183NM laser and inspection system

Patent metadata

Field	Value
Publication number	US-10199149-B2
Application number	US-201715659981-A
Country	US
Kind code	B2
Filing date	Jul 26, 2017
Priority date	Oct 3, 2014
Publication date	Feb 5, 2019
Grant date	Feb 5, 2019

Abstract

A laser assembly for generating laser output light at an output wavelength of approximately 183 nm includes a fundamental laser, an optical parametric system (OPS), a fifth harmonic generator, and a frequency mixing module. The fundamental laser generates fundamental light at a fundamental frequency. The OPS generates a down-converted signal at a down-converted frequency. The fifth harmonic generator generates a fifth harmonic of the fundamental light. The frequency mixing module mixes the down-converted signal and the fifth harmonic to produce the laser output light at a frequency equal to a sum of the fifth harmonic frequency and the down-converted frequency. The OPS generates the down-converted signal by generating a down-converted seed signal at the down-converted frequency, and then mixing the down-converted seed signal with a portion of the fundamental light. At least one of the frequency mixing, frequency conversion or harmonic generation utilizes an annealed, deuterium-treated or hydrogen-treated CLBO crystal.

First claim

The invention claimed is:

1. A laser assembly for generating laser output light having an output wavelength in a range between approximately 180 nm and approximately 185 nm, the laser assembly comprising:
a fundamental laser configured to generate fundamental light having a fundamental frequency;
an optical parametric system (OPS) coupled to the fundamental laser such that said OPS receives a first portion of the fundamental light, and said OPS is configured to generate a down-converted signal having a down-converted frequency that is less than the fundamental frequency;
a fifth harmonic generator coupled to the fundamental laser such that the fifth harmonic generator receives a second portion of the fundamental light, and said fifth harmonic generator is configured to generate fifth harmonic light having a fifth harmonic frequency equal to five times the fundamental frequency; and
a frequency mixing module that is optically coupled to receive the down-converted signal from the OPS and the fifth harmonic light from the fifth harmonic generator, and configured to generate said laser output light by mixing said down-converted signal and said fifth harmonic light,
wherein the OPS comprises:
a down-converted seed signal generator configured to generate a down-converted seed signal having said down-converted frequency and a first power level; and
an optical parametric amplifier (OPA) configured such that said down-converted seed signal and a portion of said fundamental light are mixed by passing once through a non-linear crystal, wherein said non-linear crystal is configured such that said mixing generates said down-converted signal at a second power level that is greater than ten times said first power level, and

wherein the OPS is configured such that a sum of said down-converted frequency and said fifth harmonic frequency produces said laser output light in the range between approximately 180 nm and approximately 185 nm.

2. The laser assembly of claim 1 , wherein the fundamental laser is configured to generate said fundamental light at said fundamental frequency having a corresponding wavelength equal to one of approximately 1064 nm, approximately 1053 nm, approximately 1047 nm, and approximately 1030 nm.

3. The laser assembly of claim 1 , wherein at least one of the fifth harmonic generator and the frequency mixing module comprises one of an annealed CLBO crystal, a deuterium-treated CLBO crystal and a hydrogen-treated CLBO crystal.

4. The laser assembly of claim 1 , wherein the OPA comprises:
a beam combiner configured to combine said first portion of said fundamental light with said down-converted seed signal;
a non-linear crystal configured to receive and amplify said down-converted seed signal by stimulated down-conversion of the first portion of said fundamental light; and
a beam splitter configured to separate said down-converted signal from other frequencies received from said non-linear crystal, and to direct said down-converted signal to said frequency mixing module.

5. The laser assembly of claim 4 , wherein the down-converted seed signal generator is configured to generate said down-converted seed signal at said first power level in the range of 1 mW to 500 mW, and wherein said OPA is configured to generate said down-converted signal at said second power level in the range of 1 W to 20 W.

6. The laser assembly of claim 4 , wherein beam combiner is further configured to reflect a first wavelength while transmitting a second wavelength such that said fundamental light portion and said down-converted seed signal are transmitted collinearly through said non-linear crystal.

7. The laser assembly of claim 6 , wherein the non-linear crystal comprises one of periodically poled lithium niobate (PPLN), periodically poled magnesium-oxide doped lithium niobate, periodically poled stoichiometric lithium tantalate (PPSLT), periodically poled magnesium-oxide doped stoichiometric lithium tantalate, and periodically poled potassium titanyl phosphate (PPKTP).

8. The laser assembly of claim 1 , wherein the down-converted seed signal generator of the OPS comprises a diode laser.

9. The laser assembly of claim 1 ,
wherein the OPS further comprises a beam splitter configured to split said first portion of said fundamental light into a first sub-portion and a second sub-portion,
wherein said down-converted seed signal generator comprises an optical parametric oscillator (OPO) configured to generate said down-converted seed signal by converting said first sub-portion; and
wherein said OPA is configured to mix said down-converted seed signal with said second sub-portion.

10. The laser assembly of claim 9 ,
wherein said down-converted signal has a down-converted wavelength corresponding to said down-converted frequency,
wherein said OPO comprises a first focusing mirror, a non-linear crystal, a second focusing mirror, a wavelength selector, and an output coupler that are operably configured to form a cavity in which light is reflected between said wavelength selector and said output coupler by way of said first and second focusing mirrors and said non-linear crystal,
wherein said wavelength selector is configured to be reflective for light having wavelengths in a wavelength range of approximately 0.2 nm centered on said down-converted wavelength, and
wherein said output coupler is configured to pass a portion of said light reflected between said wavelength selector and said output coupler as said down-converted seed signal.

11. The laser assembly of claim 10 , wherein said OPS comprises:
a beam combiner configured to combine said second sub-portion with said down-converted seed signal; and
a non-linear crystal configured to amplify said down-converted seed signal by stimulated down-conversion of the second sub-portion,
wherein an optical path length from beam splitter to said beam combiner is set such that pulses of said second sub-portion arrive at said beam combiner at the same time as pulses of said down-converted seed signal.

12. The laser assembly of claim 1 , wherein said optical parametric system is configured such that the down-converted signal has a signal wavelength in the range of approximately 1250 nm to approximately 1830 nm.

13. The laser assembly of claim 12 , wherein the fundamental laser is configured such that the fundamental frequency has a corresponding wavelength of approximately 1064.4 nm, and wherein the optical parametric system is configured such that the down-converted signal has a signal wavelength in the range of approximately 1250 nm to approximately 1420 nm.

14. The laser assembly of claim 12 , wherein the fundamental laser is configured such that the fundamental frequency has a corresponding wavelength of approximately 1030 nm, and wherein the optical parametric system is configured such that the down-converted signal has a signal wavelength in the range of approximately 1400 nm to approximately 1830 nm.

15. The laser assembly of claim 12 , wherein the fundamental laser comprises one of a mode-locked laser, a quasi-continuous-wave laser, laser diode and a fiber laser.

16. An inspection system comprising:
a laser assembly configured to generate laser output light having an output wavelength in a range between approximately 180 nm and approximately 185 nm;
first optics configured to direct the laser output light from the laser assembly to an object being inspected;
second optics configured to collect an image portion of said laser output light affected by the object being inspected, and to direct the image portion to one or more sensors,
wherein the laser asse

Assignees

• Kla Tencor Corp

Inventors

• Chuang Yung-Ho Alex
• Armstrong J Joseph
• Deng Yujun
• Dribinski Vladimir
• Fielden John
• Zhang Jidong

Classifications

• H01S5/0071

  for beam steering, e.g. using a mirror outside the cavity to change the beam direction · CPC title

• G01N2021/95676

  Masks, reticles, shadow masks · CPC title

• H01S5/0085

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

• G02F2/02

  Frequency-changing of light, e.g. by quantum counters · CPC title

• H01S5/0604

  comprising a non-linear region, e.g. generating harmonics of the laser frequency · CPC title