Acoustic Wave Membrane Layout for Piezoelectric Thickness Uniformity
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Solution Overview
Problem
Existing acoustic wave devices face issues with variations in the thickness of the piezoelectric layer, which can deteriorate electrical characteristics.
Innovation Solution
The acoustic wave device incorporates a support with a cavity portion and a membrane portion of the piezoelectric layer designed with a hammerhead shape, where the outer peripheral edges of the membrane portions in the first and second directions are located on the outer side relative to the central portion, reducing or preventing thickness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a through-hole is provided in the support substrate, then the acoustic wave device can be constructed, but variations in the thickness of the piezoelectric layer occur
Solution Approach 1:
The support substrate is divided into a solid portion and a cavity portion, creating a segmented structure that provides mechanical support while reducing thickness variations in the piezoelectric layer. The solid portion maintains structural integrity and thickness uniformity, while the cavity portion is strategically positioned to avoid critical areas.
Solution Approach 2:
The piezoelectric layer is designed with different structural characteristics in different regions. The membrane portion overlapping the cavity has a specific shape (extending in first and second directions with outer peripheral edges positioned outward) to compensate for thickness variations, while other portions maintain standard characteristics.
2Reliability
If the piezoelectric layer is made thin to improve electrical characteristics, then device performance improves, but thickness variations become more significant
Solution Approach 1:
The membrane portion of the piezoelectric layer is pre-shaped with extended outer peripheral edges in the first and second directions before operation. This preliminary structural configuration compensates for thickness variations that would otherwise occur during device operation, ensuring consistent electrical characteristics.
Solution Approach 2:
The membrane portion is designed with an asymmetric shape where the outer peripheral edges in the first and second directions extend beyond the central portion. This asymmetric configuration strategically positions thicker regions to compensate for thickness variations, maintaining overall thickness consistency.
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 ensures uniform thickness of the piezoelectric layer, thereby improving the electrical characteristics and performance of the acoustic wave device.
Implementation Method 1
a piezoelectric layer (14) on the support (13)
Implementation Method 2
a membrane portion (15) of the piezoelectric layer (14)
Data Source
AI summary
An acoustic wave device includes a support including a support substrate, a piezoelectric layer on the support, and an excitation electrode on the piezoelectric layer. A cavity portion is provided in the support and overlaps at least a portion of the excitation electrode. A portion of the piezoelectric layer that overlaps the cavity portion is a membrane portion. The membrane portion includes first and second directions orthogonal or substantially orthogonal to each other. The membrane portion includes a central portion in the center in the first direction, first and second portions facing each other across the central portion in the first direction, and an outer peripheral edge. At least a portion of the outer peripheral edge of the first and second portions of the membrane portion is located in an outer side portion in the second direction relative to the outer peripheral edge in the central portion.