Laser system

• US 7,715,459 B2
• Filed: 10/31/2007
• Issued: 05/11/2010
• Est. Priority Date: 11/01/2005
• Status: Expired due to Fees

• Current Assignee: Cymer Incorporated (ASML Holding NV)
• Original Assignee: Cymer Incorporated (ASML Holding NV)
• Inventors: Sandstrom, Richard L., Brown, Daniel J. W., Partlo, William N.
• Primary Examiner(s): Nguyen; Dung T
• Application Number:
  US11/982,152
• Publication Number:
  US 20080267241A1
• Time in Patent Office: 923 Days
• Field of Search: 372/55, 372/57
• US Class Current: 372/55
• CPC Class Codes: G03F 7/70025 by lasers
• CPC Class Codes: G03F 7/70041 by pulsed sources, e.g. multiplexing, pulse duration, interval control or intensity control
• CPC Class Codes: G03F 7/7055 Exposure light control in all parts of the microlithographic apparatus, e.g. pulse length control or light interruption
• CPC Class Codes: G03F 7/70575 Wavelength control, e.g. control of bandwidth, multiple wavelength, selection of wavelength or matching of optical components to wavelength
• 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 3/08036 using intracavity dispersive, polarising or birefringent elements
• CPC Class Codes: H01S 3/225 comprising an excimer or exciplex
• CPC Class Codes: H01S 3/2308 Amplifier arrangements, e.g. MOPA
• CPC Class Codes: H01S 3/2325 Multi-pass amplifiers, e.g. regenerative amplifiers
• CPC Class Codes: H01S 3/2383 Parallel arrangements

Abstract

An apparatus/method which may comprise: a very high power line narrowed lithography laser light source which may comprise: a solid state seed laser system which may comprise: a pre-seed laser providing a pre-seed laser output; a fiber amplifier receiving the pre-seed laser output and providing an amplified seed laser pulse which may comprise: a pulse having a nominal wavelength outside of the DUV range; a frequency converter converting to essentially the wavelength of the amplifier gain medium; a first and a second gas discharge laser amplifier gain medium operating at different repetition rates from that of the seed laser output; a beam divider providing the amplifier gain mediums with output pulses from the seed laser; a beam combiner combining the outputs of each respective amplifier gain medium to provide a laser output light pulse beam having the pulse repetition rate of the solid state seed laser system.

Claims

1. An apparatus comprising:

a very high power line narrowed lithography laser light source comprising;

a solid state seed laser system comprising;

a pre-seed laser providing a pre-seed laser output;

a fiber amplifier receiving the pre-seed laser output and providing

an amplified seed laser pulse comprising;

a pulse having a nominal wavelength outside of the DUV range;

a frequency converter modifying the nominal center wavelength of the output of the seed laser system to essentially the nominal center wavelength of the amplifier gain medium;

a first and a second gas discharge laser amplifier gain medium each operating at a different pulse repetition rate from that of the seed laser output;

a beam divider providing each respective first and second amplifier gain medium with output pulses from the seed laser;

a beam combiner combining the outputs of each respective amplifier gain medium to provide a laser output light pulse beam having the pulse repetition rate of the solid state seed laser system.

2. The apparatus of claim 1 further comprising:

the seed laser is selected from the group comprising Nd⁺³ doped fiber lasers and Yb⁺³ doped fiber lasers.

3. The apparatus of claim 2 further comprising:

the seed laser comprising an Er;

Yb predoped laser.

4. The apparatus of claim 1 further comprising:

the pre-seed laser comprising a continuous wave laser.

5. The apparatus of claim 1 further comprising:

the pre-seed laser comprising a pulsed laser.

6. The apparatus of claim 1 further comprising:

the amplifier laser comprising a pulse amplifier laser.

7. The apparatus of claim 1 further comprising:

the solid state seed laser system is tunable in nominal center wavelength and/or has a plurality of nominal center wavelength operating points.

8. The apparatus of claim 1 further comprising:

the frequency converter comprises a single or multiple non-linear frequency conversion stage.

9. The apparatus of claim 1 further comprising:

the amplifier gain medium is selected from the group comprising;

XeF, XeCl, KrF, ArF and F₂ gas discharge lasers.

10. The apparatus of claim 1 further comprising:

a coherence busting mechanism sufficiently destroying the coherence of the output of the seed laser system or the outputs of the amplifier gain mediums or both to reduce speckle effects in a processing tool using the light from the laser light source.

11. The apparatus of claim 10 further comprising:

the coherence busting mechanism comprising;

a first axis coherence busing mechanism and a second axis coherence busing mechanism.

12. The apparatus of claim 10 further comprising:

the coherence busting mechanism comprising a beam sweeping mechanism.

13. The apparatus of claim 12 further comprising:

the beam sweeping mechanism being driven in one axis by a first time varying actuation signal.

14. The apparatus of claim 13 further comprising:

the first actuation signal comprising a ramp signal and the second actuation signal comprising a sinusoid.

15. The apparatus of claim 13 further comprising:

the time varying signal has a frequency such that at least one fall cycle occurs within the time duration of a seed laser output pulse.

16. The apparatus of claim 1 further comprising:

a coherence busting mechanism comprising an optical delay path with misaligned optics.

17. The apparatus of claim 1 further comprising:

a coherence busting mechanism comprising an optical delay path longer than the coherence length of the seed laser output pulse and a beam pointing angle offset mechanism.

18. The apparatus of claim 1 further comprising:

a coherence busting mechanism comprising an active optical coherence busting mechanism and a passive optical coherence busting mechanism.

19. The apparatus of claim 18 further comprising:

the active coherence busting mechanism comprising a beam sweeping device and the passive coherence busting mechanism comprising an optical delay path.

20. The apparatus of claim 1 further comprising:

the coherence busting mechanism comprising;

a first optical delay path with a delay longer than the coherence length of the seed laser output pulse and a second optical delay path in series with the first optical delay path and having a delay path longer than the coherence length of the seed laser output pulse and different from the delay path of the first optical delay path;

a beam angular offset mechanism.

21. The apparatus of claim 20 further comprising:

the delay of the second optical delay path is greater than the delay path of the first optical delay path.

22. The apparatus of claim 1 further comprising:

a coherence busting mechanism comprising a beam flipping mechanism.

23. The apparatus of claim 1 wherein each of the first and second gas discharge laser amplifier gain mediums are part of a regenerative ring amplification stage.

24. An apparatus comprising:

a very high power broad band lithography laser light source comprising;

a solid state seed laser system comprising;

a pre-seed laser providing a pre-seed laser output;

a fiber amplifier receiving the pre-seed laser output and providing

an amplified seed laser pulse comprising;

a nominal wavelength outside of the DUV range;

a frequency converter modifying the nominal center wavelength of the output of the seed laser system to essentially the nominal center wavelength of the amplifier gain medium;

a first and a second gas discharge laser amplifier gain medium each operating at one half of the pulse repetition rate of the seed laser output;

a beam divider providing each respective first and second amplifier gain medium with alternating output pulses from the seed laser;

a beam combiner combining the outputs of each respective amplifier gain medium to provide a light source laser output light pulse beam having the pulse repetition rate of the solid state seed laser.

25. The apparatus of claim 24 wherein each of the first and second gas discharge laser amplifier gain mediums are part of a regenerative ring amplification stage.

26. An apparatus comprising:

a lithography laser light source comprising;

a solid state seed laser system comprising a CW solid state laser that is externally modulated and is amplified by a fiber amplifier;

a first and a second gas discharge laser amplifier gain medium each operating at a different pulse repetition rate than the pulse repetition rate of the seed laser output;

a beam divider providing each respective first and second amplifier gain medium with output pulses from the seed laser;

a frequency converter modifying the nominal center wavelength of the output of the seed laser system to essentially the nominal center wavelength of the amplifier gain medium;

a beam combiner combining the outputs of each respective amplifier gain medium to provide a laser output light pulse beam having the pulse repetition rate of the solid state seed laser.

27. The apparatus of claim 26 further comprising a coherence busting mechanism sufficiently destroying the coherence of the output of the seed laser system or the outputs of the gas discharge regenerative ring amplification stages or both to reduce speckle effects in a processing tool using the light from the laser light source.

28. The apparatus of claim 26 wherein each of the first and second gas discharge laser amplifier gain mediums are part of a regenerative ring amplification stage.

29. The apparatus of claim 26 wherein the fiber amplifier includes a large-mode area fiber.

30. An apparatus comprising:

a lithography laser light source comprising;

a fiber laser oscillator producing a seed pulse that is externally modulated and amplified by a fiber amplifier;

a first and a second gas discharge laser amplifier gain medium each operating at a different pulse repetition rate than the pulse repetition rate of the fiber laser oscillator output;

a beam divider providing each respective first and second amplifier gain medium with output pulses from the seed laser;

a frequency converter modifying the nominal center wavelength of the output of the fiber laser oscillator to essentially the nominal center wavelength of the amplifier gain medium; and

a beam combiner combining the outputs of each respective amplifier gain medium to provide a laser output light pulse beam having the pulse repetition rate of the fiber laser oscillator.