Laser system

• US 7,822,092 B2
• Filed: 10/30/2007
• Issued: 10/26/2010
• Est. Priority Date: 11/01/2005
• Status: Active Grant

• Current Assignee: Cymer Incorporated (ASML Holding NV)
• Original Assignee: Cymer Incorporated (ASML Holding NV)
• Inventors: Brown, Daniel J. W., Bergstedt, Robert A., Fomenkov, Igor V., Ershov, Alexander I., Partlo, William N.
• Primary Examiner(s): Harvey; Minsun
• Assistant Examiner(s): Zhang; Yuanda
• Application Number:
  US11/981,014
• Publication Number:
  US 20080144671A1
• Time in Patent Office: 1,092 Days
• Field of Search: 372/55, 372/57, 372/60, 372/61, 372/69, 372/70, 372/71, 372/72, 372/93, 372/94
• US Class Current: 372/55
• CPC Class Codes: G03F 7/70583 Speckle reduction, e.g. coherence control or amplitude/wavefront splitting
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/0057 Temporal shaping, e.g. pulse compression, frequency chirping soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108
• CPC Class Codes: H01S 3/03 of gas laser discharge tubes
• CPC Class Codes: H01S 3/034 Optical devices within, or forming part of, the tube, e.g. windows, mirrors reflectors having variable properties or positions for initial adjustment of the resonator H01S3/086
• CPC Class Codes: H01S 3/08036 using intracavity dispersive, polarising or birefringent elements
• CPC Class Codes: H01S 3/08059 Constructional details of the reflector, e.g. shape mirrors in general G02B5/08; mountings for mirrors G02B7/18
• CPC Class Codes: H01S 3/10092 Coherent seed, e.g. injection locking
• CPC Class Codes: H01S 3/105 by controlling the mutual position or the reflecting properties of the reflectors of the cavity , e.g. by controlling the cavity lengthH01S3/10076, H01S3/13 take precedence
• CPC Class Codes: H01S 3/225 comprising an excimer or exciplex
• CPC Class Codes: H01S 3/2251 ArF, i.e. argon fluoride is comprised for lasing around 193 nm
• CPC Class Codes: H01S 3/2333 Double-pass amplifiers

Abstract

A method and apparatus may comprise a line narrowed pulsed excimer or molecular fluorine gas discharge laser system which may comprise a seed laser oscillator producing an output comprising a laser output light beam of pulses which may comprise a first gas discharge excimer or molecular fluorine laser chamber; a line narrowing module within a first oscillator cavity; a laser amplification stage containing an amplifying gain medium in a second gas discharge excimer or molecular fluorine laser chamber receiving the output of the seed laser oscillator and amplifying the output of the seed laser oscillator to form a laser system output comprising a laser output light beam of pulses, which may comprise a ring power amplification stage.

Claims

1. A laser apparatus comprising:

a seed laser oscillator producing an output comprising a laser output light beam of pulses, the seed laser oscillator comprising;

a first gas discharge excimer or molecular fluorine laser chamber;

a laser amplification stage containing an amplifying gain medium in a second gas discharge excimer or molecular fluorine laser chamber receiving the output of the seed laser oscillator and amplifying the output of the seed laser oscillator to form a laser system output comprising a laser output light beam of pulses, the laser amplification stage comprising;

a ring power amplification stage comprising;

a beam expander; and

a partially reflecting optical element through which the seed laser oscillator output light beam is injected into the ring power amplification stage; and

a coherence busting mechanism intermediate the seed laser oscillator and the ring power amplification stage comprising an optical delay path having a delay length longer than the coherence length of a pulse in the seed laser oscillator laser output light beam of pulses;

wherein the beam expander is configured to de-magnify the laser beam as the laser beam travels from the partially reflecting optical element toward the amplifying gain medium and to expand the laser beam as the laser beam travels from the amplifying gain medium toward the partially reflecting optical element.

2. The apparatus of claim 1 further comprising:

the ring power amplification stage comprising a bow-tie loop.

3. The apparatus of claim 1 further comprising:

the ring power amplification stage comprising a race track loop.

4. The apparatus of claim 1 further comprising:

the pulse energy of the output of the seed laser oscillator being less than or equal to 1.0 mJ.

5. The apparatus of claim 1 further comprising:

the pulse energy of the output of the seed laser oscillator being less than or equal to 0.1 mJ.

6. The apparatus of claim 1 further comprising:

the ring power amplification stage amplifying the output of the seed laser oscillator cavity to a pulse energy of ≧

5 mJ.

7. The apparatus of claim 1 further comprising:

the ring power amplification stage amplifying the output of the seed laser oscillator to a pulse energy of ≧

15 mJ.

8. The apparatus of claim 1 further comprising:

the laser system operating at an output pulse repetition rate of up to 12 kHz.

9. The apparatus of claim 1 further comprising:

the laser system operating at an output pulse repetition rate of ≧

4 and ≦

6 kHz.

10. The apparatus of claim 1 wherein the beam expander comprises at least one prism.

11. The apparatus of claim 1 wherein the beam expander comprises a two prism beam expander.

12. The apparatus of claim 1 wherein the ring power amplification stage is defined between a beam reverser and the partially reflecting optical element.

13. The apparatus of claim 12 wherein the beam reverser comprises a prism that is configured to cross a light beam traveling along a first path through the amplifying gain medium with a light beam traveling along a second path through the amplifying gain medium.

14. The apparatus of claim 1 wherein the seed laser oscillator comprises a line narrowing module within a first oscillator cavity.

15. A laser apparatus comprising:

a seed laser oscillator producing an output comprising a laser output light beam of pulses, the seed laser oscillator comprising;

a first gas discharge excimer or molecular fluorine laser chamber;

a laser amplification stage containing an amplifying gain medium in a second gas discharge excimer or molecular fluorine laser chamber receiving the output of the seed laser oscillator and amplifying the output of the seed laser oscillator to form a laser system output comprising a laser output light beam of pulses, the laser amplification stage comprising;

a ring power amplification stage comprising;

a beam expander comprising a two prism beam expander; and

a partially reflecting optical element through which the seed laser oscillator output light beam is injected into the ring power amplification stage; and

a coherence busting mechanism intermediate the seed laser oscillator and the ring power amplification stage comprising an optical delay path having a delay length longer than the coherence length of a pulse in the seed laser oscillator laser output light beam of pulses;

wherein the first prism of the two prism beam expander comprises a split prism and the second prism of the two prism beam expander comprises a one piece prism.