Laser device, and exposure device and inspection device provided with the laser device

Patent metadata

Field	Value
Publication number	US-2016240993-A1
Application number	US-201615137630-A
Country	US
Kind code	A1
Filing date	Apr 25, 2016
Priority date	Oct 25, 2013
Publication date	Aug 18, 2016
Grant date	—

Abstract

A laser device includes: a laser light source which generates a laser light in a pulse waveform of preset predetermined frequency; intensity modulator which is driven with a transmittance waveform wherein transmittance changes at either the predetermined frequency or an integer-multiple frequency thereof and which extracts and outputs the laser light which is outputted from the laser light source; control unit which controls an operation of the intensity modulator; an amplifier which amplifies the laser light which is outputted from the intensity modulator; and a wavelength conversion optical element which converts a wavelength of the laser light which is amplified by the amplifier, wherein the control unit changes relative timing of the transmittance waveform with respect to the pulse waveform, thereby changing the pulse waveform of the laser light which is emitted from the intensity modulator, to output a pulse light of predetermined waveform from the wavelength conversion optical element.

First claim

What is claimed is:

1 . A laser device comprising:
a laser light source which generates a laser light in a pulse waveform of a preset predetermined frequency; an intensity modulator which is driven with a transmittance waveform wherein transmittance changes at either the predetermined frequency or an integer-multiple frequency thereof and which extracts and outputs the laser light which is outputted from the laser light source; a control unit which controls an operation of the intensity modulator; an amplifier which amplifies the laser light which is outputted from the intensity modulator; and a wavelength conversion optical element which converts a wavelength of the laser light which is amplified by the amplifier, wherein the control unit changes relative timing of the transmittance waveform with respect to the pulse waveform, thereby changing the pulse waveform of the laser light which is emitted from the intensity modulator, to output a pulse light of a predetermined waveform from the wavelength conversion optical element.

2 . The laser device according to claim 1 , wherein
the laser light which is outputted from the intensity modulator includes either a laser light in a first pulse waveform of the predetermined frequency or a laser light in a second pulse waveform of the predetermined frequency which has different timing with respect to that of the laser light in the first pulse waveform, the laser light in the first pulse waveform is a light which is set so that an efficiency of wavelength conversion at the wavelength conversion optical element is relatively high so as to generate the pulse light, the laser light in the second pulse waveform is a light which is set to have energy substantially the same as that of the laser light in the first pulse waveform and a relatively low efficiency of wavelength conversion at the wavelength conversion optical element so as not to generate the pulse light.

3 . The laser device according to claim 2 , wherein
the laser light source includes a first laser light source that generates a laser light in the first pulse waveform of the predetermined frequency and a second laser light source which generates a laser light in a second pulse waveform of the predetermined frequency at timing different from timing at which the laser light in the first pulse waveform is generated, the laser light in the first pulse waveform which is outputted from the first laser light source and the laser light in the second pulse waveform which is outputted from the second laser light source are multiplexed and inputted into the intensity modulator, the transmittance waveform is an on/off gate-like waveform which is switched between a transmission state in which the laser light is transmitted at the predetermined frequency and a shutoff state in which the laser light is shutoff, and the control unit changes relative timing of the transmittance waveform with respect to the first pulse waveform and the second pulse waveform, thereby changing the pulse waveform of the laser light which is transmitted through the intensity modulator.

4 . The laser device according to claim 3 , wherein
the laser light in the first pulse waveform and the laser light in the second pulse waveform differ in peak intensity from each other.

5 . The laser device according to claim 3 , wherein
the laser light in the first pulse waveform and the laser light in the second pulse waveform differ in wavelength from each other.

6 . The laser device according to claim 3 , wherein
the laser light in the first pulse waveform and the laser light in the second pulse waveform differ in a state of polarization upon entering the wavelength conversion optical element from each other.

7 . The laser device according to claim 3 , wherein
the first laser light source and the second laser light source are each a semiconductor laser.

8 . The laser device according to claim 3 , wherein
the first laser light source is a mode-locked laser which generates the laser light in the first pulse waveform at the predetermined frequency and the second laser light source is a semiconductor laser, the laser device comprises a photodetector which detects the laser light in the first pulse waveform which is outputted from the mode-locked laser; and a synchronization circuit which, based on the first pulse waveform which is detected by the photodetector, outputs a synchronization signal to a drive power source of the second laser light source and to the control unit.

9 . The laser device according to claim 3 , wherein
the laser light in the first pulse waveform which is outputted from the first laser light source and the laser light in the second pulse waveform which is outputted from the second laser light source are once multiplexed and then divided into a plurality of branch optical paths, each of the intensity modulator, the wavelength conversion optical element, and the amplifier is provided at each of the plurality of branch optical paths, the control unit changes the relative timing of the transmittance waveform with respect to the first pulse waveform and the second pulse waveform for each branch optical path, thereby enabling each of the waveform conversion optical elements to output a plurality of pulse lights of different pulse waveforms.

10 . The laser device according to claim 2 , wherein
the laser light source is a light source that generates a laser light of a base waveform at the predetermined frequency, the transmittance waveform is a high and low gate-like waveform in which a first transmittance waveform which has a relatively high transmittance and with which the laser light in the first pulse waveform is extracted from the laser light of the base waveform and a second transmittance waveform which has a relatively low transmittance and with which the laser light in the second pulse waveform is extracted from the laser light of the base waveform are alternately repeated each at the predetermined frequency, and the control unit changes relative timing of the transmittance waveform with respect to the base waveform, thereby changing the pulse waveform of the laser light that is transmitted through the intensity modulator.

11 . The laser device according to claim 2 , wherein
the laser light source includes a first laser light source that generates a laser light of a first base waveform at the predetermined frequency and a second laser light source that generates a laser light of a second base waveform at the predetermined frequency and at different timing from that at which the laser light of the first base waveform is generated, the laser light of the first base waveform which is outputted from the first laser light source and the laser light of the second base waveform which is outputted from the second laser light source are multiplexed and inputted into the intensity modulator, the transmittance waveform is a gate-like waveform in which a first transmittance waveform with which the laser light in the first pulse waveform is extracted from the laser light of the first base waveform and a second transmittance waveform with which the laser light in the second pulse waveform is extracted from the laser light of the second base waveform are alternately repeated each at the predetermined frequency, the control unit changes relative timing of the transmittance waveform with respect to the first base waveform and the second base waveform, thereby changing the pulse waveform of the laser light that is transmitted through the intensity modulator.

12 . The laser device according to claim 11 , wherein
the laser light in the first pulse waveform and the las

Assignees

• Nikon Corp

Inventors

• Tokuhisa Akira

Classifications

• G03F7/70025

  by lasers · CPC title

• H01S3/0085

  Modulating the output, i.e. the laser beam is modulated outside the laser cavity · CPC title

• H01S3/0092

  Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity (nonlinear frequency conversion per se G02F1/35) · CPC title

• H01S3/1618

  ytterbium · CPC title

• H01S3/06754 Primary

  Fibre amplifiers (H01S3/06708 takes precedence) · CPC title