MICROMIRROR AND FABRICATION METHOD FOR PRODUCING MICROMIRROR

• US 20100033788A1
• Filed: 08/03/2009
• Published: 02/11/2010
• Est. Priority Date: 08/01/2008
• Status: Abandoned Application

• Current Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Original Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Inventors: Nelson, Thomas, McManamon, Paul, Maley, Sarah, Wu, Lei, Pais, Andrea, Xie, Huikai, Jia, Kemiao
• Application Number:
  US12/534,514
• Publication Number:
  US 20100033788A1
• Time in Patent Office: Days
• US Class Current: 359/198.100
• CPC Class Codes: G06Q 10/06 Resources, workflows, human or project management; Enterprise or organisation planning; Enterprise or organisation modelling
• CPC Class Codes: G06Q 10/06313 Resource planning in a project environment
• CPC Class Codes: G06Q 30/0601 Electronic shopping [e-shopping]
• CPC Class Codes: G06Q 40/12 Accounting

Abstract

A high-fill-factor and large-aperture tip-tilt micromirror array is disclosed. Electrothermal actuation can be used to obtain a large scan range, and the actuation engine can be hidden underneath the mirror plate for high fill factor. In one embodiment, inverted-series-connected (ISC) bimorph actuators can be used to achieve tilt and piston scanning. Embodiments can be used to implement optical phased array technology for steering active and passive electro-optical systems based on MEMS mirrors.

Claims

1. A micromirror structure, comprising:

at least one micromirror, wherein each micromirror comprises;

a mirror plate;

a pillar structure; and

at least one electrothermal actuator,

wherein the pillar structure interconnects the at least one electrothermal actuator to the mirror plate, wherein at least a portion of one or more of the at least one electrothermal actuator is positioned under the mirror plate.

2. The micromirror structure according to claim 1, wherein the at least one micromirror comprises a plurality of micromirrors forming an array of micromirrors.

3. The micromirror according to claim 1, wherein the one or more of the at least one electrothermal actuator is positioned entirely under the mirror plate.

4. The micromirror according to claim 3, wherein activation of the at least one electrothermal actuator causes the micromirror to scan angularly in one dimension.

5. The micromirror according to claim 3, wherein activation of the at least one electrothermal actuator causes the micromirror to scan angularly in two dimension.

6. The micromirror according to claim 3, wherein activation of the at least one electrothermal actuator causes the micromirror to scan linearly.

7. The micromirror according to claim 3, wherein at least one micromirror comprises a plurality of micromirrors forming an array of micromirrors.

8. The micromirror structure according to claim 3, wherein the mirror plate is formed of single-crystal silicon.

9. The micromirror structure according to claim 3, wherein the mirror plate is coated with a metal.

10. The micromirror structure according to claim 3, wherein the mirror plate is coated with a multi-layer thin-film stack.

11. The micromirror structure according to claim 3, wherein each of the at least one electrothermal actuator is positioned entirely under the mirror plate.

12. The micromirror structure according to claim 3, wherein each of the at least one electrothermal actuator comprises a plurality of layers, wherein at least two of the plurality of layer have different coefficients of thermal expansion.

13. The micromirror structure according to claim 3, wherein each of the at least one electrothermal actuator comprises an S-shaped inverted-series-connected bimorph actuator.

14. The micromirror structure according to claim 3, wherein each of the at least one electrothermal actuator comprises a dual inverted-series-connected bimorph actuator.

15. The micromirror structure according to claim 7, wherein the array is an optical phased array.

16. The micromirror structure according to claim 7, wherein the array has a fill factor of at least 90%.

17. The micromirror structure according to claim 7, wherein the array has a fill factor of at least 95%.

18. The micromirror structure according to claim 7, wherein each actuator spans less than ⅓

of the length of the mirror plate.

19. The micromirror structure according to claim 7, wherein the array has an aperture in the range 5 mm to 12.5 mm.

20. The micromirror structure according to claim 7, wherein each mirror plate has a length in the range 1 mm to 10 mm.

21. The micromirror structure according to claim 7, wherein each micromirror is independently controlled with respect to rotation and piston motion.

22. The micromirror structure according to claim 7, wherein adjacent mirror plates have a separation from each other in the range 10 μ

m to 200 μ

m.

23. A method of fabricating at least one micromirror, wherein each micromirror comprises:

a mirror plate;

a pillar structure;

at least one electrothermal actuator;

wherein the pillar structure interconnects the at least one electrothermal actuator to the mirror plate, wherein at least a portion of one or more of the at least one electrothermal actuator is positioned below the mirror plate, wherein the method comprises;

preparing a silicon-on-insulator substrate;

fabricating the at least one electrothermal actuator on a front side of the silicon-on-insulator substrate; and

fabricating the mirror plate on a back side of the silicon-on-insulator substrate, wherein at least a portion of an inner silicon region of the silicon-on-insulator substrate is removed to create the pillar structure.

24. The method according to claim 23, further comprising:

bonding the front side of the silicon-on-insulator substrate to a carrier substrate.

25. The method according to claim 24, wherein the bonding is wafer-level.

26. The method according to claim 24, wherein the bonding is flip-chip bonding.

27. The method according to claim 24, wherein the at least one electrothermal actuator is released before the bonding.

28. The method according to claim 24, wherein the at least one electrothermal actuator is released after the bonding.

29. The method according to claim 23, wherein fabricating the at least one electrothermal actuator is done via an anisotropic silicon etch and an isotropic silicon etch.

30. The method according to claim 29, wherein the silicon etch is stopped by a buried oxide layer of the silicon-on-insulator substrate.

31. The method according to claim 27, wherein the carrier substrate has a recess to protect the at least one electrothermal actuator during bonding.

32. The method according to claim 28, wherein the carrier substrate has a through hole that allows the release of the at least one electrothermal actuator after bonding.

33. The method according to claim 24, wherein the carrier substrate has at least one through-silicon via for direct surface mounting.