Annulus BAW Gyroscope Comb Drive for Wider Linear Actuation

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Solution Overview

Problem

Conventional MEMS resonators and gyroscopes face limitations in actuation range and fabrication imperfections, particularly in high-frequency applications, which affect their performance and accuracy in inertial measurement tasks.

Innovation Solution

The development of a substrate-decoupled annulus BAW pitch/roll gyroscope with a comb-drive element featuring tapered comb fingers and slanted sidewall electrodes, which provides a larger linear drive range and reduces mechanical nonlinearity, enabling mode-matched operation and improved quadrature error cancellation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional MEMS resonators are used, then fabrication is simpler, but actuation range is limited and mechanical nonlinearity increases

Engineering Contradiction:

Improvefabrication simplicityVSAvoidactuation range

Core Design Contradiction:

Ease of manufactureVSEase of operation

Solution Approach 1:

The resonator is segmented into a drive mode annulus and a sense mode annulus, allowing independent optimization of each mode's characteristics. This segmentation enables the drive mode to operate at larger amplitudes while the sense mode maintains high sensitivity, resolving the contradiction between ease of manufacture and actuation range.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from planar electrode configurations to three-dimensional slanted electrodes positioned above the resonator perimeter. This dimensional change enables larger actuation forces and extended linear drive range without complicating the fundamental fabrication process, as the slanted electrodes can be formed using standard deposition and etching techniques.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Device complexity

If conventional comb-drive elements are used, then device complexity is lower, but linear drive range is limited

Engineering Contradiction:

Improvecomb-drive structureVSAvoidlinear drive range

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

The comb fingers are given curved or tapered geometries rather than straight rectangular shapes. This curvature optimization increases the overlapping area between drive and sense comb fingers, enhancing the electrostatic coupling and extending the linear drive range while maintaining a relatively simple comb-drive structure that can be fabricated using standard MEMS processes.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Speed

If high-frequency operation is implemented, then resonator performance improves, but mechanical nonlinearity increases

Engineering Contradiction:

Improveresonance frequencyVSAvoidmechanical nonlinearity

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The invention optimizes geometric parameters including the thickness, width, and spacing of the annular resonators and comb fingers. By carefully controlling these parameters, the resonator can operate at high frequencies while maintaining linear mechanical behavior. The slanted electrode geometry further contributes to reducing mechanical nonlinearity by distributing stress more evenly across the structure.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design achieves higher actuation forces and larger drive amplitudes, enhancing the performance of BAW resonators by increasing the linear drive range and reducing noise, thereby improving the accuracy and reliability of inertial measurements.

Implementation Method 1

The comb-drive element includes first comb fingers protruding from the resonator member, and second comb fingers interdigitated with the first comb fingers to define sub-micron capacitive gaps therebetween

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Implementation Method 2

Bulk acoustic wave (BAW) refers to a mode of vibration that extends throughout a bulk portion of a resonator element or member

Methodology Applied

Scientific EffectBulk acoustic wave: Sound

Implementation Method 3

substrate-decoupled annulus BAW pitch/roll gyroscope

Methodology Applied

Scientific EffectCoriolis force: Coriolis Force

Data Source

PatentUS11566898B2Comb-driven substrate decoupled annulus pitch/roll BAW gyroscope with slanted quadrature tuning electrode

Publication Date: 2023.01.31 GEORGIA TECH RES CORP

AI summary

A bulk acoustic wave resonator apparatus includes a resonator member, at least one anchor structure coupling the resonator member to a substrate, and a comb-drive element connected to the resonator member. The comb-drive element includes first comb fingers protruding from the resonator member, and second comb fingers of a different material than the first comb fingers interdigitated with the first comb fingers to define sub-micron capacitive gaps therebetween. Respective sidewalls of the first comb fingers are oppositely-tapered relative to respective sidewalls of the second comb fingers along respective lengths thereof, such that operation of the comb-drive element varies the sub-micron capacitive gaps at the respective sidewalls thereof. Respective tuning electrodes, which are slanted at respective angles parallel to an angle of respective sidewalls of the resonator member, may also be provided for quadrature tuning between different resonance modes of the resonator member. Related devices and fabrication methods are also discussed.