Micro mechanical device with memory metal component

• US 6,072,617 A
• Filed: 11/20/1997
• Issued: 06/06/2000
• Est. Priority Date: 11/26/1996
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Henck, Steven A.
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Lester, Evelyn A.
• Application Number:
  US08/975,547
• Time in Patent Office: 929 Days
• Field of Search: 359/237, 359/224
• US Class Current: 359/237
• CPC Class Codes: C22F 1/006 Resulting in heat recoverable alloys with a memory effect
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A method of preventing permanent deformation of deflecting metal components of micro mechanical devices, such as hinges (12) of mirror elements (10) of a digital micro mirror device. The hinges (12) are made from a memory metal capable of undergoing austenite/martensite phase transitions. If the device is operated and the hinges (12) become mechanically distorted, the hinges (12) can be heated to cause a transition to the austenite phase and a return to their original shape.

Claims

1. A method of fabricating a micro-mechanical device having a deflectable metal strip component, said micro-mechanical device having an expected operating temperature such that mechanical distortion during operation of the device is reversible, comprising the steps of:

providing a metal capable of phase changes in the solid state and having a phase transition temperature that is above said operating temperature;

fabricating said component from said metal;

forming said component to its desired shape;

applying an electrical current through said component to anneal said component to cause a phase transition of said component to train said component in one said phase; and

completing fabrication of said device;

further including the steps of utilizing the completed device and then periodically applying said electrical current through said component to again cause said phase transition.

2. The method of claim 1, wherein said component is a hinge.

3. The method of claim 2, wherein said device is a digital micro mirror device.

4. The method of claim 1, wherein said component is a cantilevered metal strip, fixed at one end.

5. The method of claim 1, wherein said phase changes are austenite/martensite phase changes and said annealing step causes a transition to said austenite phase.

6. The method of claim 1, wherein said metal is primarily nickel titanium.

7. The method of claim 1 further including the steps of utilizing the completed device and then periodically applying said electrical current through said component to again cause said phase transition.

8. A method of fabricating a micro-mechanical device having a deflectable metal strip component, said micro-mechanical device having an expected operating temperature such that mechanical distortion during operation of the device is reversible, comprising the steps of:

providing a metal film capable of phase changes in the solid state and having a phase transition temperature that is below said operating temperature;

fabricating said component from said metal film such that deflection of said component will result in a phase change of said component to a first said phase;

forming said component to its desired shape;

applying an electrical current through said component to anneal said component to cause a phase transition of said component to train said component in one said phase; and

completing fabrication of said device;

further including the steps of utilizing the completed device and then periodically applying said electrical current through said component to again cause said phase transition.

9. The method of claim 8, wherein said component is a hinge.

10. The method of claim 8, wherein said device is a digital micro mirror device.

11. The method of claim 8, wherein said component is a cantilevered metal strip, fixed at one end.

12. The method of claim 8, wherein said phase changes are austenite/martensite phase changes and said annealing step causes a transition to said austenite phase.

13. The method of claim 8, wherein said metal is primarily nickel titanium.

14. The method of claim 8 further including the steps of utilizing the completed device and then periodically applying said electrical current through said component to again cause said phase transition.

15. A method of fabricating a micro-mechanical device having a deflectable metal strip component, said micro-mechanical device having an expected operating temperature such that mechanical distortion during operation of the device is reversible, comprising the steps of:

providing a metal capable of phase changes in the solid state and having a phase transition temperature that is above said operating temperature;

fabricating said component from said metal;

forming said component to its desired shape;

applying an electrical current through said component to anneal said component to cause a phase transition of said component to train said component in one said phase; and

completing fabrication of said device;

wherein said step of applying an electrical current is provided during fabrication of said device.

16. The method of claim 15 wherein said component is a hinge.

17. The method of claim 16 wherein said device is a digital micro mirror device.

18. The method of claim 15 wherein said component is a cantilevered metal strip, fixed at one end.

19. The method of claim 15 wherein said phase changes are austenite/martensite phase changes and said annealing step causes a transition to said austenite phase.

20. The method of claim 15 wherein said metal is primarily nickel titanium.

21. A method of fabricating a micro-mechanical device having a deflectable metal strip component, said micro-mechanical device having an expected operating temperature such that mechanical distortion during operation of the device is reversible, comprising the steps of:

providing a metal film capable of phase changes in the solid state and having a phase transition temperature that is below said operating temperature;

fabricating said component from said metal film such that deflection of said component will result in a phase change of said component to a first said phase;

forming said component to its desired shape;

applying an electrical current through said component to anneal said component to cause a phase transition of said component to train said component in one said phase; and

completing fabrication of said device;

wherein said step of applying an electrical current is provided during fabrication of said device.

22. The method of claim 21 wherein said component is a hinge.

23. The method of claim 22 wherein said device is a digital micro mirror device.

24. The method of claim 21 wherein said component is a cantilevered metal strip, fixed at one end.

25. The method of claim 21 wherein said phase changes are austenite/martensite phase changes and said annealing step causes a transition to said austenite phase.

26. The method of claim 21 wherein said metal is primarily nickel titanium.