Conductive equipotential landing pads formed on the underside of a MEMS device

• US 6,528,887 B2
• Filed: 03/01/2001
• Issued: 03/04/2003
• Est. Priority Date: 04/10/2000
• Status: Expired due to Term

• Current Assignee: Analog Devices, Inc.
• Original Assignee: ONIX Microsystems Incorporated
• Inventors: Behin, Behrang, Daneman, Michael J.
• Primary Examiner(s): Clark, Jasmine J B
• Application Number:
  US09/798,129
• Publication Number:
  US 20020079550A1
• Time in Patent Office: 733 Days
• Field of Search: 257/774, 257/750, 257/758, 257/773, 257/731, 257/734, 257/444, 257/739, 257/786, 438/629, 438/637, 438/652, 438/118, 438/622, 438/618, 438/666, 438/48
• US Class Current: 257/774
• CPC Class Codes: B81B 3/0008 Structures for avoiding electrostatic attraction, e.g. avoiding charge accumulation
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• CPC Class Codes: B81B 3/0051 For defining the movement, i.e. structures that guide or limit the movement of an element mechanical arrangements for preventing or damping vibration or shock H01H3/60
• 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
• CPC Class Codes: G02B 26/085 the reflecting means being moved or deformed by electromagnetic means

Abstract

A MEMS device with a flap having one or more conductive landing areas electrically isolated from the flap and electrically coupled to a landing surface to reduce stiction. The device may be formed from a device layer of a silicon-on-insulator (SOI) substrate with conductive landing pads fabricated by forming one or more vias through the device layer, an underlying sacrificial layer etched to form one or more depressions at locations corresponding the vias and filled with a conductive landing pad material to form a structure having one or more electrically isolated landing pad areas on an underside of the device layer. A method for operating a MEMs device in an equipotential stiction reduction mode is also provided.

Claims

1. A MEMS device comprising

a) a base;

b) a flap having a bottom portion movably coupled to the base such that the flap is movable with respect to a plane of the base from a first orientation to a second orientation; and

c) one or more electrically conductive landing pads connected to the flap, wherein the one or more landing pads are electrically isolated from the flap and electrically coupled to be equipotential with a landing surface.

2. The device of claim 1, wherein the landing surface is a surface of the base and the one or more landing pads are electrically equipotential to the base.

3. The device of claim 1, further comprising one or more electrically conductive base landing pads protruding from a surface of the base.

4. The device of claim 1, further comprising one or more electrically conductive top landing pads protruding from a top surface of the flap, wherein the top landing pads are electrically isolated from the flap.

5. The device of claim 1 further comprising one or more flexures attached to the flap.

6. The device of claim 1 further comprising a sidewall for limiting the motion of the flap, the sidewall having one or more sidewall landing pads that are electrically isolated from the sidewall and electrically coupled such that they are substantially equipotential to the flap.

7. The device of claim 1 wherein the device is a microelectromechanical mirror.

8. The device of claim 1 wherein the device is formed from a silicon on insulator substrate.

9. The device of claim 1 wherein one or more of the landing pads protrude from the flap.

10. The device of claim 1 wherein the one or more of the landing pads are configured flush to the flap.

11. The device of claim 1 wherein the device is an optical fiber switching array.

12. The device of claim 2, further comprising a voltage source controllably coupled to the flap.

13. The device of claim 2, further comprising at least one flexure coupled to the flap.

14. The device of claim 13, wherein at least one flexure provides an electrical to the landing pads.

15. The device of claim 3 wherein the base landing pads are insulated from the base and electrically coupled to be equipotential with the flap.

16. The device of claim 4, further comprising a sidewall for limiting the motion of the flap, wherein the one or more top landing pads are electrically connected such that the sustain equipotential with the sidewall.

17. The device of claim 16, further comprising a flexure coupled to the flap.

18. The device of claim 16 wherein the flexure is a MEMs spring.

19. The device of claim 17, wherein the flexure provides an electrical connection between the one or more top landing pads and the sidewall.

20. The device of claim 5, wherein the flexure provides an electrical connection between a switch and the flap.

21. The device of claim 6, further comprising a voltage source selectively coupled between the sidewall and the flap.

22. A MEMS device comprising

a) base;

b) a flap having a bottom portion movably coupled to the base such that the flap is movable with respect to a plane of the base from a first orientation to a second orientation; and

c) one or more electrically conductive landing pads connected to a surface of an underside of the flap, wherein the one or more landing pads are electrically isolated from the flap and electrically coupled to be equipotential with a landing surface.

23. The device of claim 22, further comprising a sidewall for limiting the motion of the flap, wherein one or more top landing pads are electrically connected such that they are substantially equipotential with the sidewall.

24. The device of claim 22, further comprising one or more electrically conductive top landing pads on a top surface of the flap, wherein the top landing pads are electrically isolated from the flap.

25. The device of claim 23, wherein the sidewall includes one or more sidewall landing pads wherein the one or more sidewall landing pads are electrically isolated from the sidewall, and wherein the one or more sidewall landing pads are connected to the flap such that they are substantially equipotential to the flap.