Fused Quartz Dual-Shell Resonator for Shock-Stable Gyroscopes
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Solution Overview
Problem
Conventional MEMS gyroscope resonators face mechanical stress issues and microcracks in harsh dynamic environments, leading to reduced dynamic pull-in stability and snap-down of resonant structures due to limited bonding surfaces and weak points.
Innovation Solution
A dual-shell resonator structure with a co-fabricated outer cap shell and inner device shell, sharing a common stem, formed by triple-stacked wafers with concentric cavities, using high-temperature glassblowing and plasma-assisted wafer bonding, and featuring a hemispherical dome configuration to enhance structural rigidity and shock survivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional resonator structures are used, then manufacturing is simpler, but shock survivability and structural integrity deteriorate due to microcracks and fracture in high-stress locations
Solution Approach 1:
The resonator is divided into two separate shells: an outer cap shell and an inner device shell. This segmentation allows each shell to be optimized independently for its specific function while distributing mechanical stress across multiple structures, preventing microcracks and fracture in high-stress locations during shock events.
Solution Approach 2:
The inner device shell is nested within the outer cap shell, creating a protective configuration where the outer shell serves as a protective enclosure. This nested arrangement provides structural reinforcement and isolates the sensitive inner resonant structure from external mechanical shocks and environmental factors.
2Stability of the object's composition
If limited bonding surfaces are used, then device complexity is reduced, but dynamic pull-in stability deteriorates due to weak bonding points
Solution Approach 1:
The bonding structure extends from a single-point or limited-surface connection to a distributed three-dimensional anchor system. The stem structure provides multiple bonding interfaces distributed throughout the volume, increasing the effective bonding surface area and distributing mechanical loads across multiple attachment points, thereby enhancing dynamic pull-in stability.
3Object-affected harmful factors
If conventional single-shell structure is used, then manufacturing process is simpler, but vibration sensitivity increases leading to snap-down of resonant structure
Solution Approach 1:
The outer cap shell acts as a pre-configured protective cushion that absorbs and dissipates external vibration and shock energy before it reaches the inner resonant structure. This protective enclosure prevents snap-down of the resonant structure during high-g shock events by providing mechanical buffering.
4Strength
If triple-stacked wafers with concentric cavities are used, then structural rigidity is improved, but manufacturing precision requirements increase
Solution Approach 1:
Multiple functional features are merged into the triple-stacked wafer structure: the outer cap shell, inner device shell, and common stem are all formed from three stacked wafers with concentric cavities. This integration achieves high structural rigidity while maintaining manufacturability through a unified fabrication process that creates self-aligned structures.
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
The dual-shell resonator design improves shock survivability and reduces vibration sensitivity by providing a fixed-fixed anchor for shell attachment, maintaining structural integrity and enabling operation through high-g-shock and vibration, while maintaining a high mechanical quality factor to minimize noise.
Implementation Method 1
The outer cap shell, inner device shell and common stem are formed by triple stacked wafers with concentric cavities
Implementation Method 2
using high-temperature glassblowing and plasma-assisted wafer bonding
Data Source
AI summary
A dual-shell architecture and methods of fabrication of fused quartz resonators is disclosed. The architecture may include two encapsulated and concentric cavities using plasma-activated wafer bonding followed by the high-temperature glassblowing. The dual-shell architecture can provide a protective shield as well as a “fixed-fixed” anchor for the sensing element of the resonators. Structures can be instrumented to operate as a resonator, a gyroscope, or other vibratory sensor and for precision operation in a harsh environment. Methods for fabricating a dual-shell resonator structure can include pre-etching cavities on a cap wafer, pre-etching cavities on a device wafer, bonding the device wafer to a substrate wafer to form a substrate pair and aligning and bonding the cap wafer to the substrate pair to form a wafer stack with aligned cavities including a cap cavity and a device cavity. The wafer stack may be glassblown to form a dual-shell structure.