Method and system for high-speed, precise micromachining an array of devices

• US 6,951,995 B2
• Filed: 03/26/2003
• Issued: 10/04/2005
• Est. Priority Date: 03/27/2002
• Status: Expired due to Fees

• Current Assignee: Electro Scientific Industries Incorporated (MKS Instruments Incorporated)
• Original Assignee: GSI Lumonics Corporation (Novanta Inc.)
• Inventors: Ehrmann, Jonathan S., Chu, Yun Fee, Johnson, Shepard D., Lento, Joseph V., Couch, Bruce L.
• Primary Examiner(s): GHYKA, ALEXANDER G
• Application Number:
  US10/397,541
• Publication Number:
  US 20040009618A1
• Time in Patent Office: 923 Days
• Field of Search: 219/121.67, 219/121.68, 438/13, 438/382
• US Class Current: 219/121.67
• CPC Class Codes: B23K 2101/38 Conductors
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 26/03 Observing, e.g. monitoring, the workpiece
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/034 Observing the temperature of the workpiece
• CPC Class Codes: B23K 26/04 Automatically aligning, aiming or focusing the laser beam, e.g. using the back-scattered light
• CPC Class Codes: B23K 26/0622 by shaping pulses
• CPC Class Codes: B23K 26/064 by means of optical elements, e.g. lenses, mirrors or prisms
• CPC Class Codes: B23K 26/0665 by beam condensation on the workpiece, e.g. for focusing
• CPC Class Codes: B23K 26/073 Shaping the laser spot
• CPC Class Codes: B23K 26/0736 into an oval shape, e.g. elliptic shape
• 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 26/0823 Devices involving rotation of the workpiece
• CPC Class Codes: B23K 26/0853 Devices involving movement of the workpiece in at least in two axial directions, e.g. in a plane
• CPC Class Codes: B23K 26/351 for trimming or tuning of electrical components
• CPC Class Codes: B23K 26/361 for deburring or mechanical trimming B23K26/351 takes precedence
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: H01C 17/242 by laser trimming by laser in general B23K26/351
• CPC Class Codes: H01L 27/016 Thin-film circuits
• CPC Class Codes: H01L 28/20 Resistors

Abstract

A method and system for high-speed, precise micromachining an array of devices are disclosed wherein improved process throughput and accuracy, such as resistor trimming accuracy, are provided. The number of resistance measurements are limited by using non-measurement cuts, using non-sequential collinear cutting, using spot fan-out parallel cutting, and using a retrograde scanning technique for faster collinear cuts. Non-sequential cutting is also used to manage thermal effects and calibrated cuts are used for improved accuracy. Test voltage is controlled to avoid resistor damage.

Claims

1. A system for high-speed, laser-based, precise laser trimming at least one electrical element having at least one measurable property, the at least one element being supported on a substrate, the system comprising:

a laser subsystem to generate a pulsed laser output having one or more laser pulses at a repetition rate, each laser pulse having a pulse energy, a visible laser wavelength, and a pulse duration;

a beam delivery subsystem that accepts the pulsed laser output and includes;

at least one beam deflector to position the one or more laser pulses relative to the at least one element to be trimmed; and

an optical subsystem to focus the one or more laser pulses having the visible laser wavelength into at least one spot within a field of the optical subsystem;

the at least one spot having a non-uniform intensity profile along a direction and a spot diameter as small as about 6 microns to about 15 microns; and

a controller coupled to the beam delivery and laser subsystems to control the beam delivery and laser subsystems to selectively irradiate the at least one element such that the one or more laser output pulses having the visible laser wavelength, the pulse duration, the pulse energy and the spot diameter selectively remove material from the at least one element and laser trim the at least one element while avoiding substantial microcracking within the at least one element.

2. The system of claim 1, wherein the spot is substantially diffraction limited, and wherein the non-uniform intensity profile is approximately a Gaussian profile along the direction.

3. The system of claim 1, wherein substantial microcracking is also avoided within material proximal to the at least one element.

4. The system of claim 1, wherein the laser subsystem includes a q-switched, frequency-doubled, diode-pumped, solid state laser.

5. The system of claim 1, wherein the laser subsystem includes a q-switched, frequency-doubled, solid state laser having a fundamental wavelength in the range of about 1.047 microns to 1.32 microns, and the visible output wavelength is a frequency-doubled wavelength in a visible wavelength range of about 0.5 microns to about 0.7 microns.

6. The system of claim 1, wherein the laser wavelength is a green laser wavelength.

7. The system of claim 6, wherein the green laser wavelength is about 532 nm.

8. The system of claim 1, wherein the spot diameter is as small as about 6 microns to about 10 microns.

9. The system of claim 1, wherein the optical subsystem includes a lens that is achromatized at two or more wavelengths, at least one of the wavelengths being a visible wavelength.

10. The system of claim 9, further comprising:

an illuminator to illuminate a substrate region with radiant energy at one or more illumination wavelengths; and

a detection device having sensitivity to the radiant energy at one of the illumination wavelengths wherein one of the two or more wavelengths is a visible laser wavelength and the other is the illumination wavelength.

11. The system of claim 1, wherein the optical subsystem is a telecentric optical subsystem.

12. The system of claim 11, wherein the telocentric optic subsystem includes a telecentric lens.

13. The system of claim 1, wherein the repetition rate is at least 10 Kilohertz.

14. The system of claim 1, wherein the pulse duration of at least one laser pulse of the laser output is in the range of about 25 nanoseconds to about 45 nanoseconds.

15. The system of claim 1, wherein the pulse duration of at least one laser pulse of the laser output is less than about 30 nanoseconds.

16. The system of claim 1, wherein the controller includes means for controlling position of the pulsed laser output relative to the at least one element.

17. The system of claim 1, wherein the controller includes means for controlling the pulse energy to selectively irradiate the at least one element.

18. The system of claim 1, further comprising a substrate positioner to position the at least one element supported on the substrate relative to and within the field of the optical subsystem such that the one or more laser pulses are focused and irradiate the at least one element with a spot diameter as small as about 6 microns to about 15 microns.

19. The system of claim 1, wherein the optical subsystem receives the at least one laser pulse subsequent to deflection by the at least one beam deflector.

20. The system of claim 18, wherein the focused spot diameter is as small as about 6 microns to about 10 microns at any location within the field of the optical subsystem.

21. The system of claim 1, further comprising a calibration algorithm to adjust coordinates of material to be irradiated within the at least one element and to thereby precisely control a dimension of a region of material removal.

22. The system of claim 1, further comprising a machine vision subsystem including a vision algorithm to locate or measure at least one geometric feature of the at least one element.

23. The system of claim 22, wherein the vision algorithm includes edge detection and the at least one geometric feature are edges of the at least one element, the edges being used to determine width of the at least one element and to define a dimension for material removal.

24. The system of claim 1, wherein the at least one element includes a thin-film resistor, and wherein the at least one measurable property is at least one of resistance and temperature, and wherein the system further includes means for suspending removal of thin film material of the resistor when a measurement of at least one measurable property is within a predetermined range.

25. The system of claim 1, wherein a material of the substrate is a semiconductor.

26. The system of claim 1, wherein a material of the substrate is a ceramic.

27. The system of claim 1, wherein the at least one element includes a thin-film element.

28. The system of claim 1, wherein an array of thin-film electrical elements is to be trimmed with the system and wherein the controller includes:

means to selectively micromachine an array element to vary a value of a measurable property;

means to suspend the selective micromachining while the selective micromachining is suspended;

means to selectively micromachine at least one other array element to vary a value of a measurable property; and

means to resume the selective micromachining to vary a measurable property of the array element until its value is within a desired range.

29. The system of claim 1, further comprising a user interface, and a software program coupled to the interface and the controller, the software program adapted to accept pre-trim target values for the at least one element and to limit an electrical output being applied to the at least one element based on the values.

30. The system of claim 29, wherein potential damage to the at least one element is avoided.