MEMS device having electrothermal actuation and release and method for fabricating

• US 20040012298A1
• Filed: 11/08/2002
• Published: 01/22/2004
• Est. Priority Date: 11/09/2001
• Status: Active Grant

• Current Assignee: AAC Technologies Pte Limited (AAC Technologies Holdings Inc.)
• Original Assignee: Coventor, Inc. (Lam Research Corporation)
• Inventors: DeReus, Dana Richard, Gilbert, John Richard, Sett, Subham, Cunningham, Shawn Jay
• Granted Patent: US 8,264,054 B2
• Time in Patent Office: Days
• US Class Current: 310/306
• CPC Class Codes: B81B 2201/014 having a cantilever fixed on one side connected to one or more dimples
• CPC Class Codes: B81B 2201/018 Switches not provided for in B81B2201/014 - B81B2201/016
• CPC Class Codes: B81B 2203/0118 Cantilevers
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 2207/07 Interconnects
• CPC Class Codes: B81B 3/0024 Transducers for transforming thermal into mechanical energy or vice versa, e.g. thermal or bimorph actuators electric motors using thermal effects H02N10/00
• 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: B81C 1/0015 Cantilevers switches using MEMS H01H1/0036; electrostatic relays using micromechanics H01H59/0009; microelectro-mechanical resonators H03H9/02244
• CPC Class Codes: B81C 2201/0107 Sacrificial metal
• CPC Class Codes: B81C 2201/0108 Sacrificial polymer, ashing of organics
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• CPC Class Codes: H01H 1/04 Co-operating contacts of different material
• CPC Class Codes: H01H 1/504 by thermal means
• CPC Class Codes: H01H 2001/0042 Bistable switches, i.e. having two stable positions requiring only actuating energy for switching between them, e.g. with snap membrane or by permanent magnet
• CPC Class Codes: H01H 2001/0063 having electrostatic latches, i.e. the activated position is kept by electrostatic forces other than the activation force
• CPC Class Codes: H01H 2001/0089 Providing protection of elements to be released by etching of sacrificial element; Avoiding stiction problems, e.g. of movable element to substrate
• CPC Class Codes: H01H 2059/0072 with stoppers or protrusions for maintaining a gap, reducing the contact area or for preventing stiction between the movable and the fixed electrode in the attracted position
• CPC Class Codes: H01H 2061/006 Micromechanical thermal relay
• CPC Class Codes: H01H 59/0009 making use of micromechanics
• CPC Class Codes: H01H 61/04 wherein the thermally-sensitive member is only heated directly
• CPC Class Codes: H01L 23/3735 : Laminates or multilayers, e.g. direct bond copper ceramic substrates
• CPC Class Codes: H01L 23/522 : including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
• CPC Class Codes: H01L 27/1203 : the substrate comprising an insulating body on a semiconductor body, e.g. SOI three-dimensional layout H01L27/0688
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 : Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/09701 : Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H02N 1/006 : of the gap-closing type H02N1/004 takes precedence
• CPC Class Codes: H02N 10/00 : Electric motors using thermal effects motors using expansion or contraction of bodies due to heating or cooling F03G7/06
• CPC Class Codes: Y10T 29/49222 : forming array of contacts or terminals

Abstract

MEMS Device having Electrothermal Actuation and Release and Method for Fabricating. According to one embodiment, a microscale switch is provided and can include a substrate and a stationary electrode and stationary contact formed on the substrate. The switch can further include a movable microcomponent suspended above the substrate. The microcomponent can include a structural layer including at least one end fixed with respect to the substrate. The microcomponent can further include a movable electrode spaced from the stationary electrode and a movable contact spaced from the stationary electrode. The microcomponent can include an electrothermal component attached to the structural layer and operable to produce heating for generating force for moving the structural layer.

Claims

1. A movable microcomponent suspended over a substrate, the microcomponent comprising:

(a) a structural layer including at least one end fixed with respect to the substrate;

(b) a movable electrode attached to the structural layer and separated from the substrate; and

(c) a first electrothermal component attached to the structural layer and operable to produce heat for deflecting the structural layer.

2. The microcomponent according to claim 1, wherein the microcomponent has a length defined generally between the at least one end of the structural layer and a distal end of the movable electrode, and having a width that is substantially constant along the length.

3. The microcomponent according to claim 1, wherein the structural layer has a second end freely suspended with respect to the substrate.

4. The microcomponent according to claim 1, wherein the structural layer comprises a nonconductive, resilient material.

5. The microcomponent according to claim 1, wherein the movable electrode comprises a metal material.

6. The microcomponent according to claim 1, wherein the movable electrode comprises a semiconductive material.

7. The microcomponent according to claim 1, wherein the movable electrode substantially covers an underside of the structural layer.

8. The microcomponent according to claim 7 further including an electrode interconnect attached to a top surface of the structural layer opposite from the movable electrode and having electrical communication with the movable electrode.

9. The microcomponent according to claim 8, wherein the movable electrode and electrode interconnect have substantially equal respective coefficients of thermal expansion.

10. The microcomponent according to claim 1, wherein the first electrothermal component has first and second terminal ends communicating with a current source.

11. The microcomponent according to claim 1, wherein the first electrothermal component is attached to a top side of the structural layer for producing heat on the top side of the structural layer to deflect the structural layer towards the substrate.

12. The microcomponent according to claim 1, wherein the first electrothermal component is attached to an underside of the structural layer for producing heat on the underside of the structural layer to deflect the structural layer away from the substrate.

13. The microcomponent according to claim 1, further including a second electrothermal component attached to an underside of the structural layer for producing heat on the underside of the structural layer to deflect the structural layer away from the substrate, and wherein the first electrothermal component is attached to a top side of the structural layer for producing heat on the top side of the structural layer to deflect the structural layer towards the substrate.

14. The microcomponent according to claim 1, wherein the first electrothermal component extends substantially the length of the structural layer.

15. The microcomponent according to claim 1, wherein the first electrothermal component includes at least one resistance path transition effecting an abrupt change in electrical resistance for generating heat at the location of the resistance path transition.

16. The microcomponent according to claim 1, wherein the first electrothermal component includes at least one resistance path transition positioned adjacent the at least one fixed end and effecting an abrupt change in electrical resistance for generating heat adjacent the at least one fixed end.

17. The microcomponent according to claim 1, further including a movable contact attached to the microcomponent.

18. The microcomponent according to claim 17, further including a contact interconnect attached an opposite side of the structural layer from the movable contact and having electrical communication with the movable contact.

19. A microelectromechanical device comprising a microcomponent structured according to any of claims 1-18.

20. A microelectromechanical device comprising an array of microcomponents structured according to any of claims 1-18.

21. A microscale switch for electrostatic and electrothermal actuation, the switch comprising:

(a) a substrate;

(b) a stationary electrode formed on the substrate;

(c) a stationary contact formed on the substrate; and

(d) a movable microcomponent suspended above the substrate, comprising;

(i) a structural layer including at least one end fixed with respect to the substrate;

(ii) a movable electrode spaced from the stationary electrode;

(iii) a movable contact spaced from the stationary contact; and

(iv) a first electrothermal component attached to the structural layer and operable to produce heating for generating force for moving the structural layer.

22. The switch according to claim 21, wherein the microcomponent has a length defined generally between the at least one end of the structural layer and a distal end of the movable electrode, and having a width that is substantially constant along the length.

23. The switch according to claim 21, wherein the structural layer comprises a nonconductive, resilient material.

24. The switch according to claim 21, wherein the movable electrode substantially covers an underside of the structural layer.

25. The switch according to claim 21, further including an electrode interconnect attached to a top surface of the structural layer opposite from the movable electrode and having electrical communication with the movable electrode.

26. The switch of claim 25, wherein the movable electrode and electrode interconnect have substantially equal respective coefficients of thermal expansion.

27. The switch according to claim 21, wherein the first electrothermal component has first and second terminal ends communicating with a current source.

28. The switch according to claim 21, wherein the first electrothermal component is attached to a top side of the structural layer for producing heat on the top side of the structural layer to deflect the structural layer towards the substrate.

29. The switch according to claim 21, wherein the first electrothermal component is attached to an underside of the structural layer for producing heat on the underside of the structural layer to deflect the structural layer away from the substrate.

30. The switch according to claim 21, including a second electrothermal component attached to an underside of the structural layer for producing heat on the underside of the structural layer to deflect the structural layer away from the substrate, and wherein the first electrothermal component is attached to a top side of the structural layer for producing heat on the top side of the structural layer to deflect the structural layer towards the substrate.

31. The switch according to claim 21, wherein the first electrothermal component extends substantially the length of the structural layer.

32. The switch according to claim 21, wherein the first electrothermal component includes at least one resistance path transition effecting an abrupt change in electrical resistance for generating heat at the location of the resistance path transition.

33. The switch according to claim 21, wherein the first electrothermal component includes at least one resistance path transition positioned adjacent the at least one fixed end and effecting an abrupt change in electrical resistance for generating heat adjacent the at least one fixed end.

34. A microelectromechanical device comprising a switch structured according to claim 21.

35. A microelectromechanical device comprising an array of switches structured according to claim 21.

36. A method for implementing a switching function in a microscale device, comprising:

(a) providing a stationary electrode and a stationary contact formed on a substrate;

(b) providing a movable microcomponent suspended above the substrate and comprising;

(i) a structural layer including at least one end fixed with respect to the substrate;

(ii) a movable electrode spaced from the stationary electrode;

(iii) a movable contact spaced from the stationary electrode, the movable contact being positioned farther from the at least one end than the movable electrode; and

(iv) a first electrothermal component attached to the structural layer;

(c) applying a voltage between the movable electrode and the stationary electrode to electrostatically couple the movable electrode with the stationary electrode, whereby the movable component is deflected toward the substrate and the movable contact moves into contact with the stationary contact to permit an electrical signal to pass through the movable and stationary contacts; and

(d) applying a current through the first electrothermal component to produce heating for generating force for moving the microcomponent.

37. The method according to claim 36, wherein the first electrothermal component is attached to a top side of the structural layer whereby the microcomponent moves in a direction toward the substrate when current is applied.

38. The method according to claim 37 further including removing the applied current, whereby the movable contact remains in contact with the stationary contact.

39. The method according to claim 36, wherein the first electrothermal component is attached to an underside of the structural layer whereby the microcomponent moves in a direction away from the substrate when current is applied.

40. The method according to claim 39 further including moving the movable contact from a position in contact with the stationary contact by removing the applied voltage and applying a current through the first electrothermal component, whereby heat is generated for deflecting the structural layer away from the substrate.

41. A method for fabricating a microscale switch, comprising:

(a) depositing a first conductive layer on a substrate;

(b) forming a stationary electrode and a stationary contact by removing a portion of the first conductive layer;

(c) depositing a sacrificial layer on the stationary electrode, the stationary contact, and the substrate;

(d) depositing a second conductive layer on the sacrificial layer;

(e) forming a movable electrode and a movable contact by removing a portion of the second conductive layer;

(f) depositing a structural layer on the movable electrode, the movable contact, and the sacrificial layer;

(g) depositing a third conductive layer on the structural layer;

(h) removing a portion of the third conductive layer to form an electrothermal component; and

(i) removing a sufficient amount of the sacrificial layer so as to define a first gap between the stationary electrode and the movable electrode, and to define a second gap between the stationary contact and the movable contact.

42. A method for fabricating a microscale switch, comprising:

(a) depositing a first conductive layer on a substrate;

(b) forming a stationary electrode and a stationary contact by removing a portion of the first conductive layer;

(c) depositing a sacrificial layer on the stationary electrode, the stationary contact, and the substrate;

(d) depositing a second conductive layer on the sacrificial layer;

(e) forming a movable electrode, a movable contact, and an electrothermal component by removing a portion of the second conductive layer;

(f) depositing a structural layer on the movable electrode, the movable contact, and the sacrificial layer; and

(g) removing a sufficient amount of the sacrificial layer so as to define a first gap between the stationary electrode and the movable electrode, and to define a second gap between the stationary contact and the movable contact.

43. A method for implementing a switching function in a microscale device having a movable microcomponent, comprising:

(a) applying a voltage between a movable electrode and a stationary electrode of the microscale device for electrostatically coupling the movable electrode with the stationary electrode, whereby the movable microcomponent is deflected and a movable contact moves into contact with a stationary contact to permit an electrical signal to pass through the movable and stationary contacts; and

(b) applying a current through a first electrothermal component of the microscale device to produce heating for generating force for moving the microcomponent.

44. The method according to claim 43, wherein the application of current to the first electrothermal component moves the movable contact into contact with the stationary contact.

45. The method according to claim 43, wherein the application of current to the first electrothermal component moves the movable contact in a direction away from the stationary contact.

46. The method according to claim 43 further including removing the applied current, wherein the applied voltage is sufficient to maintain the contact between the movable contact and the stationary contact.

47. The method according to claim 43 further including moving the movable contact from a position in contact with the stationary contact by removing the applied voltage and applying a current through the first electrothermal component, whereby heat is generated for deflecting the movable microcomponent away from the stationary contact.