Femtosecond laser processing system with process parameters, controls and feedback

• US 7,912,100 B2
• Filed: 12/19/2008
• Issued: 03/22/2011
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Patel, Rajesh S., Bovatsek, James M., Yamamoto, Tadashi, Harter, Donald J., Arai, Alan Y., Shah, Lawrence
• Primary Examiner(s): Nguyen; Dung T
• Application Number:
  US12/339,744
• Publication Number:
  US 20090097514A1
• Time in Patent Office: 823 Days
• Field of Search: 372/6, 372/9, 372/25, 372/30
• US Class Current: 372/6
• CPC Class Codes: G01J 11/00 Measuring the characteristics of individual optical pulses or of optical pulse trains
• CPC Class Codes: H01S 3/0014 Monitoring arrangements not otherwise provided for photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003
• 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 3/0064 Anti-reflection devices, e.g. optical isolaters absorbing layers for marking or protecting purposes in laser working B23K26/50; magneto-optical non-reciprocal devices G02F1/093, G02F1/0955
• CPC Class Codes: H01S 3/0078 Frequency filtering
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/10023 by functional association of additional optical elements, e.g. filters, gratings, reflectors
• CPC Class Codes: H01S 3/10038 Amplitude control
• CPC Class Codes: H01S 3/10061 Polarization control
• CPC Class Codes: H01S 3/102 by controlling the active medium, e.g. by controlling the processes or apparatus for excitation H01S3/13 takes precedence
• CPC Class Codes: H01S 3/1024 for pulse generation
• CPC Class Codes: H01S 3/108 using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering mode locking using a non-linear element H01S3/1112
• CPC Class Codes: H01S 3/109 Frequency multiplication, e.g. harmonic generation
• CPC Class Codes: H01S 3/1305 Feedback control systems
• CPC Class Codes: H01S 3/1618 ytterbium

Abstract

A femtosecond laser based laser processing system having a femtosecond laser, frequency conversion optics, beam manipulation optics, target motion control, processing chamber, diagnostic systems and system control modules. The femtosecond laser based laser processing system allows for the utilization of the unique heat control in micromachining, and the system has greater output beam stability, continuously variable repetition rate and unique temporal beam shaping capabilities.

Claims

1. An apparatus for impinging laser pulses on a target substrate, the apparatus comprising:

laser means for generating bursts of pulses, said laser means comprising a femtosecond pulse source having a fiber gain medium;

control means that controls the laser means; and

beam manipulation means for monitoring characteristics of the bursts output from the laser means to generate feedback data for the control means, and for manipulating the characteristics of the bursts, said beam manipulation means comprising steering optics that control the impingement location of the laser pulses on the target, said apparatus comprising one or more of a range finder, viewing, and spectroscopic tool to monitor a condition of said target substrate; and

means for positioning the target substrate.

2. The apparatus as claimed in claim 1, wherein the beam manipulation means comprising:

a power meter that measures the power of the laser pulses output from the laser means;

a photodiode that measures the repetition rate of the laser pulses; and

an optical gating device that measures the pulse duration of the laser pulses.

3. The apparatus as claimed in claim 1, wherein the beam manipulation means comprise means for optically converting the fundamental frequency of a percentage of the generated laser pulses to one or more other optical frequencies.

4. The apparatus as claimed in claim 3, the means for converting an optical frequency comprising at least one optical member that converts a portion of the fundamental frequency of the laser pulses into at least one higher order harmonic signal.

5. The apparatus as claimed in claim 4, wherein the optical member device comprises at least one non-linear crystal device.

6. The apparatus as claimed in claim 5, wherein the non-linear crystal device further comprises a controller that controls the orientation of the at least one non -linear crystal with respect to the input laser pulses.

7. The apparatus as claimed in claim 5, wherein the non-linear crystal device further comprises a dual-lens telescope that focuses the input laser pulses into the at least one non-linear crystal, wherein the at least one non-linear crystal is disposed between the lenses of the telescope.

8. The apparatus as claimed in claim 7, wherein the dual-lens telescope collimates the output of the at least one non-linear crystal.

9. The apparatus as claimed in claim 4, wherein the means for converting an optical frequency further comprise a spectrometer that measures predetermined parameters of pulses output from the non-linear crystal device.

10. The apparatus as claimed in claim 1, wherein the beam manipulation means comprises:

a telescopic optical device to control the size, shape, divergence or polarization of the laser pulses input into the means for manipulating.

11. The apparatus as claimed in claim 10, the apparatus further comprising:

a beam profiler that monitors characteristics of laser pulses output from the telescopic optical device; and

a position detector that determines a position of the laser pulses output from the steering optics.

12. The apparatus as claimed in claim 10, wherein the telescopic optical device comprises at least two cylindrical lens telescopes aligned along an optical axis traversed by the laser pulses.

13. The apparatus as claimed in claim 3, wherein the apparatus further comprises:

means for directing the fundamental and/or converted frequencies of the laser pulses and the impingement location of the pulses with respect to the target substrate;

means for focusing the fundamental and/or converted frequencies of the laser pulses.

14. The apparatus as claimed in claim 1, the means for positioning comprising:

a mounting surface for translating the target with respect to the laser pulses; and

a motion control device coupled to the mounting surface.

15. The apparatus as claimed in claim 14, the means for positioning further comprising an environmental chamber, wherein the mounting surface and the motion control device are disposed within the environmental chamber.

16. The apparatus as claimed in claim 1, wherein said apparatus is configured for modifying the refractive index of a target substrate.

17. The apparatus as claimed in claim 1, wherein said apparatus is configured for surface marking, sub-surface marking and surface texturing of a target substrate.

18. The apparatus as claimed in claim 1, wherein said apparatus is configured for fabricating holes, channels or vias in a target substrate.

19. The apparatus as claimed in claim 1, wherein said apparatus is configured for the deposition or removal of thin layers of material on a target substrate.

20. The apparatus as claimed in claim 1, wherein said apparatus is configured for the joining, welding or fusing of transparent materials.

23. The apparatus as claimed in claim 1, wherein said apparatus is configured to include laser induced breakdown spectroscopy (LIBS).

24. The apparatus as claimed in claim 1, wherein said apparatus is configured for surface or sub-surface material modification of said target substrate.

25. The apparatus as claimed in claim 1, wherein said femtosecond pulse source comprises a fiber laser.

21. An apparatus as claimed in 1, wherein the laser means comprises a fiber amplifier.

22. An apparatus as claimed in claim 21, wherein the laser means further comprise at least one stretcher and at least one grating compressor.

26. An apparatus for impinging pulses on a target substrate, the apparatus comprising:

laser means for generating optical pulses, and for amplifying said pulses in a same fiber amplifier gain medium, wherein said laser means is configured so that each of said pulses are incident on said same fiber laser gain medium and emitted from the same fiber gain medium along a common optical path;

control means that controls the laser means; and

beam manipulation means for monitoring a characteristic of said optical pulses, and for monitoring said target substrate, said beam manipulation means being operable to generate feedback data for the control means based on target and pulse information, the beam manipulating means comprising;

a telescopic optical device to control the size, shape, divergence or polarization of the laser pulses input into the beam manipulation means, and steering optics that control an impingement location of the laser pulses on the target substrate;

means for positioning the target substrate.

27. The apparatus as claimed in claim 26, wherein said apparatus is configured to include laser induced breakdown spectroscopy (LIBS).

28. The apparatus as claimed in claim 26, wherein said apparatus is configured for surface or sub-surface material modification of said target substrate.

29. An apparatus for impinging pulses on a target substrate, the apparatus comprising:

laser means for generating optical pulses having pulse widths in the range of femtoseconds to picoseconds, said laser means comprising a fiber gain medium;

control means that controls the laser means;

beam manipulation means for monitoring a characteristic of said optical pulses, and for monitoring said target substrate, said beam manipulation means being operable to generate feedback data for the control means based on target and pulse information, said beam manipulation means comprising steering optics that control an impingement location of the laser pulses on the target substrate, said apparatus comprising one or more of a range finder, viewing, and spectroscopic tool to monitor a condition of said target substrate; and

means for positioning the target substrate.

30. The apparatus as claimed in claim 29, wherein said laser means comprises a fiber amplifier for amplifying said pulses in a same fiber amplifier gain medium, and wherein said laser means is configured so that each of said pulses are incident on said same fiber laser gain medium and emitted from the same fiber gain medium along a common optical path.

31. The apparatus as claimed in claim 29, wherein the beam manipulating means comprises:

a telescopic optical device to control the size, shape, divergence or polarization of the laser pulses input into the beam manipulation means.

32. The apparatus as claimed in claim 29, wherein said laser means comprises an amplified ultrashort fiber laser system producing output pulses having at least one pulse width in the range of about 10 fs to 1 ps.

33. The apparatus as claimed in claim 29, wherein said optical pulses comprise pulses forming a burst.

34. The apparatus as claimed in claim 29, wherein a pulse characteristic being monitored comprises at least one of time separation, pulse width, peak power, different wavelength, and polarization.

35. The apparatus as claimed in claim 29, wherein said beam manipulation means produces a beam at a fundamental frequency, at least one harmonic beam at a multiple of said fundamental frequency, and is configured to transmit information for diagnostics from said beam manipulation means to said control means.

36. The apparatus as claimed in claim 29, wherein said apparatus is configured for modifying the refractive index of a target substrate.

37. The apparatus as claimed in claim 29, wherein said apparatus is configured for surface marking, sub-surface marking and surface texturing of a target substrate.

38. The apparatus as claimed in claim 29, wherein said apparatus is configured for fabricating holes, channels or vias in a target substrate.

39. The apparatus as claimed in claim 38, wherein said target substrate comprises a semiconductor substrate.

40. The apparatus as claimed in claim 29, wherein said apparatus is configured for the deposition or removal of thin layers of material on a target substrate.

41. The apparatus as claimed in claim 29, wherein said apparatus is configured for the joining, welding or fusing of transparent materials.

42. The apparatus as claimed in claim 29, wherein said apparatus is configured to include laser induced breakdown spectroscopy (LIBS).

43. The apparatus as claimed in claim 29, wherein said apparatus is configured for surface or sub-surface material modification of said target substrate.

44. The apparatus as claimed in claim 29, wherein said laser means comprises a fiber laser.

45. The apparatus of claim 38, wherein said target substrate comprises a material transparent at a laser wavelength of said laser means.

46. The apparatus of claim 38, wherein a thin film, conductive layer of ITO, an insulative layer of low-K dielectric, and/or chemical resistance layer of ZrO₂ is disposed on said substrate.

47. An apparatus for impinging laser pulses on a target substrate, the apparatus comprising:

laser means for generating bursts of pulses;

control means that controls the laser means;

beam manipulation means for monitoring characteristics of the pulse bursts output from the laser means to generate feedback data for the control means, and for manipulating the characteristics of the pulse bursts, the beam manipulation means comprising;

a power meter that measures the power of the laser pulses output from the laser means;

a photodiode that measures the repetition rate of the laser pulses; and

an optical gating device that measures the pulse duration of the laser pulses; and

means for positioning the target substrate.

48. The apparatus of claim 47, wherein said laser means comprises a fiber laser.

49. The apparatus of claim 47, wherein said apparatus is configured to include laser induced breakdown spectroscopy (LIBS).