Shear Wave Piezoelectric Resonator with Slanted Cavity Structure
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Solution Overview
Problem
Existing thin-film bulk acoustic resonators face challenges in manufacturing piezoelectric films with inclined crystal orientations, as standard sputtering setups cannot deposit materials with pre-defined tilt angles necessary for optimal shear wave mode coupling without modifying the equipment.
Innovation Solution
A structure for a thin-film bulk acoustic resonator is created with a substrate featuring slanted cavities, allowing for the deposition of piezoelectric materials like ZnO or AlN with controlled c-axis tilt angles, enabling optimal coupling to shear wave modes without requiring modifications to the sputtering setup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standard sputtering setup is used, then manufacturing process is simple, but piezoelectric film cannot achieve inclined crystal orientation for optimal shear wave mode coupling
Solution Approach 1:
The substrate is pre-patterned with inclined trenches or grooves at the desired angle (e.g., 39 degrees) before piezoelectric film deposition. This preliminary structural preparation guides the crystal growth orientation during subsequent sputtering, enabling inclined crystal orientation without modifying the sputtering equipment itself.
Solution Approach 2:
The inclined trenches act as an intermediary structure between the standard sputtering setup and the desired inclined crystal orientation. These physical guides on the substrate surface mediate the crystal growth process, directing atoms to align at the required angle while the sputtering equipment remains unchanged.
2Manufacturing precision
If wafer is inclined relative to sputtering target, then shear wave mode coupling is optimized, but sputtering tool modification is required
Solution Approach 1:
Instead of inclining the wafer or modifying the sputtering target, the approach is inverted by creating inclined features on the substrate surface that guide crystal growth. This reverses the conventional approach of modifying deposition geometry to instead using substrate topology control.
Solution Approach 2:
The solution moves from modifying the deposition geometry (one dimension) to creating topographical features on the substrate surface (another dimension). The inclined trenches provide a surface-level solution that achieves the same crystal orientation effect without changing the sputtering setup geometry.
3Manufacturing precision
If inclined blinds or lamels are introduced, then crystal orientation is controlled, but sputtering setup complexity increases
Solution Approach 1:
The crystal orientation control function is extracted from the sputtering tool structure and transferred to the substrate itself. By removing the need for inclined blinds or lamels in the sputtering setup, the solution simplifies the deposition equipment while maintaining precise crystal orientation control through substrate-based guidance features.
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 approach allows for efficient excitation of shear wave modes with minimal longitudinal wave coupling, enhancing performance in applications like fluid-based sensors by reducing radiation losses and maintaining standard sputtering process simplicity.
Implementation Method 1
Piezoelectric resonators, that is, electric resonators based on piezoelectric materials
Implementation Method 2
typically AlN, ZnO or ScXAl1-XN) manufactured using thin film manufacturing methods
Data Source
AI summary
According to an aspect, there is provided a structure for a thin-film bulk acoustic resonator. The structure comprises a substrate (101) comprising a cavity (104) having at least one slanted flat surface (103) facing away from the cavity and a piezoelectric bulk material layer (102) deposited on said at least one slanted flat surface.