Acoustic Wave Stack Using Aluminum Oxide to Suppress Higher-Order Modes
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Solution Overview
Problem
Existing acoustic wave devices are not effective in reducing higher order modes across a wide band of frequencies, particularly those higher than or equal to 1.5 times the resonance frequency.
Innovation Solution
An acoustic wave device comprising a crystal substrate, an aluminum oxide layer, a piezoelectric layer made of lithium tantalate or lithium niobate, and an interdigital transducer electrode, where the lithium tantalate layer is indirectly or directly disposed on the aluminum oxide layer with a low velocity film in between, optimizing the Euler angles and thickness of the aluminum oxide layer to reduce higher order modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional acoustic wave device structure is used, then the device can operate at resonance frequency, but it cannot effectively reduce higher order modes in a wide band of frequencies
Solution Approach 1:
An aluminum oxide layer is introduced as an intermediary between the crystal substrate and the piezoelectric layer. This intermediate layer specifically suppresses higher order modes while allowing the device to maintain operation across a wide frequency band, resolving the contradiction between mode reduction and frequency coverage
Solution Approach 2:
The device employs a composite structure combining crystal substrate, aluminum oxide layer, and piezoelectric layer (lithium tantalate or lithium niobate). This composite material approach enables simultaneous achievement of higher order mode reduction and wide band frequency operation that cannot be realized with single materials
2Reliability
If the aluminum oxide layer thickness is increased to reduce higher order modes, then mode suppression improves, but the device complexity and manufacturing precision requirements increase
Solution Approach 1:
The patent specifies optimal thickness ranges for the aluminum oxide layer (0.05λ to 1.5λ, preferably 0.1λ to 0.5λ) to achieve effective higher order mode suppression. By defining specific parameter ranges rather than requiring precise single-value control, the invention balances mode suppression performance with manufacturability
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
The proposed acoustic wave device successfully reduces or prevents higher order modes in a wide band of frequencies, improving the stability and efficiency of acoustic wave propagation by effectively managing the impedance ratio and phase characteristics.
Implementation Method 1
a piezoelectric layer on the aluminum oxide layer
Implementation Method 2
an interdigital transducer electrode on the piezoelectric layer and including multiple electrode fingers
Data Source
AI summary
An acoustic wave device includes a crystal substrate, an aluminum oxide layer on the crystal substrate, a lithium tantalate layer on the aluminum oxide layer, and an interdigital transducer electrode on the lithium tantalate layer and including multiple first and second electrode fingers.