Thermal arched beam microelectromechanical devices and associated fabrication methods

• US 5,994,816 A
• Filed: 09/24/1997
• Issued: 11/30/1999
• Est. Priority Date: 12/16/1996
• Status: Expired due to Term

• Current Assignee: Memscap Incorporated
• Original Assignee: MCNC, Inc.
• Inventors: Wood, Robert L., Mahadevan, Ramaswamy, Dhuler, Vijayakumar R.
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US08/936,598
• Time in Patent Office: 797 Days
• Field of Search: 310/306, 310/307, 310/309, 361/164
• US Class Current: 310/307
• CPC Class Codes: B81B 2201/031 Thermal actuators
• CPC Class Codes: B81B 2201/054 Microvalves
• CPC Class Codes: B81B 2203/0109 Bridges
• CPC Class Codes: B81B 2203/051 Translation according to an axis parallel to the substrate
• 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 3/0054 For holding or placing an element in a given position
• CPC Class Codes: F03G 7/06 using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like using thermal expansion of non-vaporising liquids F01K
• CPC Class Codes: F15C 5/00 Manufacture of fluid circuit elements; Manufacture of assemblages of such elements integrated circuits
• CPC Class Codes: F16K 2099/0071 with latching means
• CPC Class Codes: F16K 2099/0074 using photolithography, e.g. etching
• CPC Class Codes: F16K 2099/008 Multi-layer fabrications
• CPC Class Codes: F16K 99/0001 Microvalves microdevices B81B1/00; manufacture or treatment of devices or systems in or on a substrate B81C1/00; microfluidic structures B01L3/5027; micropumps F04B19/006
• CPC Class Codes: F16K 99/0011 Gate valves or sliding valves
• CPC Class Codes: F16K 99/0034 Operating means specially adapted for microvalves
• CPC Class Codes: F16K 99/0044 using thermo-electric means
• CPC Class Codes: G02B 6/3803 Adjustment or alignment devices for alignment prior to splicing
• CPC Class Codes: G02B 6/4226 Positioning means for moving the elements into alignment, e.g. alignment screws, deformation of the mount
• CPC Class Codes: H01H 1/0036 Switches making use of microelectromechanical systems [MEMS] for electromagnetic relays H01H50/005; for electrostatic relays H01H59/0009
• 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 2001/0047 operable only by mechanical latching
• CPC Class Codes: H01H 2001/0068 : with multi dimensional movement, i.e. the movable actuator performing movements in at least two different directions
• CPC Class Codes: H01H 2061/006 : Micromechanical thermal relay
• CPC Class Codes: H01H 61/00 : Electrothermal relays thermal switches not operated by electrical input, thermal switches with anticipating electrical input H01H37/00; thermally-sensitive members H01H37/32
• CPC Class Codes: H01H 61/02 : wherein the thermally-sensitive member is heated indirectly, e.g. resistively, inductively
• CPC Class Codes: H01H 67/26 : Co-ordinate-type selector switches not having relays at cross-points but involving mechanical movement, e.g. cross-bar switch, code-bar switch
• CPC Class Codes: H01H 9/14 : Adaptation for built-in safety spark gaps
• CPC Class Codes: Y10T 29/49105 : Switch making

Abstract

A MEMS actuator is provided that produces significant forces and displacements while consuming a reasonable amount of power. The MEMS actuator includes a microelectronic substrate, spaced apart supports on the substrate and a metallic arched beam extending between the spaced apart supports. The MEMS actuator also includes a heater for heating the arched beam to cause further arching of the beam. In order to effectively transfer heat from the heater to the metallic arched beam, the metallic arched beam extends over and is spaced, albeit slightly, from the heater. As such, the MEMS actuator effectively converts the heat generated by the heater into mechanical motion of the metallic arched beam. A family of other MEMS devices, such as relays, switching arrays and valves, are also provided that include one or more MEMS actuators in order to take advantage of its efficient operating characteristics. In addition, a method of fabricating a MEMS actuator is further provided.

Claims

1. A microelectromechanical relay comprising:

a microelectronic substrate;

a first pair of contacts on said microelectronic substrate; and

a first microelectromechanical actuator on said microelectronic substrate for controllably establishing electrical contact between said first pair of contacts, said first microelectromechanical actuator comprising;

spaced apart supports on said microelectronic substrate;

an arched beam extending between said spaced apart supports;

an actuator member operably coupled to said arched beam and extending outwardly therefrom toward said first pair of contacts; and

means for heating said arched beam to cause further arching of said beam such that said actuator member moves between an open position in which said actuator member is spaced from said first pair of contacts and a closed position in which said actuator member contacts said first pair of contacts and establishes an electrical connection therebetween.

2. A microelectromechanical relay according to claim 1 wherein said actuator member comprises:

a lengthwise extending portion coupled to said arched beam for movement therewith upon heating of said arched beam; and

an enlarged contact portion, responsive to movement of said lengthwise extending portion, for contacting said first pair of contacts.

3. A microelectromechanical relay according to claim 2 wherein said lengthwise extending portion and said enlarged contact portion of said actuator member are a unitary structure.

4. A microelectromechanical relay according to claim 2 wherein said lengthwise extending portion and said enlarged contact portion of said actuator member are separate structures, and wherein said lengthwise extending portion contacts said enlarged contact portion upon movement of said lengthwise extending portion in response to heating of said arched beam.

5. A microelectromechanical relay according to claim 1 further comprising means for holding said actuator member in position following heating of said arched beam and movement of said actuator member.

6. A microelectromechanical relay according to claim 5 wherein said means for holding said actuator member in position comprises means for applying an electrostatic force between said actuator member and said microelectronic substrate to thereby hold at least a portion of said actuator member against said microelectronic substrate.

7. A microelectromechanical relay according to claim 5 further comprising at least one retaining member on said microelectronic substrate and underlying said actuator member following movement of said actuator member in response to heating of said arched beam, wherein said actuator member includes a lower surface facing said microelectronic substrate that defines at least one recess for cooperably receiving a respective retaining member as said actuator member is held in position.

8. A microelectromechanical relay according to claim 1 further comprising latch means for latching the actuator member of the first microelectromechanical actuator following actuation thereof such that electrical contact is maintained between the first pair of contact members in the absence of further actuation.

9. A microelectromechanical relay according to claim 8 wherein said latch means comprises:

a projection extending outwardly from the actuator member of said first microelectromechanical actuator; and

a latch member for cooperably engaging the projection upon actuation of said first microelectromechanical actuator.

10. A microelectromechanical relay according to claim 9 further comprising reset means for unlatching the actuator member of the first microelectromechanical actuator such that electrical contact is no longer maintained between the first pair of contact members in the absence of further actuation of the first microelectromechanical actuator.

11. A microelectromechanical relay according to claim 10 wherein said reset means comprises a second microelectromechanical actuator having an actuator member that includes said latch member such that actuation of the second microelectromechanical actuator unlatches the actuator member of the first microelectromechanical actuator.

12. A microelectromechanical relay according to claim 1 wherein said heating means comprises means for externally heating said arched beam.

13. A microelectromechanical relay according to claim 1 further comprising a second microelectromechanical actuator on a portion of said microelectronic substrate opposite said first microelectromechanical actuator relative to said first pair of contacts, wherein said second microelectromechanical actuator controllably disengages said actuator member of said first microelectromechanical actuator from said first pair of contacts, and wherein said second microelectromechanical actuator comprises:

spaced apart supports on said microelectronic substrate;

an arched beam extending between said spaced apart supports;

an actuator member operably coupled to said arched beam and extending outwardly therefrom toward said first pair of contacts; and

means for heating said arched beam to cause further arching of said beam such that said actuator member contacts the actuator member of said first microelectromechanical actuator and disengages the actuator member of said first microelectromechanical actuator from said first pair of contacts.

14. A microelectromechanical relay according to claim 1 further comprising first and second field intensification structures electrically connected to respective ones of said first pair of contacts and disposed in a facing relationship to thereby define a discharge gap in order provide overvoltage protection.

15. A microelectromechanical relay according to claim 14 wherein each field intensification structure comprises at least one pointed projection extending toward the other field intensification structure to thereby define the discharge gap.

16. A microelectromechanical relay for alternately connecting first and second pairs of contacts, the microelectromechanical relay comprising:

a microelectronic substrate;

first and second pairs of contacts on said microelectronic substrate;

first and second microelectromechanical actuators on said microelectronic substrate, wherein each microelectromechanical actuator comprises;

spaced apart supports on said microelectronic substrate;

an arched beam extending between said spaced apart supports; and

an actuator member operably coupled to said arched beam and extending outwardly therefrom,

wherein said actuator member of said first microelectromechanical actuator cooperably engages said actuator member of said second microelectromechanical actuator upon actuation of said first microelectromechanical actuator such that electrical contact is established between said first pair of contacts if neither microelectromechanical actuator is actuated and such that electrical contact is established between said second pair of contacts if only said second microelectromechanical actuator is actuated.

17. A microelectromechanical relay according to claim 16 wherein the actuator member of said second microelectromechanical actuator includes an enlarged head portion disposed between said first and second pairs of contacts for alternately contacting said first and second pairs of contacts.

18. A microelectromechanical relay according to claim 16 wherein an end portion of the actuator member of said second microelectromechanical actuator comprises a sleeve opening through the end thereof, and wherein an end portion of the actuator member of said first microelectromechanical actuator comprises an engagement portion for insertion through the end of said sleeve upon actuation of said first microelectromechanical actuator such that the actuator members of said first and second microelectromechanical actuators remain cooperably engaged following deactuation of said first microelectromechanical actuator.

19. A microelectromechanical relay according to claim 16 wherein the arched beams of both said first and second microelectromechanical actuators are arched in the same direction.