Laser system

• US 7,999,915 B2
• Filed: 10/30/2007
• Issued: 08/16/2011
• Est. Priority Date: 11/01/2005
• Status: Active Grant

• Current Assignee: Cymer Incorporated (ASML Holding NV)
• Original Assignee: Cymer Incorporated (ASML Holding NV)
• Inventors: Lalovic, Ivan, Brown, Daniel J. W., Bergstedt, Robert A., Fomenkov, Igor V., Ershov, Alexander I., Partlo, William N.
• Primary Examiner(s): Nguyen; Hung Henry
• Assistant Examiner(s): KREUTZER, COLIN WRIGHT
• Application Number:
  US11/981,450
• Publication Number:
  US 20080165337A1
• Time in Patent Office: 1,386 Days
• Field of Search: 355/35, 355/53, 355/67, 355/77, 355/71, 372/25, 372/29.016, 372/29.023, 372/30, 372/55, 372/57, 372/700
• US Class Current: 355/67
• CPC Class Codes: G03F 7/70025 by lasers
• CPC Class Codes: G03F 7/70583 Speckle reduction, e.g. coherence control or amplitude/wavefront splitting
• CPC Class Codes: G03F 7/70616 Monitoring the printed patterns
• CPC Class Codes: G03F 7/70625 Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness
• CPC Class Codes: H01S 3/08004 incorporating a dispersive element, e.g. a prism for wavelength selection H01S3/0811, H01S3/08022 take precedence
• 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 3/225 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 3/2308 Amplifier arrangements, e.g. MOPA

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 method comprising:

reducing feature dimension roughness in an exposed photoresist layer exposed by a pulsed light source comprising;

producing a pulsed seed laser output from a seed laser of the light source;

separating the pulsed seed laser output into a main beam of sub pulses and a delayed beam of sub pulses entering an optical delay path having a delay length longer than the coherence length of a pulse in the seed laser output;

angularly offsetting the delayed beam relative to the main beam in the far field by an amount that is less than a divergence of the main beam;

recombining the main beam of sub pulses and the offset delayed beam of sub pulses into a mixed beam of sub pulses; and

directing the mixed beam into an amplification gain stage of the light source.

2. An apparatus comprising:

a mechanism reducing feature dimension roughness in an exposed photoresist layer exposed by a pulsed light source comprising;

a laser light source comprising a seed laser producing a pulsed seed laser output and an amplification gain stage;

a coherence busting mechanism intermediate the seed laser and the amplification stage comprising at least one beam splitter separating the seed laser output into a main beam of sub pulses and at least one delayed beam of sub pulses entering an optical delay path having a delay length longer than the coherence length of a pulse in the seed laser output;

a beam angular offset mechanism angularly offsetting the delayed beam from the main beam in the far field by an amount that is less than a divergence of the main beam; and

a beam combiner combining the angularly offset delayed beam and the main beam as a mixed beam that is received by the amplification gain stage.

3. A method comprising:

reducing feature dimension roughness in an exposed photoresist layer exposed by a pulsed sub-400 nm light source comprising;

producing a pulsed seed laser output from a seed laser of the light source;

separating the pulsed seed laser output into a main beam of sub pulses, a first delayed beam of sub pulses entering a first optical delay path having a delay length longer than the coherence length of a pulse in the seed laser output, and a second delayed beam of sub pulses entering a second optical delay path that is distinct from the first optical delay path;

angularly offsetting the first delayed beam relative to the main beam in the far field by an amount that is less than a divergence of the main beam;

angularly offsetting the second delayed beam relative to the main beam in the far field by an amount that is less than a divergence of the main beam;

recombining the main beam of sub pulses, the first offset delayed beam of sub pulses, and the second offset delayed beam of sub pulses into a mixed beam of sub pulses; and

directing the mixed beam into an amplification gain stage of the light source.

4. The method of claim 3 wherein each sub-pulse in the first delayed beam is delayed substantially less than its pulse length such that the delay creates substantially no increase in the pulse length.

5. The method of claim 3 wherein each sub-pulse in the first delayed beam is delayed substantially less than its pulse length such that the delay creates substantially no increase in the total integrated spectrum of the pulse.

6. The method of claim 3 wherein each sub-pulse in second the delayed beam is delayed substantially less than its pulse length such that the delay creates substantially no increase in the total integrated spectrum of the pulse.

7. The method of claim 3, wherein angularly offsetting the first delayed beam from the main beam comprises angularly offsetting the first delayed beam from the main beam in a first axis using a first mechanism and angularly offsetting the second delayed beam from the main beam comprises angularly offsetting the second delayed beam from the main beam in a second axis using a second mechanism.

8. The method of claim 7 wherein the first axis is different from the second axis.

9. The method of claim 3 further comprising:

utilizing a coherence busting mechanism located in a photolithography tool intermediate an illuminator and a wafer.

10. The method of claim 3 further comprising:

utilizing a coherence busting mechanism located in a photolithography tool intermediate a light source light entry opening and an illuminator.

11. The method of claim 3 further comprising:

utilizing a coherence busting mechanism located intermediate a photolithography tool and a laser light source.

12. The method of claim 3 further comprising:

utilizing a coherence busting mechanism within a laser light source system intermediate a laser and an OPuS.

13. The method of claim 3 further comprising:

utilizing a coherence busting mechanism within a laser light source system intermediate an OPuS and a photolithography tool.

14. The method of claim 3 further comprising:

another coherence busting mechanism intermediate an illuminator and the photoresist layer.

15. The method of claim 3 wherein angularly offsetting the first delayed beam from the main beam in the far field includes misaligning one or more mirrors within the optical delay path.

16. The method of claim 3 wherein angularly offsetting the first delayed beam from the main beam in the far field includes placing a wedge in the optical delay path.

17. An apparatus comprising:

a mechanism reducing feature dimension roughness in an exposed photoresist layer exposed by a pulsed sub-400 nm light source comprising;

a laser light source comprising a seed laser producing a pulsed seed laser output and an amplification gain stage;

a coherence busting mechanism intermediate the seed laser and the amplification stage comprising two beam splitters separating the seed laser output into a main beam of sub pulses, a first delayed beam of sub pulses entering a first optical delay path having a delay length longer than the coherence length of a pulse in the seed laser output, and a second delayed beam of sub pulses entering a second optical delay path that is distinct from the first optical delay path;

a first beam angular offset mechanism in the first optical delay path angularly offsetting the first delayed beam from the main beam in the far field by an amount that is less than a divergence of the main beam; and

a second beam angular offset mechanism in the second optical delay path angularly offsetting the second delayed beam from the main beam in the far field by an amount that is less than a divergence of the main beam; and

a beam combiner combining the first angularly offset delayed beam, the second angularly offset delayed beam, and the main beam as a mixed beam that is received by the amplification gain stage.

18. The apparatus of claim 17 wherein the coherence busting mechanism comprises a first coherence busting optical delay structure and a second coherence busting optical delay structure.

19. The apparatus of claim 18 wherein the optical delay time in the second coherence busting optical delay structure is longer than the optical delay time in the first coherence busting optical delay structure by more than the coherence length of the input light pulse.

20. The apparatus of claim 17 wherein the first beam angular offset mechanism offsets the first delayed beam from the main beam in a first axis and the second beam angular offset mechanism offsets the second delayed beam from the main beam in a second axis.

21. The apparatus of claim 17 wherein the first beam angular offset mechanism includes a misalignment of one or more mirrors within the first optical delay path.

22. The apparatus of claim 17 wherein the first beam angular offset mechanism includes a wedge placed in the first optical delay path.

23. The apparatus of claim 17 wherein the second beam angular offset mechanism includes a misalignment of one or more mirrors within the second optical delay path.

24. The apparatus of claim 17 wherein the second beam angular offset mechanism includes a wedge placed in the second optical delay path.