Acoustic Wave Wafer Void Layout for Spurious Emission Suppression
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Solution Overview
Problem
Existing acoustic wave devices face challenges in reducing spurious emissions while maintaining the main response, as the methods of roughening the support substrate and providing voids between the substrate and piezoelectric layer are not sufficient in effectively suppressing spurious emissions.
Innovation Solution
An acoustic wave device is designed with a support substrate, a piezoelectric layer, and an insulating layer having void regions with different extending directions, where the width in the extending direction is longer than in the orthogonal direction, to attenuate bulk waves and reduce spurious emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the upper surface of the support substrate is roughened, then spurious emissions are reduced, but the main response deteriorates
Solution Approach 1:
The insulating layer is designed with non-uniform void structures where the void ratio varies in different regions. Specifically, the void ratio increases from the center toward the edges of the insulating layer, creating local quality variations that differently affect bulk waves versus surface acoustic waves, thereby reducing spurious emissions while preserving main response
Solution Approach 2:
The void structures in the insulating layer are designed with asymmetric characteristics, including voids with different extending directions and asymmetric void ratios relative to the center of the insulating layer. This asymmetric configuration creates different acoustic impedance conditions for waves traveling in different directions, effectively suppressing spurious bulk waves while maintaining the main surface acoustic wave response
2Object-generated harmful factors
If a layer having voids is provided between the support substrate and the piezoelectric layer, then spurious emissions are reduced, but the main response deteriorates
Solution Approach 1:
The void ratio in the insulating layer is specifically optimized as a controllable parameter, with the void ratio increasing from the center toward the edges. This parameter gradient allows selective attenuation of bulk waves (which pass through the entire layer) while maintaining transmission of surface acoustic waves (which propagate along the interface), thereby reducing spurious emissions without deteriorating the main response
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 solution effectively reduces spurious emissions by attenuating bulk waves through the unique void structure, while maintaining the main response, as demonstrated by experimental results showing lower spurious responses in samples with the described configuration compared to comparative examples.
Implementation Method 1
an insulating layer provided between the support substrate and the piezoelectric layer, the insulating layer having, in at least a part thereof, a plurality of void regions of which extending directions are different from each other... to attenuate bulk waves and reduce spurious emissions
Data Source
AI summary
An acoustic wave device includes a support substrate, a piezoelectric layer provided on the support substrate, at least a pair of comb-shaped electrodes provided on the piezoelectric layer, each of the comb-shaped electrodes including a plurality of electrode fingers, and an insulating layer provided between the support substrate and the piezoelectric layer, the insulating layer having, in at least a part thereof, a plurality of void regions of which extending directions are different from each other when viewed from a thickness direction of the support substrate, a width in the corresponding extending direction of each of the void regions being longer than a width in a direction orthogonal to the corresponding extending direction when viewed from the thickness direction of the support substrate.