Microelectromechanical systems having stored charge and methods for fabricating and using same

• US 7,456,042 B2
• Filed: 06/04/2006
• Issued: 11/25/2008
• 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
• Primary Examiner(s): Dang; Phuc T
• Application Number:
  US11/446,850
• Publication Number:
  US 20070281379A1
• Time in Patent Office: 905 Days
• Field of Search: 438/48, 438/50, 438/51, 438/53, 257/E21.192, 257/E21.247
• US Class Current: 438/50
• 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: H01L 2224/18 High density interconnect [HDI] connectors; Manufacturing methods related thereto

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; and

storing at least a portion of the electrical charge on the mechanical structure for a period of at least one day;

wherein the mechanical structure includes a first electrode disposed in the chamber, the micromechanical structure further includes a second electrode disposed in the chamber, and the method further includes supplying energy to cause relative movement between at least one portion of the first electrode and at least one portion of the second electrode.

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 the encapsulation structure comprises a semiconductor material.

6. The method of claim 1 wherein storing at least a portion of the electrical charge on the mechanical structure for a period of at least one day 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 storing at least a portion of the electrical charge on the mechanical structure for a period of at least one day 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 storing at least a portion of the electrical charge on the mechanical structure for a period of at least one day 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 includes supplying electrical charge to the first electrode; and

storing at least a portion of the electrical charge on the mechanical structure for a period of at least one day includes storing at least a portion of the electrical charge on the first electrode for a period of at least one day.

10. The method of claim 1 wherein supplying electrical charge to the mechanical structure includes supplying the mechanical structure with electrical charge from a thermionic electron source.

11. The method of claim 1 wherein the first electrode includes a movable mechanical structure and wherein supplying energy to cause relative movement between at least one portion of the first electrode and at least one portion of the second electrode includes supplying energy to cause movement of the movable mechanical structure.

12. The method of claim 11 wherein the movable mechanical structure includes a spring portion and a mass portion and wherein supplying energy to cause movement of the movable mechanical structure includes supplying energy to cause one or more portions of the movable mechanical structure to resonate at one or more resonant frequencies.

13. The method of claim 1 wherein supplying energy includes supplying vibrational energy to cause relative movement between the at least one portion of the first electrode and the at least one portion of the second electrode.

14. The method of claim 1 wherein the first electrode and the second electrode define a first capacitance having a magnitude that depends, at least in part, on a relative positioning of the at least one portion of the first electrode and the at least one portion of the second electrode.

15. The method of claim 1 further including converting at least a portion of the supplied energy to electrical energy.

16. The method of claim 15 further including supplying at least a portion of the electrical energy to at least one circuit or device.

17. The method of claim 16 wherein the at least one circuit or device includes a circuit having at least one device.

18. The method of claim 15 further including supplying at least a portion of the electrical energy to interface circuitry.

19. The method of claim 15 further including supplying at least a portion of the electrical energy to interface circuitry configured for wireless communication.

20. The method of claim 15 further including supplying at least a portion of the electrical energy to data processing electronics.

21. The method of claim 15 further including supplying at least a portion of the electrical energy to a sensor that senses a physical quantity and generates an electrical signal indicative thereof.

22. The method of claim 15 wherein converting at least a portion of the supplied energy to electrical energy includes generating an electrical signal, the method further including supplying the electrical signal to data processing electronics.

23. The method of claim 15 wherein converting at least a portion of the supplied energy to electrical energy comprises converting at least a portion of the supplied energy to an AC voltage or AC current.

24. The method of claim 15 further including using at least a portion of the electrical energy in powering at least one portion of at least one circuit or device.

25. The method of claim 24 wherein the at least one circuit or device is disposed in or on the electromechanical device.

26. The method of claim 24 wherein the at least one circuit or device is integrated in or on the electromechanical device.

27. The method of claim 24 wherein the at least one circuit or device is disposed in or on the substrate.

28. The method of claim 23 further including:

rectifying the AC voltage or AC current to provide a rectified voltage;

generating a regulated voltage from the rectified voltage; and

powering at least one circuit or device from the regulated voltage.

29. The method of claim 1 wherein storing at least a portion of the electrical charge on the mechanical structure for a period of at least one day comprises storing electrical charge on the mechanical structure for a period of at least one year.

30. The method of claim 1 wherein storing at least a portion of the electrical charge on the mechanical structure for a period of at least one day comprises storing at least a portion of the electrical charge on the mechanical structure for a period of at least ten years.

31. The method of claim 1 wherein storing at least a portion of the electrical charge on the mechanical structure for a period of at least one day includes storing at least 10 percent of the electrical charge on the mechanical structure for a period of at least one day.

32. The method of claim 1 wherein storing at least a portion of the electrical charge on the mechanical structure for a period of at least one day includes storing at least 50 percent of the electrical charge on the mechanical structure for a period of at least one day.

33. The method of claim 1 further 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; and

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

34. The method of claim 33 wherein storing at least a portion of the electrical charge on the mechanical structure includes storing at least a portion of the electrical charge on the mechanical structure after depositing the second encapsulation layer.

35. The method of claim 33 wherein the first encapsulation layer is comprised of a polycrystalline silicon, amorphous silicon, germanium, silicon/germanium or gallium arsenide.

36. The method of claim 33 wherein the second encapsulation layer is comprised of polycrystalline silicon, amorphous silicon, silicon carbide, silicon/germanium, germanium, or gallium arsenide.

37. The method of claim 9 wherein storing at least a portion of the electrical charge on the first electrode for a period of at least one day includes electrically isolating the first electrode such that at least a portion of the electrical charge is stored on the first electrode for a period of at least one day.