Multi-phased MEMS plate lowering and lifting system and method

Patent metadata

Field	Value
Publication number	US-9550665-B2
Application number	US-201414488616-A
Country	US
Kind code	B2
Filing date	Sep 17, 2014
Priority date	Sep 17, 2014
Publication date	Jan 24, 2017
Grant date	Jan 24, 2017

Abstract

A MEMS device includes a bottom plate structure supporting a conductive electrode. A flexible conductive top plate movably supported by a flexure is affixed to a small peripheral portion of the top plate that is aligned with the electrode. Drive circuitry applies a high level of a drive voltage signal between the electrode and the top plate to produce an attracting electrostatic force between the top plate and the electrode sufficient to overcome the flexure and draw the top plate against the electrode. The drive circuitry later applies a low level of the drive voltage signal to remove the electrostatic force and allow the flexure to peel the peripheral portion away from the electrode. Additional drive voltage signals may be applied to additional electrodes to draw additional peripheral portions of the top plate against the additional electrodes and successively removed to allow peripheral portions of the top plate to be sequentially peeled away from the electrodes.

First claim

What is claimed is:

1. A MEMS (micro-electromechanical system) device comprising:
a bottom plate structure supporting conductive electrodes, including at least first, second and third electrodes;
a conductive top plate supported by spring structures affixed to peripheral portions of the top plate, wherein the top plate is generally aligned parallel with the first, second and third electrodes; and
electrode drive circuitry for: applying a first level of a drive voltage signal between the top plate and each of the first, second and third electrodes, to produce an attractive electrostatic force between the top plate and each of the first, second and third electrodes, sufficient to flex the spring structures and draw the top plate against each of the first, second and third electrodes; and sequentially applying a second level of the drive voltage signal between the top plate and successive ones of the first, second and third electrodes, to sequentially remove the attractive electrostatic force between the top plate and successive ones of the first, second and third electrodes sufficient to allow the spring structures to sequentially peel the peripheral portions away from the first, second and third electrodes.

2. The MEMS device of claim 1 wherein each of the spring structures includes a respective flexure.

3. The MEMS device of claim 1 comprising a conductive varactor plate supported by the bottom plate structure, the conductive varactor plate and the top plate forming an adjustable capacitor.

4. The MEMS device of claim 1 wherein stiction forces cause the top plate to tend to stick to the first, second and third electrodes, and wherein restoring forces produced by the spring structures are sufficient to break the stiction forces between the top plate and the first, second and third electrodes as the attractive electrostatic forces are sequentially removed.

5. The MEMS device of claim 1 wherein sequentially applying the second level of the drive voltage signal includes: abruptly transitioning the drive voltage signal from the first level to the second level between the top plate and successive ones of the first second and third electrodes.

6. The MEMS device of claim 1 wherein each of the spring structures has: a respective first portion affixed to a corresponding peripheral portion of the top plate; and a respective second portion affixed to a corresponding support.

7. The MEMS device of claim 5 wherein the transitioning is timed in accordance with a resonance property of the top plate.

8. The MEMS device of claim 1 wherein the conductive electrodes are composed of titanium-aluminum.

9. The MEMS device of claim 1 wherein the top plate is composed of titanium-aluminum.

10. The MEMS device of claim 2 wherein the flexures are composed of titanium-aluminum.

11. The MEMS device of claim 3 wherein the varactor plate is composed of titanium-aluminum.

12. The MEMS device of claim 1 wherein the peripheral portions include at least three corners of the top plate.

13. The MEMS device of claim 12 wherein the three corners of the top plate are respectively aligned with the first, second and third electrodes.

14. The MEMS device of claim 13 wherein the spring structures include at least three spring structures respectively affixed to the three corners of the top plate.

15. A method for operating a MEMS (micro-electromechanical system) device, the method comprising:
applying a first level of a drive voltage signal between a conductive top plate and conductive electrodes, including at least first, second and third electrodes, to produce an attractive electrostatic force between the top plate and each of the first, second and third electrodes, sufficient to flex spring structures affixed to peripheral portions of the top plate and draw the top plate against each of the first, second and third electrodes; wherein the conductive electrodes are supported by a bottom plate structure, the top plate is supported by the spring structures, and the top plate is generally aligned parallel with the first, second and third electrodes; and
sequentially applying a second level of the drive voltage signal between the top plate and successive ones of the first, second and third electrodes, to sequentially remove the attractive electrostatic force between the top plate and successive ones of the first, second and third electrodes, sufficient to allow the spring structures to sequentially peel the peripheral portions away from the first, second and third electrodes.

16. The method of claim 15 wherein stiction forces cause the top plate to tend to stick to the first, second and third electrodes, and wherein restoring forces produced by the spring structures are sufficient to break the stiction forces between the top plate and the first, second and third electrodes as the attractive electrostatic forces are sequentially removed.

17. The method of claim 15 wherein sequentially applying the second level of the drive voltage signal includes: abruptly transitioning the drive voltage signal from the first level to the second level between the top plate and successive ones of the first, second and third electrodes, timed in accordance with a resonance property of the top plate.

18. The method of claim 15 comprising: supporting a conductive varactor plate on the bottom plate structure, the conductive varactor plate and the top plate forming an adjustable capacitor.

19. A MEMS (micro-electromechanical system) device comprising:
a bottom plate structure supporting conductive electrodes, including at least first, second, third and fourth electrodes;
a conductive top plate supported by spring structures affixed to peripheral portions of the top plate, wherein the top plate is generally aligned parallel with the first, second, third and fourth electrodes; and
electrode drive circuitry for: applying a first level of a drive voltage signal between the top plate and each of the first, second, third and fourth electrodes, to produce an attractive electrostatic force between the top plate and each of the first, second, third and fourth electrodes, sufficient to flex the spring structures and draw the top plate against each of the first, second, third and fourth electrodes; and sequentially applying a second level of the drive voltage signal between the top plate and successive ones of the first, second, third and fourth electrodes, to sequentially remove the attractive electrostatic force between the top plate and successive ones of the first, second, third and fourth electrodes, sufficient to allow the spring structures to sequentially peel the peripheral portions away from the first, second, third and fourth electrodes.

20. The MEMS device of claim 19 wherein the peripheral portions include at least four corners of the top plate.

21. The MEMS device of claim 20 wherein the four corners of the top plate are respectively aligned with the first, second, third and fourth electrodes.

22. The MEMS device of claim 21 wherein the spring structures include at least four spring structures respectively affixed to the four corners of the top plate.

23. The MEMS device of claim 19 wherein stiction forces cause the top plate to tend to stick to the first, second, third and fourth electrodes, and wherein restoring forces produced by the spring structures are sufficient to break the stiction forces between the top plate and the first, second, third and fourth electrodes as the attractive electrostatic forces are s

Assignees

• Texas Instruments Inc

Inventors

• Barker Paul G

Classifications

• H01G5/16 Primary

  using variation of distance between electrodes · CPC title

• B81B3/0013 Primary

  Structures dimensioned for mechanical prevention of stiction, e.g. spring with increased stiffness · CPC title

• H02N1/006

  of the gap-closing type (H02N1/004 takes precedence) · CPC title

• B81B2203/04

  Electrodes · CPC title

• B81C1/00976

  Control methods for avoiding stiction, e.g. controlling the bias voltage · CPC title