Acousto-optic deflector applications in laser processing of dielectric or other materials

• US 10,391,585 B2
• Filed: 03/25/2013
• Issued: 08/27/2019
• Est. Priority Date: 05/28/2009
• Status: Active Grant

• Current Assignee: Electro Scientific Industries Incorporated (MKS Instruments Incorporated)
• Original Assignee: Electro Scientific Industries Incorporated (MKS Instruments Incorporated)
• Inventors: Unrath, Mark A., Jordens, William J., Ismail, James, Matsumoto, Hisashi, Lineburg, Brian J.
• Primary Examiner(s): Abraham, Ibrahime A
• Assistant Examiner(s): Bae, Gyounghyun
• Application Number:
  US13/850,168
• Publication Number:
  US 20130299468A1
• Time in Patent Office: 2,346 Days
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/046 Automatically focusing the laser beam
• CPC Class Codes: B23K 26/0648 comprising lenses
• CPC Class Codes: B23K 26/0665 by beam condensation on the workpiece, e.g. for focusing
• CPC Class Codes: B23K 26/08 Devices involving relative movement between laser beam and workpiece
• CPC Class Codes: B23K 26/082 Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved

Abstract

A laser processing system for micromachining a workpiece includes a laser source to generate laser pulses for processing a feature in a workpiece, a galvanometer-driven (galvo) subsystem to impart a first relative movement of a laser beam spot position along a processing trajectory with respect to the surface of the workpiece, and an acousto-optic deflector (AOD) subsystem to effectively widen a laser beam spot along a direction perpendicular to the processing trajectory. The AOD subsystem may include a combination of AODs and electro-optic deflectors. The AOD subsystem may vary an intensity profile of laser pulses as a function of deflection position along a dither direction to selectively shape the feature in the dither direction. The shaping may be used to intersect features on the workpiece. The AOD subsystem may also provide rastering, galvo error position correction, power modulation, and/or through-the-lens viewing of and alignment to the workpiece.

Claims

1. A system comprising:

an acousto-optic deflector (AOD) subsystem including;

a first AOD arranged to receive a laser beam input to the AOD subsystem, wherein the first AOD is operative to generate an acoustic waveform therein sufficient to diffract the input laser beam in a first direction and thereby output a first diffracted laser beam when driven by a first radio frequency (RF) signal;

a second AOD arranged to receive the first diffracted beam, wherein the second AOD is operative to generate an acoustic waveform therein sufficient to diffract the first diffracted laser beam in a second direction perpendicular to the first direction when driven by a second RF signal and thereby output a second diffracted laser beam from the AOD subsystem;

a computer coupled to the first AOD and the second AOD and operative to execute machine-readable instructions to control an operation of the first AOD and the second AOD; and

a non-transitory machine-readable medium coupled to the computer, the machine-readable medium having instructions stored thereon which, when executed by the computer, cause at least one selected from the group consisting of the first AOD and the second AOD to generate therein a chirped acoustic waveform.

2. The system of claim 1, further comprising a positioner to impart a first relative movement of a laser beam spot position along a processing trajectory with respect to the surface of the workpiece.

3. The system of claim 2, wherein the positioner is selected from the group comprising a galvanometer-driven (galvo) subsystem and a fast-steering mirror (FSM) subsystem.

4. The system of claim 2, wherein

the computer is coupled to the positioner and is operative to execute machine-readable instructions to control an operation of the positioner, and

wherein the machine-readable medium has instructions stored thereon which, when executed by the computer, cause the AOD subsystem to impart a second relative movement of the laser beam spot position along a direction perpendicular to the processing trajectory, wherein the second relative movement is superimposed on the first relative movement, and wherein the second relative movement is at a higher velocity than that of the first relative movement.

5. The system of claim 4, wherein the machine-readable medium has instructions stored thereon which, when executed by the computer, cause the AOD subsystem to vary an intensity profile of the laser beam as a function of deflection position along the direction perpendicular to the processing trajectory to thereby selectively shape the feature in the direction perpendicular to the processing trajectory.

6. The system of claim 5, wherein the machine-readable medium has instructions stored thereon which, when executed by the computer, cause the AOD subsystem to adjust the average fluence of the laser beam based on the laser beam spot position along the direction perpendicular to the processing trajectory.

7. The system of claim 6, wherein the machine-readable medium has instructions stored thereon which, when executed by the computer, cause the AOD subsystem to adjust the average fluence of a power amplitude of the laser beam based on deflection positions along the processing trajectory.

8. The system of claim 1, further comprising:

a shaping element for shaping an intensity profile of the laser beam; and

a relay lens positioned to receive the laser beam from the AOD subsystem and to center the laser beam on an aperture of the shaping element independent of a deflection angle provided by the AOD subsystem to the laser beam.

9. The system of claim 8, wherein the shaping element comprises a diffractive optical element.

10. The system of claim 1, further comprising a laser source operative to generate a laser beam, wherein an input of the acousto-optic deflector (AOD) subsystem is optically coupled to an optical output of the laser source.

11. The system of claim 10, wherein the laser source is a pulsed laser source.

12. The system of claim 1, further comprising a scan lens, wherein an output of the acousto-optic deflector (AOD) subsystem is optically coupled to the scan lens.

13. The system of claim 12, wherein the system does not include any AOD between the AOD subsystem and the scan lens.

14. The system of claim 12, further comprising:

a relay lens positioned to receive the laser beam output from the AOD subsystem at a selected location with respect to the scan lens such that an angle of incidence of the laser beam at the surface of the workpiece corresponds to an angle at which the laser beam is deflected by the AOD subsystem.

15. The system of claim 1, wherein the machine-readable medium has instructions stored thereon which, when executed by the computer, cause each of the first AOD and the second AOD to generate therein a chirped acoustic waveform.

16. The system of claim 1, wherein the AOD subsystem includes only two AODs.