SAW Piezoelectric Layer Thickness for Spurious Wave Suppression
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Solution Overview
Problem
Surface acoustic wave devices face significant challenges in suppressing spurious wave excitation, particularly when the thickness of the piezoelectric layer is not optimally matched with the substrate, leading to increased spurious amplitude and frequency intervals.
Innovation Solution
A surface acoustic wave device configuration is implemented, where the thickness of the piezoelectric layer is set to 2.4λ or less, utilizing a sapphire substrate with specific Euler angles and cutting angles to minimize spurious wave excitation, thereby reducing the amplitude and frequency intervals of spurious waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piezoelectric layer thickness is increased to improve SAW energy confinement, then the SAW energy confinement is improved, but spurious wave excitation increases
Solution Approach 1:
The invention changes the thickness parameter of the piezoelectric layer to a specific range (0.15λ to 0.30λ for C-plane sapphire, 0.30λ to 0.35λ for A-plane and R-plane sapphire) to simultaneously achieve SAW energy confinement and suppress spurious wave excitation. This optimal parameter selection resolves the contradiction by finding the threshold value where both requirements are satisfied.
2Object-generated harmful factors
If the piezoelectric layer thickness is decreased to reduce spurious wave excitation, then spurious wave amplitude is reduced, but SAW energy confinement deteriorates
Solution Approach 1:
The invention establishes a minimum thickness threshold (0.15λ for C-plane, 0.30λ for A-plane and R-plane) below which SAW energy confinement deteriorates. By setting the thickness parameter within the optimal range rather than minimizing it, the invention prevents spurious wave excitation while maintaining adequate energy confinement.
3Object-generated harmful factors
If the piezoelectric layer thickness is optimized to suppress spurious waves, then spurious wave intensity is suppressed, but manufacturing precision requirements increase
Solution Approach 1:
The invention provides specific thickness ranges (0.15λ-0.30λ for C-plane, 0.30λ-0.35λ for A-plane and R-plane) that offer a buffer zone for manufacturing tolerances. This range-based specification rather than a single value allows for practical manufacturing precision while still achieving spurious wave suppression.
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 suppresses the intensity and number of spurious waves, enhancing the performance of surface acoustic wave devices by maintaining low loss and conductance values near the anti-resonance frequency, while confining SAW energy within the piezoelectric layer.
Implementation Method 1
a surface acoustic wave device that combines a piezoelectric layer and a substrate to suppress excitation of spurious waves
Data Source
AI summary
A surface acoustic wave device with suppressed excitation of spurious waves. The surface acoustic wave device comprises: a support substrate; a piezoelectric layer formed on the support substrate; and an IDT electrode on the piezoelectric layer, wherein when a wavelength of a surface acoustic wave excited at the IDT electrode is λ, thickness of the piezoelectric layer is 2.4λ or less.