Acoustic Wave Filter Substrate Structure for Lower Spurious Emissions
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Solution Overview
Problem
Existing acoustic wave devices face issues with spurious emissions due to irregularly uneven support substrate surfaces, leading to variations in device characteristics and inconsistent performance.
Innovation Solution
A piezoelectric substrate with comb-shaped electrodes and a support substrate featuring regularly arranged protruding and recessed portions, bonded with an insulating layer, which scatters or absorbs bulk waves to reduce spurious emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the support substrate surface is roughened to reduce spurious emissions, then spurious emissions are reduced, but the surface becomes irregularly uneven causing variations in device characteristics
Solution Approach 1:
The support substrate surface is segmented into multiple protruding portions and recessed portions that are regularly arranged in a periodic pattern. This segmentation transforms the continuous rough surface into discrete, regularly spaced structures that scatter bulk waves effectively while maintaining manufacturing precision and device characteristic uniformity.
Solution Approach 2:
The support substrate is designed with specific local structures (protruding and recessed portions) that have controlled dimensions and arrangements. These local quality modifications create regions optimized for scattering bulk waves while maintaining overall surface regularity, thereby reducing spurious emissions without causing device characteristic variations.
2Manufacturing precision
If a flat support substrate surface is used, then manufacturing is easier and device characteristics are more consistent, but spurious emissions increase
Solution Approach 1:
Instead of using a completely flat surface, the support substrate incorporates segmented protruding and recessed portions arranged in a regular periodic pattern. This segmentation provides the necessary surface irregularity for scattering bulk waves while maintaining enough regularity for consistent manufacturing and uniform device characteristics.
Solution Approach 2:
The invention converts what would normally be considered a defect (surface irregularity) into a beneficial feature. The regularly arranged protruding and recessed portions, which might seem to reduce manufacturing precision, actually serve to scatter bulk waves and reduce spurious emissions, transforming a potential harm into a benefit.
3Object-generated harmful factors
If the entire support substrate surface is roughened, then spurious emissions are reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The support substrate surface is segmented into discrete protruding and recessed portions with specific dimensions and periodic arrangements, rather than applying uniform roughening across the entire surface. This segmented approach reduces manufacturing complexity by providing clear geometric definitions that are easier to control and manufacture compared to continuous roughening.
Solution Approach 2:
The invention changes the surface topology parameters by introducing specific protruding and recessed portions with controlled dimensions, spacing, and patterns. This parameter-based approach allows for precise control of scattering properties while simplifying the manufacturing process compared to traditional roughening methods that require complex process control.
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 solution achieves uniform characteristics and reduced spurious emissions by scattering or absorbing bulk waves, improving the performance and consistency of acoustic wave devices.
Implementation Method 1
a boundary face between the insulating layer and the support substrate being provided along the protruding portions and/or the recessed portions
Implementation Method 2
a piezoelectric substrate; a pair of comb-shaped electrodes located on the piezoelectric substrate
Data Source
AI summary
An acoustic wave device includes: a piezoelectric substrate: a pair of comb-shaped electrodes located on the piezoelectric substrate, each of the comb-shaped electrodes including a plurality of electrode fingers; a support substrate having protruding portions and/or recessed portions in a region overlapping with the pair of comb-shaped electrodes in plan view, the protruding portions and/or recessed portions being regularly arranged; and an insulating layer directly or indirectly bonded between the piezoelectric substrate and the support substrate, a boundary face between the insulating layer and the support substrate being provided along the protruding portions and/or the recessed portions.