further comprising:

a first actuator capable of changing a rotation amount in the polarization direction of the pulse laser beam in the first Faraday rotator;

a second actuator capable of changing a rotation amount in the polarization direction of the pulse laser beam in the second Faraday rotator; and

a processor configured to control the first actuator and the second actuator.

6 . The optical pulse stretcher according to claim 5 , wherein

the first actuator is a first moving mechanism configured to change a position in an optical axis direction of the pulse laser beam of the first Faraday material with respect to the first magnet, and

the second actuator is a second moving mechanism configured to change a position in the optical axis direction of the pulse laser beam of the second Faraday material with respect to the second magnet.

7 . The optical pulse stretcher according to claim 4 , wherein

each of the first Faraday material and the second Faraday material is calcium fluoride or synthetic quartz.

8 . The optical pulse stretcher according to claim 1 , wherein

the polarization direction of the pulse laser beam entering the optical pulse stretcher and a transmission axis of the polarizer are orthogonal to each other.

9 . The optical pulse stretcher according to claim 1 , wherein

the mirrors include four concave mirrors.

10 . A laser apparatus comprising:

an oscillator configured to output a pulse laser beam; and

an optical pulse stretcher configured to stretch a pulse width of the pulse laser beam,

the optical pulse stretcher including

a polarizer configured to separate a component in a specific polarization direction of the pulse laser beam that has entered,

a delay optical system including a plurality of mirrors that are configured such that the pulse laser beam reflected by or transmitted through the polarizer passes through a delay optical path, through which the pulse laser beam is propagated to return to the polarizer, a plurality of times; and

a first Faraday rotator that includes a first magnet and a first Faraday material and is disposed on the delay optical path of the delay optical system to rotate a polarization direction of the pulse laser beam.

11 . The laser apparatus according to claim 10 , further comprising:

a first actuator capable of changing a rotation amount in the polarization direction of the pulse laser beam; and

a processor configured to control the first actuator.

12 . The laser apparatus according to claim 11 , wherein the first actuator is a first moving mechanism configured to change a position in an optical axis direction of the pulse laser beam of the first Faraday material with respect to the first magnet.

13 . The laser apparatus according to claim 11 , further comprising a photosensor configured to measure a pulse waveform of the pulse laser beam having passed through the optical pulse stretcher, wherein

the processor calculates a pulse width from the pulse waveform, and controls the first actuator so that the pulse width becomes equal to or greater than a target value.

14 . The laser apparatus according to claim 11 , wherein

the processor uses table data indicating a relationship between a pulse width of the pulse laser beam having passed through the optical pulse stretcher and a control amount of the first actuator to control the first actuator so that the pulse width is equal to or greater than a target value.

15 . The laser apparatus according to claim 10 , wherein

the polarization direction of the pulse laser beam entering the optical pulse stretcher and a transmission axis of the polarizer are orthogonal to each other.

16 . The laser apparatus according to claim 10 , wherein

the oscillator includes a line narrowing optical system configured to narrow a spectral linewidth of the pulse laser beam having an ultraviolet wavelength.

17 . The laser apparatus according to claim 10 , wherein

the oscillator includes:

an oscillation stage laser configured to output a first pulse laser beam having an ultraviolet wavelength; and

an amplifier configured to amplify and output the first pulse laser beam output from the oscillation stage laser.

18 . The laser apparatus according to claim 10 , further comprising

a second Faraday rotator that includes a second magnet and a second Faraday material and is configured to rotate the polarization direction of the pulse laser beam entering the optical pulse stretcher.

19 . The laser apparatus according to claim 18 , further comprising:

a first actuator capable of changing a rotation amount in the polarization direction of the pulse laser beam in the first Faraday rotator;

a second actuator capable of changing a rotation amount in the polarization direction of the pulse laser beam in the second Faraday rotator; and

a processor configured to control the first actuator and the second actuator.

20 . An electronic device manufacturing method comprising:

generating a laser beam having a stretched pulse width with a laser apparatus, the laser apparatus including

an oscillator configured to output a pulse laser beam, and

an optical pulse stretcher configured to stretch a pulse width of the pulse laser beam, the optical pulse stretcher including

a polarizer configured to separate a component in a specific polarization direction of the pulse laser beam that has entered,

a delay optical system including a plurality of mirrors that are configured such that the pulse laser beam reflected by or transmitted through the polarizer passes through a delay optical path, through which the pulse laser beam is propagated to return to the polarizer, a plurality of times; and

a first Faraday rotator that includes a first magnet and a first Faraday material and is disposed on the delay optical path of the delay optical system to rotate a polarization direction of the pulse laser beam;

outputting the laser beam to an exposure apparatus; and

exposing a photosensitive substrate to the laser beam in the exposure apparatus to manufacture an electronic device.