MEMS thermal actuator and method of manufacture

• US 7,622,783 B2
• Filed: 02/14/2007
• Issued: 11/24/2009
• Est. Priority Date: 02/14/2007
• Status: Active Grant

• Current Assignee: Innovative Micro Technology Incorporated
• Original Assignee: Innovative Micro Technology Incorporated
• Inventors: Foster, John S., Carlson, Gregory A., Gudeman, Christopher S., Rubel, Paul J.
• Primary Examiner(s): LOUIE, WAI SING
• Application Number:
  US11/705,739
• Publication Number:
  US 20080191303A1
• Time in Patent Office: 1,014 Days
• Field of Search: 257/108, 257/415, 257/428, 438/50, 438/52
• US Class Current: 257/415
• CPC Class Codes: H01H 1/0036 Switches making use of microelectromechanical systems [MEMS] for electromagnetic relays H01H50/005; for electrostatic relays H01H59/0009
• CPC Class Codes: H01H 2001/0047 operable only by mechanical latching
• CPC Class Codes: H01H 2001/0078 with parallel movement of the movable contact relative to the substrate
• CPC Class Codes: H01H 2061/006 Micromechanical thermal relay
• CPC Class Codes: H01H 2061/008 Micromechanical actuator with a cold and a hot arm, coupled together at one end
• CPC Class Codes: H01H 61/04 wherein the thermally-sensitive member is only heated directly

Abstract

A separated MEMS thermal actuator is disclosed which is largely insensitive to creep in the cantilevered beams of the thermal actuator. In the separated MEMS thermal actuator, a inlaid cantilevered drive beam formed in the same plane, but separated from a passive beam by a small gap. Because the inlaid cantilevered drive beam and the passive beam are not directly coupled, any changes in the quiescent position of the inlaid cantilevered drive beam may not be transmitted to the passive beam, if the magnitude of the changes are less than the size of the gap.

Claims

1. A micromechanical actuator, comprising:

a silicon-on-insulator substrate having a device layer formed in a plane;

a metallic material inlaid in the plane of the device layer and configured to move substantially in the plane of the device layer;

a silicon member formed from the device layer of a silicon-on-insulator substrate, configured to move substantially in the plane of the device layer, wherein movement of the inlaid material drives movement of the silicon member.

2. The micromechanical actuator of claim 1, wherein the inlaid material moves about a proximal end, the proximal end being anchored to the silicon-on-insulator substrate, when the inlaid material is heated.

3. The micromechanical actuator of claim 2, wherein the inlaid material extends substantially through the plane of the device layer, and is coupled at its distal end by a dielectric tether to an adjunct silicon portion.

4. The micromechanical actuator of claim 3, wherein the adjunct silicon portion is separated from the silicon member by an air gap in a quiescent state, and the inlaid material closes the air gap and drives movement of the silicon member when the micromechanical actuator is energized.

5. The micromechanical actuator of claim 4, wherein surfaces which define the air gap comprise at least one of silicon nitride, silicon dioxide, an inlaid metal, an inlaid semiconductor and a hydrofluoric acid etch-resistant polymer.

6. The micromechanical actuator of claim 1, further comprising a metal contact electrode which overhangs a wall on a distal end of the silicon member, the wall of the silicon member being disposed perpendicularly with respect to the plane of the device layer.

7. The micromechanical actuator of claim 1, further comprising a metal contact electrode inlaid in the plane of the device layer, and contiguous with a distal end of the silicon member.

8. A micromechanical switch comprising at least one micromechanical actuator of claim 1 and at least one additional micromechanical actuator, each micromechanical actuator configured to move substantially perpendicularly with respect to the other, in order to make contact between contact electrodes disposed on the distal ends of the micromechanical actuators.

9. An array of micromechanical switches, comprising at least one of the micromechanical switches of claim 1.

10. The array of micromechanical switches of claim 9, wherein electrical contact to the inlaid material is made by vias formed in the silicon-on-insulator substrate.

11. The array of micromechanical switches of claim 10, further comprising a lid wafer with at least one device cavity formed therein, which encloses the array of micromechanical switches.

12. The array of micromechanical switches of claim 11, wherein electrical contact to the micromechanical switches is made by vias formed through the thickness of the lid wafer.

13. The micromechanical actuator of claim 1, wherein, wherein the inlaid metallic material comprises at least one of a magnetically permeable material, gold, a gold alloy, nickel, a nickel alloy, aluminum, permalloy, platinum, and copper.

14. The micromechanical actuator of claim 6, wherein the contact electrode comprises at least one of gold, a gold alloy, rhodium, ruthenium, platinum, nickel, a nickel alloy, aluminum and copper, and the silicon member comprises single crystal silicon.

15. The micromechanical actuator of claim 1, wherein a top surface of the inlaid metallic material is substantially flush with a top surface of the device layer.

16. A micromechanical actuator, comprising:

a silicon-on-insulator substrate having a device layer formed in a plane;

a material inlaid in the plane of the device layer and configured to move substantially in the plane of the device layer;

a silicon member formed from the device layer of a silicon-on-insulator substrate, configured to move substantially in the plane of the device layer, wherein movement of the inlaid material drives movement of the silicon member,

wherein the silicon member is clad with a metal contact material.