High voltage micromachined electrostatic switch

• US 6,229,683 B1
• Filed: 06/30/1999
• Issued: 05/08/2001
• Est. Priority Date: 06/30/1999
• Status: Expired due to Term

• Current Assignee: Research Triangle Institute
• Original Assignee: MCNC, Inc.
• Inventors: Goodwin-Johansson, Scott Halden
• Primary Examiner(s): SHERRY, MICHAEL JUDE
• Application Number:
  US09/345,722
• Time in Patent Office: 678 Days
• Field of Search: 361/230-235, 361/207, 200/181
• US Class Current: 361/233
• CPC Class Codes: H01H 1/20 Bridging contacts for circuit breakers H01H73/045
• CPC Class Codes: H01H 2037/008 Micromechanical switches operated thermally
• CPC Class Codes: H01H 2059/0081 with a tapered air-gap between fixed and movable electrodes
• CPC Class Codes: H01H 59/0009 making use of micromechanics

Abstract

A MEMS (Micro Electro Mechanical System) electrostatically operated high voltage switch or relay device is provided. This device can switch high voltages while using relatively low electrostatic operating voltages. The MEMS device comprises a microelectronic substrate, a substrate electrode, and one or more substrate contacts. The MEMS device also includes a moveable composite overlying the substrate, one or more composite contacts, and at least one insulator. In cross section, the moveable composite comprises an electrode layer and a biasing layer. In length, the moveable composite comprises a fixed portion attached to the underlying substrate, a medial portion, and a distal portion moveable with respect to the substrate electrode. The distal and/or medial portions of the moveable composite are biased in position when no electrostatic force is applied. Applying a voltage between the substrate electrode and moveable composite electrode creates an electrostatic force that attracts the moveable composite to the underlying microelectronic substrate. The substrate contact and composite contact are selectively interconnected in response to the application of electrostatic force. Once electrostatic force is removed, the moveable composite reassumes the biased position such that the substrate and composite contacts are disconnected. Various embodiments further define components of the device. Other embodiments further include a source of electrical energy, a diode, and a switching device connected to different components of the MEMS device. A method of using the aforementioned electrostatic MEMS device is provided.

Claims

1. A MEMS device driven by electrostatic forces, comprising:

a microelectronic substrate supporting the MEMS device and defining a planar surface;

a substrate electrode forming a layer on the surface of said substrate;

a substrate contact attached to said substrate;

a moveable composite overlying said substrate electrode and having an electrode layer and a biasing layer, said moveable composite having a fixed portion attached to the underlying substrate, and a distal portion movable with respect to said substrate electrode;

a composite contact attached to said moveable composite; and

an insulator electrically separating said substrate electrode from said moveable electrode,

whereby said composite contact and said substrate contact are electrically connected when said moveable composite distal portion is attracted to said substrate.

2. A MEMS device according to claim 1, wherein said distal portion of said moveable composite is positionally biased with respect to said microelectronic substrate.

3. A MEMS device according to claim 1 wherein said moveable composite substantially conforms to the surface of said microelectronic substrate when said moveable composite distal portion is attracted to said substrate.

4. A MEMS device according to claim 1 wherein the electrode layer and the biasing layer of said moveable composite are formed from one or more generally flexible materials.

5. A MEMS device according to claim 1 wherein said substrate contact is generally flush with the upper surface of said substrate.

6. A MEMS device according to claim 1 wherein said substrate contact protrudes from the upper surface of said substrate.

7. A MEMS device according to claim 1 wherein said substrate contact has at least one generally smooth surface.

8. A MEMS device according to claim 1 wherein said substrate contact has at least one generally rough surface.

9. A MEMS device according to claim 1 wherein said substrate contact comprises a plurality of contacts.

10. A MEMS device according to claim 9 wherein at least two of said plurality of contacts are connected in series.

11. A MEMS device according to claim 9 wherein at least two of said plurality of contacts are connected in parallel.

12. A MEMS device according to claim 9 wherein said moveable composite forms a trough, and wherein at least two of said plurality of contacts are disposed perpendicular to the trough.

13. A MEMS device according to claim 1 wherein said substrate contact is electrically isolated from said substrate electrode.

14. A MEMS device according to claim 1, wherein said substrate electrode underlies substantially the entire area of the distal portion of said moveable composite.

15. A MEMS device according to claim 1, wherein said insulator is attached to and overlies said substrate electrode.

16. A MEMS device according to claim 1, further comprising an insulator between said substrate contact and said substrate electrode.

17. A MEMS device according to claim 1, wherein said composite biasing layer comprises at least one polymer film.

18. A MEMS device according to claim 1, wherein said composite biasing layer comprises polymer films on opposite sides of said composite electrode layer.

19. A MEMS device according to claim 1 wherein said composite biasing layer and electrode layer have different thermal coefficients of expansion, urging said moveable composite to curl.

20. A MEMS device according to claim 1 wherein said composite biasing layer comprises at least two polymer films of different thicknesses, urging said moveable composite to curl.

21. A MEMS device according to claim 1 wherein said composite biasing layer comprises at least two polymer films of different coefficients of expansion, urging said moveable composite to curl.

22. A MEMS device according to claim 1, wherein the distal portion of said moveable composite curls out of the plane defined by the upper surface of said moveable composite when no electrostatic force is created between said composite electrode and said moveable electrode.

23. A MEMS device according to claim 22 wherein said moveable composite has different radii of curvature at different locations along the distal portion.

24. A MEMS device according to claim 1, wherein said composite contact is electrically isolated from said composite electrode.

25. A MEMS device according to claim 1, wherein said composite contact is generally flush with the lower surface of said moveable composite.

26. A MEMS device according to claim 1, wherein said composite contact protrudes from the lower surface of said moveable composite.

27. A MEMS device according to claim 1 wherein said composite contact has at least one generally smooth surface.

28. A MEMS device according to claim 1 wherein said composite contact has at least one generally rough surface.

29. A MEMS device according to claim 1, wherein said composite contact comprises a plurality of contacts.

30. A MEMS device according to claim 29 wherein at least two of said plurality of contacts are connected in series.

31. A MEMS device according to claim 29 wherein at least two of said plurality of contacts are connected in parallel.

32. A MEMS device according to claim 29, wherein at least one of said composite contacts is electrically isolated from said composite electrode.

33. A MEMS device according to claim 1, wherein the surface area of said substrate electrode comprises generally the same surface area as said moveable electrode.

34. A MEMS device according to claim 1, wherein said substrate electrode generally encompasses said substrate contact.

35. A MEMS device according to claim 1, wherein said composite electrode layer generally encompasses said composite contact.

36. A MEMS device according to claim 1, wherein the shape of said substrate electrode is generally the same as the shape of said moveable electrode.

37. A MEMS device according to claim 1, wherein said moveable composite has a generally rectangular shape.

38. A MEMS device according to claim 1, further comprising a source of electrical energy electrically connected to at least one of said substrate contact and said composite contact.

39. A MEMS device according to claim 38, further comprising at least one device electrically connected to at least one of said substrate contact and said composite contact.

40. A MEMS device according to claim 1, further comprising a source of electrical energy electrically connected to at least one of said substrate electrode and said composite electrode.

41. A MEMS device according to claim 40, further comprising a switching device electrically connected to at least one of said substrate electrode and said composite electrode.

42. A method of using a MEMS device solely supported by a microelectronic substrate having a substrate electrode and a substrate contact, and a moveable composite having an electrode layer and a composite contact, said moveable composite movable in response to an electrostatic force created between the substrate electrode and the electrode layer, the method comprising the steps of:

electrically isolating at least one of the substrate contact or the composite contact from its respective associated substrate electrode or composite electrode,

selectively generating an electrostatic force between the substrate electrode and the electrode layer of said moveable composite;

moving said moveable composite toward the substrate; and

electrically connecting the substrate contact and composite contact in a circuit electrically isolated from at least one of the substrate electrode or composite electrode.