Acoustic Wave Structure With Dual Euler-Angle Piezoelectric Layers
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Solution Overview
Problem
Existing acoustic wave devices suffer from spurious responses of Rayleigh modes on the lower frequency side and higher-order modes on the higher frequency side, deteriorating device characteristics.
Innovation Solution
The acoustic wave device incorporates a support substrate with a first and second piezoelectric layer made of lithium tantalate or lithium niobate, where the Euler angles of the second piezoelectric layer differ from those of the first, and includes a low and high acoustic velocity film to confine acoustic energy, reducing spurious responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single piezoelectric layer with IDT electrode is used, then the device structure is simple, but spurious responses of Rayleigh mode and higher-order mode occur deteriorating device characteristics
Solution Approach 1:
The single piezoelectric layer is segmented into two separate piezoelectric layers (first and second piezoelectric layers) with different Euler angles. This segmentation allows each layer to contribute differently to acoustic wave propagation, suppressing spurious responses while maintaining overall device functionality.
Solution Approach 2:
The device uses a composite structure combining two piezoelectric layers with different crystal orientations (different Euler angles). This composite configuration leverages the complementary properties of each layer to achieve both structural feasibility and suppression of unwanted acoustic modes.
2Reliability
If two piezoelectric layers with different Euler angles are used, then spurious responses are reduced or prevented, but the device structure becomes more complex
Solution Approach 1:
Different regions (layers) of the piezoelectric structure are assigned different Euler angles tailored to their specific functional requirements. The first piezoelectric layer has one Euler angle optimized for its position, while the second layer has a different Euler angle optimized for its position, allowing local optimization without requiring complete redesign of the entire structure.
3Reliability
If spurious responses are suppressed by adding piezoelectric layers, then device characteristics improve, but manufacturing complexity increases
Solution Approach 1:
The invention changes the Euler angle parameter between the two piezoelectric layers to achieve suppression of spurious responses. This parameter change approach allows for suppression of unwanted modes while using standard piezoelectric material deposition processes, avoiding the need for entirely new manufacturing techniques.
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 reduces or prevents spurious responses, enhancing the Q factor and temperature coefficient of frequency while adjusting acoustic velocity, thereby improving device performance.
Implementation Method 1
a first piezoelectric layer 3A and a second piezoelectric layer 3B which are on the support substrate 2
Implementation Method 2
a low and high acoustic velocity film to confine acoustic energy
Data Source
AI summary
An acoustic wave device includes a support substrate, first and second piezoelectric layers, and an IDT electrode. The first and second piezoelectric layers are on the support substrate. The IDT electrode is on the first piezoelectric layer and includes electrode fingers. The second piezoelectric layer is between the first piezoelectric layer and the support substrate. The first and second piezoelectric layers are made of lithium tantalate or lithium niobate. Euler angles of the second piezoelectric layer are different from Euler angles of the first piezoelectric layer.