Inspection system for micromechanical devices

• US 6,088,474 A
• Filed: 07/23/1997
• Issued: 07/11/2000
• Est. Priority Date: 07/23/1997
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Russell, Donald E., Barker, Paul G., Leonard, Anthony S., Streckmann, George L., Dudasko, David V., Doane, Dennis L.
• Primary Examiner(s): Mancuso, Joseph
• Assistant Examiner(s): COOPERRIDER, FRED E
• Application Number:
  US08/899,127
• Time in Patent Office: 1,084 Days
• Field of Search: 382/141, 382/149, 382/145, 364/468.17, 364/428.28, 324/522, 324/118, 324/751, 324/770, 348/92, 348/93, 348/125, 348/126, 348/128, 348/133, 348/134, 437/227, 257/415
• US Class Current: 382/145
• CPC Class Codes: B81C 99/004 during manufacturing
• CPC Class Codes: B81C 99/005 Test apparatus

Abstract

A visual inspection system (10) and method for inspecting the operation of micromechanical devices. The system has a vision system (16), a vision system controller (18), a system controller (20), an illumination system (12), a digital signal processor and a mounting stage (22). The objects undergoing inspection, either wafers or devices, are mounted under the visions system. A probe card is engaged to the object and power is provided. The vision system (16) records which elements or devices on the object begin operating at that voltage. The voltage is then incremented and the process continues until a determination is made as to the objects operability. The system can also be adapted to inspect micromechanical spatial light modulators by generating images with the modulator and capturing them with the image system. The digital signal processor then analyzes the images while the vision system moves to the next object to be inspected.

Claims

1. A method for inspecting micromechanical devices, comprising the steps of:

(a) providing a semiconductor device containing movable micromechanical elements as a part thereof which are movable in response to predetermined voltages applied to said semiconductor device;

(b) selecting a first micromechanical element of said micromechanical elements in a first region on said device for inspection;

(c) sending a first predetermined voltage to said first micromechanical element to provide said micromechanical element with power;

(d) capturing an image of the response of said first micromechanical element to said first predetermined voltage;

(e) optically analyzing said image to determine if said micromechanical element is operational at said first predetermined voltage;

(f) incrementing said voltage to a second predetermined voltage different from said first predetermined voltage;

(g) repeating said steps of sending, capturing and optically analyzing; and

(h) selecting a second micromechanical element in a second region on said device and repeating all of said steps (c) through (g) on said second micromechanical element until a characterization of electrical operation of each of said micromechanical elements has been produced.

2. The method of claim 1, wherein said micromechanical device is a wafer.

3. The method of claim 1, wherein said micromechanical device is a micromechanical spatial light modulator.

9. The method of claim 1 wherein said step of optically analyzing includes the steps of optically analyzing includes the steps of shining a reflectable light on the object, receiving light reflected from the object and determining the degree of reflection of the light from the object.

10. The method of claim 2 wherein said step of optically analyzing includes the steps of shining a reflectable light on said object, receiving light reflected from said object and determining the degree of reflection of said light from said object.

11. The method of claim 3 wherein said step of optically analyzing includes the steps of shining a reflectable light on said object, receiving light reflected from said object and determining the degree of reflection of said light from said object.

12. The method of claim 1 further including the steps of engaging a probe card on said wafer and applying said voltage through said probe card.

13. The method of claim 2 further including the steps of engaging a probe card on said wafer and applying said voltage through said probe card.

14. The method of claim 3 further including the steps of engaging a probe card on said wafer and applying said voltage through said probe card.

15. The method of claim 9 further including the steps of engaging a probe card on said wafer and applying said voltage through said probe card.

16. The method of claim 10 further including the steps of engaging a probe card on said wafer and applying said voltage through said probe card.

17. The method of claim 11 further including the steps of engaging a probe card on said wafer and applying said voltage through said probe card.

4. A method for inspecting micromechanical spatial light modulators, comprising the steps of:

(a) providing a semiconductor device having a plurality of reflective objects to be tested, each of said reflective objects being mechanically positionable in response to a predetermined signal applied to said semiconductor device;

(b) positioning an input to a vision system adjacent a predetermined one of said reflective objects to be tested;

(c) producing a series of optical test images on said reflective object to be tested in response to a series of at least two different signals applied to said semiconductor device;

(d) capturing an indication of said test images at said input reflected to said vision system;

(e) storing said indication of said reflected test images;

(f) transferring said indication of said reflected test images to a digital signal processor;

(g) moving said input to be adjacent to a new reflective object to be tested;

(h) analyzing said indication of said test images in parallel with said moving step and producing results of said analysis; and

(i) repeating all of the above steps until all objects have been analyzed, or a result is reached that indicates that an object is inoperable.

5. The method of claim 4 wherein said series of test images includes at least one ON image.

6. The method of claim 4 wherein said series of test images includes at least one OFF image.

7. The method of claim 4 wherein said series of test images includes a checkerboard pattern.

8. An automated inspection system for micromechanical devices, comprising:

(a) said system of micromechanical devices coupled to and controlled by a semiconductor device, each of said micromechanical devices having a reflective element;

(b) a system controller operable to receive user inputs on operation of said system;

(c) a vision system for viewing said micromechanical devices and individual reflective elements on said micromechanical devices;

(d) a vision system controller operable to monitor and analyze operation of said micromechanical devices and said elements, including;

(e) an input for capturing reflected images from said micromechanical devices and said elements;

(f) a memory for storing indicia of said reflected images;

(g) a digital signal processor for analyzing said indicia of said reflected images; and

(h) a mechanical controller for moving said input in response to a predetermined condition; and

(i) a stage for mounting said semiconductor devices.