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

• US 7,824,943 B2
• Filed: 06/04/2006
• Issued: 11/02/2010
• Est. Priority Date: 06/04/2006
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Akustica Incorporated
• Inventors: Lutz, Markus, Stark, Brian H., Partridge, Aaron
• Primary Examiner(s): Garber; Charles D
• Assistant Examiner(s): SENE, PAPE A
• Application Number:
  US11/446,851
• Publication Number:
  US 20070281387A1
• Time in Patent Office: 1,612 Days
• Field of Search: 438 48- 52
• US Class Current: 438/48
• 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 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 while the at least one portion of the mechanical structure remains charged;

wherein;

electrically isolating the mechanical structure includes irreversibly breaking the electrical connection;

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;

breaking the electrical connection includes blowing at least one portion of the fuse; and

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.

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

3. The method of claim 1 wherein the first encapsulation layer comprises a semiconductor material.

4. The method of claim 1 wherein the second encapsulation layer comprises a semiconductor material.

5. The method of claim 2 wherein the semiconductor material of the mechanical structure is comprised of polycrystalline silicon, amorphous silicon, silicon carbide, silicon/germanium, germanium, or gallium arsenide.

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 is stored on the mechanical structure for a period of at least one day.

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 month.

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 one year.

9. 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.

10. The method of claim 1 wherein supplying electrical charge to the mechanical structure through the 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.

11. The method of claim 1 wherein blowing at least one portion of the fuse includes melting at least one portion of the fuse.

12. The method of claim 1 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.

13. The method of claim 1 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.

14. The method of claim 1 wherein the electrical isolation of the at least one portion of the mechanical structure is from the electrical connection.