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

• US 20040009618A1
• Filed: 03/26/2003
• Published: 01/15/2004
• Est. Priority Date: 03/27/2002
• Status: Active Grant

• Current Assignee: Electro Scientific Industries Incorporated (MKS Instruments Incorporated)
• Original Assignee: GSI Group Corporation (Novanta Inc.)
• Inventors: Ehrmann, Jonathan S., Chu, Yun Fee, Johnson, Shepard D., Lento, Joseph V., Couch, Bruce L.
• Granted Patent: US 6,951,995 B2
• Time in Patent Office: Days
• US Class Current: 438/13
• 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 method for high-speed, precise micromachining an array of devices, each of the devices having at least one measurable property, the method comprising the steps of:

selectively micromachining a device in the array to vary a value of a measurable property;

suspending the step of selectively micromachining;

while the step of selectively micromachining is suspended, selectively micromachining at least one other device in the array to vary a value of a measurable property; and

resuming the suspended step of selectively micromachining to vary a measurable property of the device until its value is within a desired range.

2. The method of claim 1 wherein the devices are resistors.

3. The method of claim 2 wherein the resistors are film resistors.

4. The method of claim 1 wherein the steps of selectively micromachining are performed with at least one laser beam which cuts the devices.

5. The method of claim 1 further comprising measuring one measurable property of at least one of the devices to obtain a measured value.

6. The method of claim 5 further comprising comparing the measured value with a predetermined threshold to obtain a comparison and micromachining at least one of the other devices based on the comparison.

7. The method of claim 5 further comprising selectively micromachining at least one of the other devices based on the measured value.

8. The method of claim 5 further comprising determining not to measure a measurable property of at least one of the other devices based on the measured value.

9. The method of claim 1 wherein the method is for high-speed, precise laser trimming an array of resistors and wherein one of the measurable properties is resistance.

10. The method of claim 1 wherein each of the steps of selectively micromachining includes the step of selectively removing material.

11. The method of claim 1 wherein the array includes at least one of one or more rows and one or more columns.

12. The method of claim 1 wherein at least one of the steps of selectively micromachining is performed with a plurality of focused laser pulses to irradiate a plurality of devices substantially simultaneously.

13. The method of claim 1 wherein at least one of the steps of selectively micromachining is performed with a plurality of focused laser pulses and wherein the method further comprises distributing the focused laser pulses.

14. The method of claim 13 wherein the step of distributing includes the steps of producing a distribution pattern with a plurality of laser beams and focusing the laser beams.

15. The method of claim 9 wherein the laser trimming produces a series of interdigited cuts in an area of resistive material between conductors of the resistors.

16. The method of claim 1 wherein at least one of the steps of selectively micromachining includes the steps of positioning a laser beam at a location of each of the devices to be micromachined and selectively irradiating at least a portion of each of the devices to be micromachined with at least one laser pulse.

17. The method of claim 1 wherein at least one of the steps of selectively micromachining includes the steps of generating and relatively positioning a laser beam to travel in a first direction within a field of the array and selectively irradiating at least a portion of at least one device within the field with at least one laser pulse.

18. The method of claim 17 further comprising generating and relatively positioning a laser beam to travel in a second direction substantially opposite the first direction within the field and selectively irradiating at least a second portion of at least one device within the field with at least one laser pulse.

19. The method of claim 1 wherein at least one of the steps of selectively micromachining includes the steps of generating and relatively positioning a laser beam to travel in a first scanning pattern across the devices, superimposing a second scanning pattern with the first scanning pattern and irradiating at least one device with at least one laser pulse.

20. The method of claim 19 wherein the second scanning pattern is a retrograde scan and wherein scan speed of the at least one laser pulse irradiating the at least one device is lower than a corresponding scan speed of the first scanning pattern wherein laser energy is concentrated at the at least one device for a period of time longer than a period of time associated with only the first scanning pattern whereby throughput is improved.

21. The method of claim 19 wherein the second scanning pattern includes a jump from a first device to a second device.

22. The method of claim 1 wherein the steps of selectively micromachining are performed with a plurality of laser pulses and wherein at least one of the pulses has an energy in the range of 0.1 microjoules to 25 millijoules.

23. The method of claim 7 wherein the measured value is a measured temperature value.

24. The method of claim 1 wherein the devices are substantially identical.

25. A system for high-speed, laser-based, precise micromachining an array of devices, each of the devices having at least one measurable property, the system comprising:

a pulsed laser subsystem;

an optical subsystem coupled to the pulsed laser system to selectively irradiate a portion of a device with a laser pulse; and

a controller coupled to the subsystems to control the subsystems to;

selectively micromachine a device in the array to vary a value of a measurable property;

suspend the selective micromachining;

while the selective micromachining is suspended, selectively micromachine at least one other device in the array to vary a value of a measurable property; and

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

26. The system of claim 25 wherein the optical subsystem includes a beam deflector and a beam deflector controller for controlling the beam deflector to scan a laser beam along a first scan pattern which includes each of the devices to be micromachined.

27. The system of claim 25 further comprising a measurement subsystem to measure one of the measurable properties of at least one of the devices.

28. The system of claim 27 wherein the micromachining is laser trimming and the array is an array of resistors and wherein the measurement subsystem is a probe array.

29. The system of claim 26 wherein the optical subsystem includes a second beam deflector to superimpose a higher-speed, second scan pattern on the first scan pattern whereby throughput of the system is improved.

30. The system of claim 25 wherein the controller is coupled to the subsystems so that the subsystems are controlled to generate a trimming sequence for at least one of the devices that reduces device temperature during micromachining.