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

• US 20020079550A1
• Filed: 03/01/2001
• Published: 06/27/2002
• Est. Priority Date: 04/10/2000
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: ONIX Microsystems Incorporated
• Inventors: Behin, Berhang, Daneman, Michale J.
• Granted Patent: US 6,528,887 B2
• Time in Patent Office: Days
• US Class Current: 257/459
• 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 and protruding from 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.

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 2, further comprising a voltage source controllably coupled to the flap 4. The device of claim 2, further comprising at least one flexure coupled to the flap.

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

7. The device of claim 6 wherein the base landing pads are insulated from the base and electrically coupled to be equipotential with the flap.

8. 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.

9. The device of claim 8, 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.

10. The device of claim 9, further comprising a flexure coupled to the flap.

11. The device of claim 10, wherein the flexure provides an electrical connection between the one or more top landing pads and the sidewall.

12. The device of claim 9 wherein the flexure is a MEMs spring.

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

14. The device of claim 13, wherein the flexure provides an electrical connection between a switch and the flap.

15. 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 coupledsuch that they are substantially equipotential to the flap.

16. The device of claim 15, further comprising a voltage source selectively coupledbetween the sidewall and the flap.

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

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

20. The method of claim 19, wherein the landing surface is the base and the one or more landing areas are substantially equipotential to the base.

21. The method of claim 20 further comprising the step of providing a sidewall for limiting the motion of the flap.

22. The method of claim 21 wherein the flap includes one or more top landing pads, wherein the top landing pads are electrically isolated from the flap and electrically connected to the sidewall such that they are substantially equipotential to the sidewall.

23. The method of claim 21, 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.

25. ) 9. The device of claim 24, further comprising a sidewall for limiting the motion of the flap, wherein the one or more top landing areas are electrically connected such that the sustain equipotential with the sidewall.

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

27. ) The method of claim 25, wherein the sidewall includes one or more sidewall landing areas wherein the one or more sidewall landing areas 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.

5. The device of claim 4, wherein at least one flexure provides an electrical to the landing pads.

19. A method for operating a MEMS device, comprising the steps of:

a) providing a base;

b) providing a flap having a bottom portion movable to the base such that the flap is movable with respect to a plane of the base from a first angular orientation to a second angular orientation, wherein the flap includes one or more electrically conductive landing areas connected to a surface of an underside of the flap; and

c) electrically coupling the one or more landing areas to a landing surface

24. 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

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