# US 8,334,736 B2 · Micromechanical resonator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,334,736 B2 - Document ID: US8334736B2 - Status: Granted - Kind: B2 - Application number: 13/284,196 - Filed: 2011-10-28 - Published: 2012-04-19 - Granted: 2012-12-18 - Earliest claimed: 2008-01-24 - Assignees: Murata Electronics Oy - Inventors: Ville Kaajakari - Web page: https://patentgrep.com/patent/US8334736B2 ## CPC - H03H 9/2463: {Clamped-clamped beam resonators} - H02N 1/008: {Laterally driven motors, e.g. of the comb-drive type} - H03H 3/0076: {for obtaining desired frequency or temperature coefficients} - H03H 9/02275: {Comb electrodes} - H03H 9/02338: {Suspension means} - H03H 9/2478: {Single-Ended Tuning Fork resonators} - H03H 9/2484: {with two fork tines, e.g. Y-beam cantilever} - H03H 2009/02299: {Comb-like, i.e. the beam comprising a plurality of fingers or protrusions along its length} - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H02N: ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR ## 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 ### Claim 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 only at the other end of the spring element, wherein the plurality of electrode fingers extend parallel to the spring element. ### Claim 2 (depends on 1) 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. ### Claim 3 (depends on 2) The micromechanical resonator according to claim 2, wherein the finger electrodes connected to one of the two spring elements in the tuning fork structure are symmetrically arranged to those connected to the other of the two spring elements in the tuning fork structure. ### Claim 4 (depends on 1) 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(Δω0/ω0)/dδ approaches zero, wherein Δω0/ω0 is a frequency change of a resonant frequency ω0 and δ is a dimension change. ### Claim 5 (depends on 1) 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. ### Claim 6 (depends on 1) The micromechanical resonator according to claim 1, wherein a width of the spring element is approximately three times the widths of the electrode fingers. ### Claim 7 (depends on 1) The micromechanical resonator according to claim 1, further comprising: means for actuating the resonator electrostatically. ### Claim 8 (depends on 1) The micromechanical resonator according to claim 1, wherein the micromechanical resonator has a width of an electrode gap from 500 nm to 5 μm. ### Claim 9 (depends on 1) 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. ### Claim 10 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, wherein resonant frequencies of the electrode fingers are two to five times higher than a resonant frequency of the micromechanical resonator. ### Claim 11 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, 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. ### Claim 12 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, wherein widths of the electrode fingers are configured so that a resonance frequency ω f = 0.8 ⁢ Y ρ ⁢ w f L f 2 of each of the electrode fingers is taken into account, wherein wf is an electrode finger width, Lf is an electrode finger length, ρ is a density, and Y is Young's modulus. ### Claim 13 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, wherein in dimensioning widths of the electrode fingers, an effect of bending of the electrode fingers is taken into account. ### Claim 14 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, wherein lengths of the electrode fingers are 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. ### Claim 15 (depends on 14) The micromechanical resonator according to claim 14, wherein lengths of the electrode fingers are ⅙ to ½ times a length of the spring element.