183 nm CW laser and inspection system

Patent metadata

Field	Value
Publication number	US-10175555-B2
Application number	US-201715806953-A
Country	US
Kind code	B2
Filing date	Nov 8, 2017
Priority date	Jan 3, 2017
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

A laser assembly generates continuous wave (CW) laser output light in the range of approximately 181 nm to approximately 185 nm by generating fourth harmonic light from first fundamental CW light having a first fundamental wavelength between 1 μm and 1.1 μm, generating fifth harmonic light by mixing the fourth harmonic light with the first fundamental CW light, and then mixing the fifth harmonic light with second fundamental or signal CW light having a second wavelength between 1.26 μm and 1.82 μm. The fifth harmonic light is generated using an external cavity that circulates first fundamental CW light through a first nonlinear crystal, and by directing the fourth harmonic light through the first nonlinear crystal. The laser output light is generated using a second cavity that passes circulated second fundamental or signal CW light through a second nonlinear crystal, and directing the fifth harmonic light through the second nonlinear crystal.

First claim

The invention claimed is:

1. A laser assembly for generating continuous wave (CW) laser output light having a wavelength in the range of approximately 181 nm to approximately 185 nm, said laser assembly comprising:
a first fundamental CW laser configured to generate a first fundamental CW light having a first fundamental frequency with a corresponding first fundamental wavelength between about 1 μm and 1.1 μm;
a fourth harmonic generation module coupled to receive a first portion of the first fundamental CW light, and configured to generate a fourth harmonic light having a fourth harmonic frequency equal to four times the first fundamental frequency;
a fifth harmonic generation module coupled to receive a second portion of the first fundamental CW light and to receive said fourth harmonic light from the fourth harmonic generation module, said fifth harmonic generation module being configured to generate a fifth harmonic light having a fifth harmonic frequency equal to five times the first fundamental frequency by mixing said fourth harmonic light and said second portion of the first fundamental CW light;
a frequency mixing module configured to generate said laser output light by mixing said fifth harmonic light with a second CW light having a second frequency with a corresponding second wavelength between 1.26 μm and 1.82 μm,
wherein the fifth harmonic generation module comprises a first cavity and a first nonlinear crystal, said first cavity being formed by a plurality of first mirrors that are configured to circulate the second portion of the first fundamental CW light such that circulated said first fundamental light passes through the first nonlinear crystal, said first nonlinear crystal being configured to mix said circulated first fundamental light with said fourth harmonic light received directly from said fourth harmonic generator to generate said fifth harmonic light,
wherein the frequency mixing module comprises a second cavity and a second nonlinear crystal, said second cavity being formed by a plurality of second mirrors that are configured to circulate the second CW light such that the circulated second CW light passes through the second nonlinear crystal, and the second nonlinear crystal being configured to receive said fifth harmonic light directly from said fifth harmonic generator such that said fifth harmonic light mixes with said circulated second CW light to generate said laser output light, and
wherein at least one of the first and second nonlinear crystals comprises one of an annealed cesium lithium borate (CLBO) crystal, a hydrogen-treated CLBO crystal and a deuterium-treated CLBO crystal.

2. The laser assembly of claim 1 , further comprising a second fundamental laser configured to generate the second CW light at a first power level,
wherein the frequency mixing module is configured to receive the second CW light from the second fundamental laser such that the second CW light is circulated in the second cavity, and the second cavity is configured to resonate at a second fundamental frequency of said second CW light such that a second power level of the circulated second CW light is greater than the first power level.

3. The laser assembly of claim 2 , wherein the second fundamental laser comprises one of a Yb doped fiber laser, a Nd doped solid state laser, fiber laser or fiber amplifier, and an erbium (Er) doped solid state laser, fiber laser or fiber amplifier.

4. The laser assembly of claim 1 , further comprising a pump laser configured to generate second laser light at a first frequency,
wherein the second cavity comprises one of a solid state laser cavity and an optical parametric oscillator cavity, said second cavity being configured to generate the circulated second CW light using the second laser light received from the pump laser such that the circulated second CW light has a second frequency that is lower than the first frequency.

5. The laser assembly of claim 4 , wherein the frequency mixing module further comprises one of a Nd doped gain medium and an erbium (Er) doped gain medium.

6. The laser assembly of claim 4 , wherein the second cavity further comprises an optical diode and an etalon.

7. The laser assembly of claim 4 , wherein the frequency mixing module further comprises one of periodically poled magnesium-oxide doped stoichiometric lithium tantalate and periodically poled magnesium-oxide doped lithium niobate.

8. The laser assembly of claim 1 , wherein the first fundamental laser is configured such that the first fundamental frequency has a corresponding wavelength equal to one of approximately 1070 nm, approximately 1064 nm, approximately 1053 nm, approximately 1047 nm, and approximately 1030 nm.

9. The laser assembly of claim 1 , wherein the first fundamental laser comprises one of an ytterbium (Yb) doped fiber laser or fiber amplifier, a neodymium (Nd) doped solid state laser and a Nd doped fiber laser or fiber amplifier.

10. The laser assembly of claim 1 , wherein the fourth harmonic generation module comprises two frequency doubling cavity modules.

11. The laser assembly of claim 1 , wherein the fifth harmonic generation module is configured such that the fourth harmonic light and the circulated first fundamental light are transmitted collinearly through the first nonlinear crystal.

12. The laser assembly of claim 1 , wherein the frequency mixing module is configured to transmit the fifth harmonic light collinearly with the circulated second CW light through the second nonlinear crystal.

13. The laser assembly of claim 1 , further comprising means for maintaining the first nonlinear crystal at a constant temperature of approximately 80° C. or lower.

14. The laser assembly of claim 1 , further comprising means for maintaining second nonlinear crystal at a constant temperature of approximately 30° C. or lower.

15. The laser assembly of claim 1 , wherein the first fundamental laser is configured such that the first fundamental frequency has a corresponding wavelength equal to one of approximately 1064 nm and approximately 1070 nm, and wherein the second frequency has a corresponding wavelength in the range of approximately 1260 nm to approximately 1420 nm.

16. The laser assembly of claim 1 , wherein the first fundamental laser is configured such that the first fundamental frequency has a corresponding wavelength of approximately 1047 nm and approximately 1053 nm, and wherein the second frequency has a corresponding wavelength in the range of approximately 1290 nm to approximately 1590 nm.

17. The laser assembly of claim 1 , wherein the first fundamental laser is configured such that the first fundamental frequency has a corresponding wavelength of approximately 1030 nm, and wherein the second frequency has a corresponding wavelength in the range of approximately 1490 nm to approximately 1820 nm.

18. A method of generating continuous wave (CW) laser output light having a wavelength in the range of approximately 181 nm to approximately 185 nm, the method comprising:
generating a first fundamental light having a first fundamental frequency with a corresponding first fundamental wavelength between about 1 μm and 1.1 μm;
converting a first portion of the first fundamental light to a fourth harmonic light having a fourth harmonic frequency equal to four times the first fundamental frequency;
generating a fifth harmonic light having a fifth harmonic frequency equal to five times the first fundamental frequency by mixing a second portion of the first fundamental light and the fourth harmonic light, wherein said mixing com

Assignees

• Kla Tencor Corp
• Kla—Tencor Corp

Inventors

• Chuang Yung-Ho Alex
• Lu Xiaoxu
• Zhang Baigang
• Fielden John
• Dribinski Vladimir

Classifications

• G02F1/3558

  Poled materials, e.g. with periodic poling; Fabrication of domain inverted structures, e.g. for quasi-phase-matching [QPM] · CPC title

• G02F1/353 Primary

  Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams · CPC title

• G02F2201/16

  series; tandem · CPC title

• G02F1/3501

  Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals · CPC title

• G02F1/3551

  Crystals · CPC title