Substrate-Supported Shear Resonator Structure for Acoustic Energy Confinement
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Solution Overview
Problem
Conventional piezoelectric resonators with single thickness shear mode designs suffer from energy leakage to inactive substrate areas, leading to reduced detection sensitivity and performance due to external circuit requirements for environmental compensation and increased spurious modes.
Innovation Solution
The implementation of dual thickness shear mode resonators with contoured shapes and isolation regions, supported by posts and caps, to confine acoustic energy and reduce energy leakage, enhancing the quality factor and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the resonator uses a single thickness shear mode design with planar surfaces, then the device structure is simple, but energy leakage occurs from the active section to the surrounding inactive substrate area, reducing detection sensitivity
Solution Approach 1:
The resonator structure is divided into distinct active and inactive regions separated by isolation regions. The active region contains the piezoelectric crystal with electrodes, while the inactive region is isolated by trenches or isolation structures, preventing energy leakage between regions and improving detection sensitivity.
Solution Approach 2:
Different regions of the resonator are given different properties: the active region has piezoelectric material with specific crystal orientation for shear mode operation, while the inactive region is isolated or modified to prevent energy propagation. This local differentiation confines acoustic energy to where it is needed.
2Reliability
If external circuit components are used to compensate environmental effects for stable operation, then operational stability is improved, but response time increases due to compensation delays
Solution Approach 1:
The resonator design incorporates inherent compensation mechanisms through its structure. The isolation regions and controlled substrate connection provide automatic stabilization of acoustic energy confinement without requiring external circuit compensation, thus maintaining operational stability while reducing response time.
3Ease of manufacture
If the resonator is directly connected to the substrate, then manufacturing is simplified, but energy leakage to the surrounding substrate area increases, limiting shear displacement
Solution Approach 1:
The isolation regions are created by removing substrate material (via trenches or etching) in the areas surrounding the active region. This extraction of substrate material prevents energy leakage paths while maintaining the connection between the resonator and substrate through controlled regions, thereby improving detection sensitivity without complicating manufacturing.
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 configuration effectively minimizes energy leakage, increases the quality factor, and improves detection sensitivity by confining acoustic energy within the active region, thereby enhancing the performance of the resonator.
Implementation Method 1
The thickness shear mode is excited when an electric field is applied in the direction of thickness to a piezoelectric crystal 20 giving a shear deformation (dashed line) to the piezoelectric crystal 20
Implementation Method 2
The implementation of dual thickness shear mode resonators with contoured shapes and isolation regions, supported by posts and caps, to confine acoustic energy and reduce energy leakage
Implementation Method 3
One acoustic mode for resonators is the Thickness Shear Mode (TSM). In prior art designs, these TSM based resonators are single mode device, i.e., their operational principle is on the excitation of slow thickness-shear mode
Data Source
AI summary
A sensor that includes a substrate with a first side having a cavity extending into the first side. A resonator is connected to the substrate and extends over the cavity with the resonator including first and second electrodes overlapping on opposing sides of the piezoelectric crystal. The substrate is connected to the resonator such that one or more physical parameters exerted on the substrate are transferred to the resonator.