Microstructure with Enlarged Mass and Electrode Area for Kinetic to Electrical Energy Conversion

• US 20090140443A1
• Filed: 11/26/2008
• Published: 06/04/2009
• Est. Priority Date: 11/29/2007
• Status: Active Grant

• Current Assignee: Stichting Imec Nederland
• Original Assignee: Stichting Imec Nederland
• Inventors: Goedbloed, Martijn, Hohlfeld, Dennis
• Granted Patent: US 7,880,246 B2
• Time in Patent Office: Days
• US Class Current: 257/786
• 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: H02N 1/08 with conductive charge carrier, i.e. capacitor machines

Abstract

A microstructure has a substrate, a fixed electrode having a plurality of fixed fingers fixed to the substrate, a movable electrode having a body (28) and a plurality of fingers (22) extending from the body, the movable electrode being movable relative to the fixed fingers to vary a capacitance of the electrodes. The fixed fingers (21) extend in a first plane parallel to a main surface of the substrate, wherein the body of the movable electrode extends in a second plane adjacent to the first plane so that the body faces at least some of the plurality of fixed fingers. Such vertical integration can help enable such devices to be made more compact.

Claims

1. A microstructure comprising:

a substrate;

a fixed electrode having a plurality of fixed fingers fixed to the substrate;

a movable electrode having a body and a plurality of fingers extending from the body, the movable electrode being movable relative to the fixed fingers to vary a capacitance of the electrodes;

wherein the plurality of fixed fingers extend in a first plane parallel to a main surface of the substrate and the body of the movable electrode extends in a second plane adjacent to the first plane so that the body faces at least some of the plurality of fixed fingers.

2. The microstructure of claim 1, wherein the plurality of fixed fingers is suspended between fixation structures anchored to the substrate.

3. The microstructure according to claim 1, wherein the plurality of fixed fingers extends from an edge of the microstructure to an opposite edge of the microstructure.

4. The microstructure according to claim 1, wherein the fixed fingers and the fingers of the movable electrode are interdigitated.

5. The microstructure according to claim 1, the body comprising a seismic mass.

6. The microstructure according to claim 1, further comprising means for tuning a resonance frequency of the microstructure.

7. The microstructure according to claim 6, the means for tuning the resonance frequency comprising at least one electrostatic tuning actuator.

8. The microstructure according to claim 7, the at least one electrostatic tuning actuator comprising a plurality of movable tuning fingers and a plurality of fixed tuning fingers, the plurality of fixed tuning fingers having a linearly varying length, the plurality of movable tuning fingers and the plurality of fixed tuning fingers being interdigitated.

9. The microstructure according to claim 6, wherein the means for tuning the resonance frequency is vertically integrated with said body.

10. An electrostatic scavenger comprising:

a substrate;

a fixed electrode having a plurality of fixed fingers fixed to the substrate;

a movable electrode having a body and a plurality of fingers extending from the body, the movable electrode being movable relative to the fixed fingers to vary a capacitance of the electrodes;

wherein the plurality of fixed fingers extend in a first plane parallel to a main surface of the substrate and the body of the movable electrode extends in a second plane adjacent to the first plane so that the body faces at least some of the plurality of fixed fingers.

11. A method of manufacturing a microstructure, the method comprising:

providing on the substrate a plurality of first beam-shaped elements for forming the fingers of the movable electrode;

providing a plurality of second beam-shaped elements for forming the plurality of fixed fingers, a height of the plurality of second beam-shaped elements being smaller than a height of the plurality of first beam-shaped elements;

providing the body in the second plane to physically connect the plurality of first beam-shaped elements; and

releasing the plurality of first beam-shaped elements and the body to make them movable relative to the plurality of second beam-shaped elements.

12. The method according to claim 11, wherein the substrate comprises an SOI substrate comprising a handling layer, an intermediate silicon oxide layer and a functional silicon layer.

13. The method according to claim 12, wherein providing a plurality of first beam-shaped elements on the substrate comprises forming the plurality of first beam-shaped elements in the functional silicon layer by etching through the functional silicon layer.

14. The method according to claim 12, wherein providing a plurality of second beam-shaped elements comprises forming the plurality of second beam-shaped elements in the functional silicon layer by etching through the functional silicon layer.

15. The method according to claim 12, further comprising partly etching the plurality of second beam-shaped elements for reducing their height.

16. The method according to claim 12, wherein providing the body comprises bonding a capping wafer to the plurality of first beam-shaped elements.

17. The method according to claim 12, wherein releasing the plurality of first beam-shaped elements comprises removing the intermediate silicon oxide layer between the handling layer and the plurality of first beam-shaped elements and wherein releasing the body comprises structuring the body by etching.

18. The method according to claim 11, wherein providing on the substrate a plurality of first beam-shaped elements comprises:

providing on the substrate a plurality of shallow beam-shaped features at locations where the plurality of first beam-shaped elements are to be formed;

bonding a capping wafer to the substrate; and

forming the plurality of first beam-shaped elements in the capping wafer where the shallow beam-shaped features are located, by etching through the capping wafer.

19. The method according to claim 18, wherein providing the plurality of second beam-shaped elements comprises etching through the capping wafer.

20. The method according to claim 18, wherein providing the body comprises using at least part of the substrate as the body.

21. The method according to claim 18, wherein releasing the plurality of first beam-shaped elements and releasing the body comprise etching through the substrate.