Acoustic Wave Electrode Layout to Reduce Leaky Waves and Ripples
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Solution Overview
Problem
Existing acoustic wave devices exhibit significant ripples in frequency characteristics due to leaky waves and require reflectors for resonance, which hinder miniaturization and increase propagation loss.
Innovation Solution
The acoustic wave device incorporates a piezoelectric layer with a support substrate and functional electrodes, featuring interdigitated electrodes and insulating films or voids to minimize overlap regions, allowing bulk waves to propagate without reflectors, thereby reducing ripples and enhancing resonance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reflectors are used to achieve resonance, then resonance characteristics are improved, but device size increases and propagation loss increases
Solution Approach 1:
The patent extracts and eliminates the reflector component from the acoustic wave device. By using a piezoelectric substrate with specific crystal orientation (YX-lithium niobate or YX-lithium tantalate) and configuring interdigitated electrodes directly on the substrate, the invention achieves resonance without requiring external reflectors, thereby reducing device size and propagation loss while maintaining resonance characteristics
Solution Approach 2:
The patent introduces a piezoelectric layer with specific material properties (YX-cut lithium niobate or lithium tantalate) as an intermediary between the electrodes and the substrate. This intermediate piezoelectric layer enables effective acoustic wave generation and resonance without the need for reflectors, resolving the contradiction between achieving good resonance characteristics and minimizing device size
2Object-generated harmful factors
If overlap regions between electrodes and piezoelectric layer are reduced, then leaky wave propagation is minimized, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating distinct regions in the electrode structure: overlap regions where electrodes contact the piezoelectric layer to generate acoustic waves, and non-overlap regions where insulating films are formed to prevent leaky wave propagation. This localized differentiation of electrode regions allows the device to minimize harmful leaky waves while maintaining ease of manufacture through standard semiconductor fabrication processes
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 achieves improved resonance characteristics with reduced ripples and increased fractional band width, enabling miniaturization without decreasing the Q-factor, and minimizing leaky wave propagation.
Implementation Method 1
a piezoelectric layer with a support substrate and functional electrodes... allowing bulk waves to propagate
Implementation Method 2
enhancing resonance characteristics... achieves improved resonance characteristics with reduced ripples and increased fractional band width
Data Source
AI summary
An acoustic wave device includes a support substrate, a piezoelectric layer, and a functional electrode. As seen in a first direction of the support substrate, the piezoelectric layer overlaps the support substrate. The functional electrode extends over a first major surface of the piezoelectric layer. A space is opposite to the first major surface of the piezoelectric layer and at or adjacent to a second major surface of the piezoelectric layer. In the first direction, the functional electrode extends over an overlap region that overlaps the space, and a non-overlap region that does not overlap the space. In the non-overlap region, at least one of an insulating film and a void is located between the functional electrode and the piezoelectric layer.