Multiple coil spring MEMS resonator

• US 9,866,200 B2
• Filed: 10/14/2015
• Issued: 01/09/2018
• Est. Priority Date: 10/22/2014
• Status: Active Grant

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Microchip Technology Incorporated
• Inventors: Hsu, Wan-Thai, Clark, John Ryan
• Primary Examiner(s): Summons, Barbara
• Application Number:
  US14/883,400
• Publication Number:
  US 20160118955A1
• Time in Patent Office: 818 Days
• Field of Search: 333186
• CPC Class Codes: B81B 2201/0271 Resonators; ultrasonic resonators
• CPC Class Codes: H03H 2009/02251 Design
• CPC Class Codes: H03H 2009/02283 Vibrating means
• CPC Class Codes: H03H 2009/02307 Dog-bone-like structure, i.e. the elongated part of the "bone" is doubly clamped
• CPC Class Codes: H03H 2009/0233 comprising perforations
• CPC Class Codes: H03H 2009/02346 Anchors for ring resonators
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 9/02244 of microelectro-mechanical resonators
• CPC Class Codes: H03H 9/02259 Driving or detection means
• CPC Class Codes: H03H 9/02338 Suspension means
• CPC Class Codes: H03H 9/2431 Ring resonators
• CPC Class Codes: H03H 9/2452 Free-free beam resonators

Abstract

A multiple coil spring MEMS resonator includes a center anchor and a resonator body including two or more coil springs extending in a spiral pattern from the center anchor to an outer closed ring. Each pair of coil springs originates from opposing points on the center anchor and extends in the spiral pattern to opposing points on the outer ring. The number of coil springs, the length and the width of the coil springs and the weight of the outer ring are selected to realize a desired resonant frequency.

Claims

1. A MEMS (microelectromechanical systems) resonator comprising:

a center anchor connected to a substrate;

a resonator body comprising one or more pairs of coil springs and an outer closed ring suspended above the substrate, the coil springs extending in a spiral pattern from the center anchor to the outer closed ring, the center anchor is at a nodal point of the resonator body;

one or more transducers formed on the outer closed ring, each transducer being formed perpendicular to and extending outward from the outer closed ring;

a set of drive electrodes and a set of sense electrodes formed attached to the substrate, each transducer being capacitively coupled to one drive electrode and one sense electrode, a pair of the drive and sense electrodes being coupled to drive a respective transducer using electrostatic parallel plate drive, the drive and sense electrodes and the respective transducer being capacitivly coupled in a parallel plate configuration and each of the drive and sense electrodes being separated from the respective transducer by a narrow gap in the parallel plate configuration.

2. The MEMS resonator of claim 1, wherein a number of the pairs of coil springs, a length and a width of the coil springs, and a weight of the outer closed ring are selected to tune a resonant frequency of the MEMS resonator.

3. The MEMS resonator of claim 2, further comprising:

structures formed on the outer closed ring to adjust the weight of the outer closed ring.

4. The MEMS resonator of claim 1, wherein a respective drive electrode and a respective transducer are separated by a first gap, and a respective sense electrode and a respective transducer are separated by a second gap, each of the first and second gaps being equal to or less than 1 μ

m.

5. The MEMS resonator of claim 1, wherein the resonator body has a thickness of 20-30 μ

m.

6. The MEMS resonator of claim 1, wherein the resonator body is formed from a material selected from a single crystalline silicon layer and a polycrystalline silicon layer.

7. The MEMS resonator of claim 1, wherein the substrate comprises a silicon base layer on which an insulating layer is formed.

8. The MEMS resonator of claim 1, wherein each of the coil springs originates from a first position on the center anchor and extends in a spiral pattern for a full circle around the center anchor to terminate on the outer closed ring at a position aligned with the first position.

9. The MEMS resonator of claim 1, wherein individual coil springs of each pair of coil springs originate from opposing points on the center anchor and extend in a spiral pattern to opposing points on the outer closed ring.

10. The MEMS resonator of claim 1, wherein each of the coil springs extends in a clockwise spiral pattern from the center anchor.

11. The MEMS resonator of claim 1, wherein each of the coil springs extends in a counter-clockwise spiral pattern from the center anchor.

12. The MEMS resonator of claim 1, wherein the outer closed ring comprises release holes formed therein, the release holes adjusting the weight of the outer closed ring.

13. The MEMS resonator of claim 1, wherein the one or more transducers comprise release holes formed therein, the release holes adjusting the weight of the one or more transducers.

14. The MEMS resonator of claim 1, wherein the one or more transducers includes a plurality of transducers, the plurality of transducers being driven by respective drive electrodes by a DC voltage and AC drive signals in different phases.