MICROMECHANICAL RESONATOR

• US 20120091854A1
• Filed: 10/28/2011
• Published: 04/19/2012
• Est. Priority Date: 01/24/2008
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: VTI Technologies Oy (Murata Manufacturing Co Limited)
• Inventors: KAAJAKARI, Ville
• Granted Patent: US 8,334,736 B2
• Time in Patent Office: Days
• US Class Current: 310/309
• CPC Class Codes: H02N 1/008 Laterally driven motors, e.g. of the comb-drive type
• CPC Class Codes: H03H 2009/02299 Comb-like, i.e. the beam comprising a plurality of fingers or protrusions along its length
• CPC Class Codes: H03H 3/0076 for obtaining desired frequency or temperature coefficients
• CPC Class Codes: H03H 9/02275 Comb electrodes
• CPC Class Codes: H03H 9/02338 Suspension means
• CPC Class Codes: H03H 9/2463 Clamped-clamped beam resonators
• CPC Class Codes: H03H 9/2478 Single-Ended Tuning Fork resonators
• CPC Class Codes: H03H 9/2484 with two fork tines, e.g. Y-beam cantilever

Abstract

The invention relates to design of micromechanical resonators and, more precisely, to the design of microelectromechanical systems (MEMS) resonators. The invention provides an improved design structure for a microelectromechanical systems (MEMS) resonator including a movable mass structure and a spring structure. The spring structure includes a spring element. The spring element is anchored from one end and connected to a plurality of electrode fingers on another end. The plurality of electrode fingers are operatively connected together at the other end of the spring element. The improved structure is frequency robust to manufacturing variations and enables reliable frequency referencing with good performance, particularly in small size solutions.

Claims

1. A micromechanical resonator comprising:

a movable mass structure; and

a spring structure, comprising a spring element, the spring element anchored from one end and connected to a plurality of electrode fingers on another end, wherein the plurality of electrode fingers are operatively connected together at the other end of the spring element.

2. The micromechanical resonator according to claim 1, wherein the spring structure comprises two spring elements that are anchored together to form a tuning fork structure.

3. The micromechanical resonator of claim 1, wherein a width of the spring element is greater than the widths of the electrode fingers, the widths of the electrode fingers are dimensioned so that a sensitivity of a resonant frequency change with respect to dimensional manufacturing variations d(Δ

ω

₀/ω

₀)/dδ

approaches zero, wherein Δ

ω

₀/ω

₀ is a frequency change of a resonant frequency ω

₀and δ

is a dimension change.

4. The micromechanical resonator according to claim 1, wherein a width of the spring element is two to five times the widths of the electrode fingers.

5. The micromechanical resonator according to claim 1, wherein a width of the spring element is approximately three times the widths of the electrode fingers.

6. The micromechanical resonator according to any one of the claim 1, wherein resonant frequencies of the electrode fingers are two to five times higher than a resonant frequency of the micromechanical resonator.

7. The micromechanical resonator according to any one of the claim 1, wherein widths of the electrode fingers are dimensioned so that a slope of a resonant frequency change with respect to dimensional manufacturing variation change approaches zero at two or more locations.

8. The micromechanical resonator according to any one of the claim 1, wherein widths of the electrode fingers are configured so that a resonance frequency

9. The micromechanical resonator according to any one of the claim 1, wherein in dimensioning widths of the electrode fingers, an effect of bending of the electrode fingers is taken into account.

10. The micromechanical resonator according to any one of the claim 1, wherein lengths of the electrode fingers is dimensioned so that electrode finger resonant frequency affects a resonant frequency of the micromechanical resonator to generate a localized maximum of a micromechanical resonator resonant frequency change with respect to dimensional manufacturing variation change.

11. The micromechanical resonator according to claim 10, wherein lengths of the electrode fingers are ⅙

to ½

times a length of the spring element.

12. The micromechanical resonator according to any one of the claim 1, further comprising:

means for actuating the resonator electrostatically.

13. The micromechanical resonator according to any one of the claim 1, wherein the micromechanical resonator has a width of an electrode gap from 500 nm to 5 μ

m.

14. The micromechanical resonator according to claim 2, wherein the finger electrodes in the tuning fork structure are symmetrically arranged to those in another fork structure.

15. The micromechanical resonator according to claim 1, wherein the micromechanical resonator comprises a plurality of inter-digital electrodes for each of the pluralities of the finger electrodes.