Deep ultra-violet light sources for wafer and reticle inspection systems

Patent metadata

Field	Value
Publication number	US-9318870-B2
Application number	US-201214114737-A
Country	US
Kind code	B2
Filing date	May 2, 2012
Priority date	May 6, 2011
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

Abstract

Disclosed are methods and apparatus for generating a sub-208 nm laser. A laser apparatus includes one or more seed radiation sources for generating a first radiation beam having a first fundamental wavelength on a first optical path and a second radiation beam having a second fundamental wavelength on a second optical path, a first amplifier for amplifying the first radiation beam, a second amplifier for amplifying the second radiation beam, and a wavelength conversion module comprising a plurality of crystals for frequency multiplying and mixing the amplified first and second radiation beams to produce an output beam at a fifth harmonic that is less than about 208 nm.

First claim

What is claimed is:

1. A laser apparatus for generating output radiation having a wavelength below about 208 nm, comprising:
one or more seed radiation sources for generating a first radiation beam having a first fundamental wavelength on a first optical path and a second radiation beam having a second fundamental wavelength on a second optical path, wherein the first radiation beam has a wavelength between 800-850 nm or 905-940 nm and the second radiation beam has a wavelength between about 980-1120 nm;
a first amplifier for amplifying the first radiation beam;
a second amplifier for amplifying the second radiation beam; and
a wavelength conversion module for frequency multiplying and mixing the amplified first and second radiation beams to produce an output beam at a fifth harmonic that is less than about 208 nm, wherein the wavelength conversion module comprises:
a 2nd harmonic generator (2HG) for receiving the second radiation beam and generating a 2nd harmonic beam by doubling a frequency of the second radiation beam;
a 3 rd harmonic generator (3HG) for receiving and mixing the 2 nd harmonic radiation beam with the second radiation beam to generate a 3rd harmonic beam;
a 4 th harmonic generator (4HG) for receiving and mixing the first radiation beam with the 3 rd harmonic beam to generate a 4 th harmonic beam; and
a fifth harmonic generator (5HG) for generating the output beam at a 5th harmonic that is less than about 208 nm by receiving and mixing the 4th harmonic radiation beam and the first radiation beam.

2. The laser apparatus of claim 1 , wherein the wavelength conversion module further comprises:
a plurality of mirrors for directing the 3rd harmonic radiation beam to merge with the first radiation beam of the first optical path.

3. The laser apparatus of claim 2 , wherein the first radiation beam has a wavelength between 800-850 nm, wherein the first amplifier is a TDFA and the second amplifier is a YDFA, wherein the 2HG is a PPLT crystal, the 3HG is a LBO crystal, the 4HG and 5HG are Rubidium fluoroberyllium borate (RBBF) crystals, wherein the 5 th harmonic is between 180-199 nm.

4. The laser apparatus of claim 2 , wherein the first radiation beam has a wavelength between 905-940 nm, wherein the first amplifier is a NDFA and the second amplifier is a YDFA, wherein the 2HG is a PPLT crystal, the 3HG is a BBO crystal, the 4HG and 5HG are RBBF crystals, wherein the 5 th harmonic reaches between 190-208 nm.

5. An inspection system for inspecting a photolithographic reticle or wafer for defects, comprising:
a laser apparatus as recited in any of claim 1 or 2 4 ;
imaging optics for directing the output beam towards a reticle or wafer;
a detector for receiving a detected signal or image in response to the output beam being reflected from or transmitted through the reticle or in response to the output beam being reflected from the wafer; and
a processor and memory that are configured to analyze the detected signal or image to thereby detect defects on the reticle or wafer.

6. A photolithography system for transferring a pattern from a reticle onto a wafer, comprising:
a laser apparatus as recited in claim 1 ; and
imaging optics for directing the output beam through a reticle onto a wafer.

7. A method of generating output radiation having a wavelength below about 208 nm, comprising:
generating a first radiation beam having a first fundamental wavelength on a first optical path and a second radiation beam having a second fundamental wavelength on a second optical path, wherein the first radiation beam has a wavelength between 800-850 nm or 905-940 nm and the second radiation beam has a wavelength between about 980-1120 nm;
amplifying the first radiation beam;
amplifying the second radiation beam; and
frequency multiplying and mixing the amplified first and second radiation beams to produce an output beam at a fifth harmonic that is less than about 208 nm, wherein the operation of multiplying and mixing is performed by:
a 2nd harmonic generator (2HG) for receiving the second radiation beam and generating a 2nd harmonic beam by doubling a frequency of the second radiation beam;
a 3 rd harmonic generator (3HG) for receiving and mixing the 2 nd harmonic radiation beam with the second radiation beam to generate a 3rd harmonic beam;
a 4 th harmonic generator (4HG) for receiving and mixing the first radiation beam with the 3 rd harmonic beam to generate a 4 th harmonic beam; and
a fifth harmonic generator (5HG) for generating the output beam at a 5th harmonic that is less than about 208 nm by receiving and mixing the 4th harmonic radiation beam and the first radiation beam.

8. The method of claim 7 , wherein the operation for multiplying and mixing is performed by:
a plurality of mirrors for directing the 3rd harmonic radiation beam to merge with the first radiation beam.

9. The method of claim 8 , wherein the first radiation beam has a wavelength between 800-850 nm, wherein the first amplifier is a TDFA and the second amplifier is a YDFA, wherein the 2HG is a PPLT crystal, the 3HG is a LBO crystal, the 4HG and 5HG are RBBF crystals, wherein the 5 th harmonic is between 180-199 nm.

10. The method of claim 8 , wherein the first radiation beam has a wavelength between 905-940 nm, wherein the first amplifier is a NDFA and the second amplifier is a YDFA, wherein the 2HG is a PPLT crystal, the 3HG is a BBO crystal, the 4HG and 5HG are RBBF crystals, wherein the 5 th harmonic is between 190-208 nm.

Assignees

• Lei Gang
• Kvamme Damon F
• Kla Tencor Corp

Inventors

• Lei Gang
• Kvamme Damon F

Classifications

• H01S3/2391 Primary

  emitting at different wavelengths · CPC title

• G02F1/353

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

• G02F2001/3507

  Physics · mapped topic

• H01S3/06754

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

• H01S3/109 Primary

  Frequency multiplication, e.g. harmonic generation · CPC title