Femtosecond laser processing system with process parameters, controls and feedback

• US 8,279,903 B2
• Filed: 02/11/2011
• Issued: 10/02/2012
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Bovatsek, James M., Arai, Alan Y., Yamamoto, Tadashi, Patel, Rajesh S., Harter, Donald J., Shah, Lawrence
• Primary Examiner(s): NGUYEN, DUNG T
• Application Number:
  US13/025,408
• Publication Number:
  US 20110139760A1
• Time in Patent Office: 599 Days
• Field of Search: 372/20, 372/25, 372/30
• US Class Current: 372/30
• 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. A method of laser-based device fabrication, comprising:

irradiating a target material with ultrashort laser pulses;

monitoring a pulse characteristic of the ultrashort pulses, and a condition of the target material, to obtain process information, wherein said pulse characteristic comprises at least one of an average output power, a pulse width, wavelength, repetition rate, polarization, temporal delay, temporal phase and spatial phase;

modifying the pulse characteristic based on the process information, wherein the monitoring and modifying are carried out using ultrashort laser pulses directed downstream toward a material processing beam path for application to target material; and

irradiating the target material with at least one ultrashort laser pulse having a modified pulse characteristic based on said process information, so as to modify said target material, wherein said method of device fabrication comprises active control of a laser-material interaction during fabrication of said device.

2. The method as claimed in claim 1, wherein the ultrashort pulses comprise at least one pulse having a pulse width in the range of about 10 fs to 1 ps.

3. The method as claimed in claim 1, wherein the device is configured for a microelectronic application, and the target substrate comprises silicon.

4. The method as claimed in claim 1, wherein said target material is transparent at a laser wavelength, said fabrication comprises laser welding of said transparent material at said wavelength, and said step of irradiating comprises applying high repetition rate femtosecond laser pulses generated at a repetition rate in the range from 10 kHz to 50 MHz so as to allow for accumulation of heat from pulse-to-pulse.

5. The method as claimed in claim 1, wherein said method comprises annealing an amorphous substrate material into a polycrystalline form and, during said step of irradiating with ultrashort laser pulses, a reduced substrate temperature is maintainable relative to a 300-400 degree Celsius range utilized with excimer laser-based annealing.

6. The method as claimed in claim 5, wherein said reduced substrate temperature is about 200 degrees Celsius.

7. The method as claimed in claim 1, wherein said monitoring a condition of the target material comprises spectroscopic analysis of light generated during laser ablation, said step of modifying a pulse characteristic being performed based on a result obtained from said analysis.

8. The method as claimed in claim 1, wherein said method comprises controlled deposition of a film, and at least a portion of said ultrashort pulses are in an ultraviolet wavelength range.

9. The method as claimed in claim 1, wherein said laser pulses are generated with a chirped pulse amplification system.

10. The method as claimed in claim 1, wherein said irradiating based on said process information controls the quantity of energy and the size and/or shape of the irradiated volume, wherein a three-dimensional structure is formed in a single pass.

11. The method as claimed in claim 10, wherein said three-dimensional structure is tapered or periodic.

12. The method as claimed in claim 1, wherein said method comprises forming one or more of a hole, channel, trench, groove, and via in the target material.

13. The method as claimed in claim 1, wherein said method comprises micro-marking said material to form a pattern on or within said material.

14. The method as claimed in claim 1, wherein said method comprises modifying a refractive index of said material.

15. The method of claim 1, further comprising:

generating the ultrashort pulses with an ultrashort pulsed source capable of generating the ultrashort pulses at a variable repetition rate in the range from 10 kHz to 50 MHz .

16. The method of claim 1, wherein the target material is transparent at a wavelength of said laser pulses.

17. The method of claim 1, wherein said method further comprises generating ultrashort pulses with a fiber-based laser system, wherein said fiber-based system includes zero, one, or more fiber amplifiers.

18. A method of laser-based device fabrication, comprising:

irradiating a target material with ultrashort laser pulses;

monitoring a pulse characteristic of the ultrashort pulses, and a condition of the target material, to obtain process information;

modifying the pulse characteristic based on the process information; and

irradiating the target material with at least one ultrashort laser pulse having a modified pulse characteristic based on said process information, so as to modify said target material, wherein said method of device fabrication comprises active control of a laser-material interaction during fabrication of said device,

wherein said method comprises writing a line on or within the target material at a repetition rate greater than about 10 kHz, said line having a linewidth substantially smaller than a spot diameter of a focused ultrashort pulse.

19. The method as claimed in claim 18, wherein said linewidth is about 15 nm.

20. A method of laser-based device fabrication, comprising:

irradiating a target material with ultrashort laser pulses, wherein at least a portion of said ultrashort pulses comprise two or more pulses overlapped in time, and the time between the pulses is varied, at least one pulse having a pulse width in the range from about 10 femtoseconds to 1 picosecond;

monitoring a pulse characteristic of the ultrashort pulses, and a condition of the target material, to obtain process information;

modifying the pulse characteristic based on the process information; and

irradiating the target material with at least one ultrashort laser pulse having a modified pulse characteristic based on said process information, so as to modify said target material, wherein said method of device fabrication comprises active control of a laser-material interaction during fabrication of said device.

21. A system for laser-based device fabrication, comprising:

a fiber-based source of ultrashort pulses capable of generating output pulses at a varying repetition rate in the range from 10 kHz to 50 MHz, the output pulses being directed downstream toward a material processing beam path for application to target material;

means for irradiating a target material with ultrashort laser pulses;

means for monitoring a pulse characteristic of the ultrashort pulses, and a condition of the target material, to obtain process information, wherein said pulse characteristic comprises at least one of an average output power, a pulse width, a wavelength, a repetition rate, a polarization, a temporal delay, a temporal phase and a spatial phase; and

means for modifying the pulse characteristic based on the process information, wherein said means for irradiating, monitoring, and modifying, in combination, provides active control of a laser-material interaction during device fabrication, wherein said system is configured such that an operation of each of said means is individually or cooperatively adjustable based on at least one of a device characteristic and said process information.

22. The system of claim 21, wherein the means for monitoring and the means for modifying are connected to a control means that generates control signals in response to pulse characteristics of the ultrashort pulses.

23. The system of claim 21, wherein the means for irradiating comprises beam steering optics to control an impingement location of the laser pulses on the target material.

24. The system of claim 21, wherein a device, which is fabricated by the device fabrication, comprises a substrate, and the device characteristic comprises a substrate temperature or a position of said substrate.

25. The system of claim 21, wherein the device characteristic comprises a spectral characteristic.

26. The system of claim 21, wherein a device, which is fabricated by the device fabrication, comprises a chemical, biological, or medical device.

27. The system of claim 21, wherein a device, which is fabricated by the device fabrication, comprises a semiconductor material or a transparent material.

28. The system of claim 21, wherein operation of each of said means is individually or cooperatively adjustable with feedback loops and under computer control.

29. The system of claim 21, wherein the means for monitoring the condition of the target material comprises:

at least one of an illumination and a microscopic viewing system to examine a target substrate, spectroscopic diagnostics, a range finder and a camera based imaging system.

30. The system of claim 21, wherein said pulse characteristic comprises:

at least one of an average output power, a pulse width, wavelength, repetition rate, polarization, temporal delay, temporal phase and spatial phase.