Methods for trapping charge in a microelectromechanical system and microelectromechanical system employing same

• US 20070281387A1
• Filed: 06/04/2006
• Published: 12/06/2007
• Est. Priority Date: 06/04/2006
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Stark, Brian H., Partridge, Aaron, Lutz, Markus
• Granted Patent: US 7,824,943 B2
• Time in Patent Office: Days
• US Class Current: 438/106
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: B81B 3/0086 Electrical characteristics, e.g. reducing driving voltage, improving resistance to peak voltage
• CPC Class Codes: H01H 85/04 Fuses, i.e. expendable parts of the protective device, e.g. cartridges

Abstract

Many inventions are disclosed. Some aspects are directed to MEMS, and/or methods for use with and/or for fabricating MEMS, that supply, store, and/or trap charge on a mechanical structure disposed in a chamber. Various structures may be disposed in the chamber and employed in supplying, storing and/or trapping charge on the mechanical structure. In some aspects, a breakable link, a thermionic electron source and/or a movable mechanical structure are employed. The breakable link may comprise a fuse. In one embodiment, the movable mechanical structure is driven to resonate. In some aspects, the electrical charge enables a transducer to convert vibrational energy to electrical energy, which may be used to power circuit(s), device(s) and/or other purpose(s). In some aspects, the electrical charge is employed in changing the resonant frequency of a mechanical structure and/or generating an electrostatic force, which may be repulsive.

Claims

1. A method for use in association with an electromechanical device having a substrate and an encapsulation structure, the encapsulation structure being disposed over at least a portion of the substrate and defining at least a portion of a chamber, the electromechanical device further having a micromechanical structure that includes a mechanical structure disposed in the chamber, the method comprising:

supplying electrical charge to the mechanical structure of the micromechanical structure through an electrical connection disposed in the chamber; and

electrically isolating the mechanical structure, wherein electrically isolating the mechanical structure includes breaking the electrical connection.

2. The method of claim 1 wherein the micromechanical structure comprises a micromachined mechanical structure.

3. The method of claim 1 wherein the mechanical structure comprises a semiconductor material.

4. The method of claim 3 wherein the semiconductor material is comprised of polycrystalline silicon, amorphous silicon, silicon carbide, silicon/germanium, germanium, or gallium arsenide.

5. The method of claim 1 wherein electrically isolating the mechanical structure includes electrically isolating the mechanical structure such that at least a portion of the electrical charge is stored on the mechanical structure for a period of at least one day.

6. The method of claim 1 wherein electrically isolating the mechanical structure includes electrically isolating the mechanical structure such that at least a portion of the electrical charge will be stored on the mechanical structure for a period of at least one month.

7. The method of claim 1 wherein electrically isolating the mechanical structure includes electrically isolating the mechanical structure such that at least a portion of the electrical charge will be stored on the mechanical structure for a period of at least one year.

8. The method of claim 1 wherein electrically isolating the mechanical structure includes electrically isolating the mechanical structure such that at least a portion of the electrical charge will be stored on the mechanical structure for a period of at least ten years.

9. The method of claim 1 wherein supplying electrical charge to the mechanical structure through an electrical connection disposed in the chamber includes supplying electrical charge to the mechanical structure through an electrical connection between the mechanical structure and another mechanical structure disposed in the chamber.

10. The method of claim 1 wherein electrically isolating the mechanical structure includes irreversibly breaking the electrical connection.

11. The method of claim 1 wherein supplying electrical charge to the mechanical structure through an electrical connection disposed in the chamber includes supplying electrical charge to the mechanical structure through a fuse disposed in the chamber.

12. The method of claim 11 wherein breaking the electrical connection includes blowing at least one portion of the fuse.

13. The method of claim 12 wherein blowing at least one portion of the fuse includes melting at least one portion of the fuse.

14. The method of claim 12 wherein blowing at least one portion of the fuse includes supplying at least one portion of the fuse with electrical current to heat the at least one portion of the fuse.

15. The method of claim 12 wherein blowing at least one portion of the fuse includes supplying at least one portion of the fuse with electrical current to cause the at least one portion of the fuse to dissipate energy and reach or exceed a temperature at which the at least one portion of the fuse blows.

16. The method of claim 12 wherein the micromechanical structure further includes a first electrode and a second electrode each disposed in the chamber, the fuse includes a first portion and a second portion, the first portion having a first end coupled to the first electrode and a second end coupled to the second electrode, the second portion having a first end coupled to the first portion of the fuse and a second end coupled to the mechanical structure, and wherein blowing at least one portion of the fuse includes blowing at least one portion of the first portion of the fuse and blowing at least one portion of the second portion of the fuse.

17. The method of claim 1 wherein supplying electrical charge to the mechanical structure through an electrical connection disposed in the chamber includes supplying electrical charge to the mechanical structure through an electrical connection that includes at least one portion of at least one movable structure disposed in the chamber.

18. The method of claim 17 wherein supplying electrical charge to the mechanical structure through an electrical connection disposed in the chamber includes moving at least one portion of the at least one movable structure disposed in the chamber to provide electrical contact between a first contact surface and a second contact surface.

19. The method of claim 18 wherein moving at least one portion of the at least one movable structure disposed in the chamber to provide electrical contact between a first contact surface and a second contact surface includes controlling the at least one portion of the at least one movable structure to provide electrical contact between the first contact surface and the second contact surface.

20. The method of claim 19 wherein controlling the at least one portion of the at least one movable structure to provide electrical contact between the first contact surface and the second contact surface includes providing at least one electrical signal that causes at least one electrostatic force that causes the at least one portion of the at least one movable structure to move and provide electrical contact between the first contact surface and the second contact surface.

21. The method of claim 19 wherein controlling the at least one portion of the at least one movable structure to provide electrical contact between the first contact surface and the second contact surface includes controlling the at least one portion of the at least one movable structure to provide electrical contact between a contact surface of the at least one portion of the at least one movable structure and a contact surface of the mechanical structure.

22. The method of claim 19 wherein controlling the at least one portion of the at least one movable structure to provide electrical contact between the first contact surface and the second contact surface includes driving the at least one portion of the at least one movable structure into mechanical resonance.

23. The method of claim 22 wherein driving the at least one portion of the at least one movable structure into mechanical resonance includes providing at least one electrical signal that causes at least one electrostatic force that causes the at least one portion of the at least one movable structure to resonate at one or more frequencies.

24. The method of claim 22 wherein driving the at least one portion of the at least one movable structure into mechanical resonance includes driving the at least one portion of the at least one movable structure into mechanical resonance, the first contact surface making electrical contact with the second contact surface during a portion of the mechanical resonance.

25. The method of claim 24 wherein driving the at least one portion of the at least one movable structure into mechanical resonance includes driving the at least one portion of the at least one movable structure into mechanical resonance, the first contact surface not making electrical contact with the second contact surface during a portion of the mechanical resonance.

26. A method for use in association with an electromechanical device having a mechanical structure, the method comprising:

depositing a sacrificial layer over the mechanical structure;

depositing a first encapsulation layer over the sacrificial layer;

forming at least one vent through the first encapsulation layer to allow removal of at least a portion of the sacrificial layer;

removing at least a portion of the sacrificial layer to form the chamber;

depositing a second encapsulation layer over or in the vent to seal the chamber;

supplying electrical charge to at least one portion of the mechanical structure through an electrical connection disposed in the chamber; and

electrically isolating the at least one portion of the mechanical structure.

27. The method of claim 26 wherein the mechanical structure comprises a semiconductor material.

28. The method of claim 26 wherein the first encapsulation layer comprises a semiconductor material.

29. The method of claim 26 wherein the second encapsulation layer comprises a semiconductor material.

30. A method for use in association with an electromechanical device having a substrate and an encapsulation structure, the encapsulation structure being disposed over at least a portion of the substrate and defining at least a portion of a chamber, the electromechanical device further having a micromechanical structure that includes a mechanical structure disposed in the chamber, the method comprising:

supplying electrical charge to the mechanical structure of the micromechanical structure through a breakable link disposed in the chamber; and

irreversibly breaking at least a portion of the breakable link.

31. The method of claim 30 wherein the mechanical structure comprises a semiconductor material.

32. The method of claim 30 wherein supplying electrical charge to the mechanical structure through a breakable link includes supplying electrical charge to the mechanical structure through a fuse disposed in the chamber.

33. The method of claim 32 wherein irreversibly breaking at least one portion of the breakable link includes blowing at least one portion of the fuse.

34. A method for use in association with an electromechanical device having a substrate and an encapsulation structure, the encapsulation structure being disposed over at least a portion of the substrate and defining at least a portion of a chamber, the electromechanical device further having a micromechanical structure that includes a mechanical structure disposed in the chamber, the method comprising:

controlling at least one portion of at least one movable mechanical structure disposed in the chamber to provide an electrical connection;

supplying electrical charge to the mechanical structure of the micromechanical structure through the electrical connection; and

breaking the electrical connection.

35. The method of claim 34 wherein the mechanical structure comprises a semiconductor material.

36. The method of claim 34 wherein controlling at least one portion of at least one movable mechanical structure disposed in the chamber to provide an electrical connection includes controlling at least one portion of the at least one movable structure to provide electrical contact between a first contact surface and a second contact surface.

37. The method of claim 34 wherein controlling at least one portion of at least one movable mechanical structure disposed in the chamber to provide an electrical connection includes driving at least one portion of the at least one movable structure into mechanical resonance.