Piezoelectric Acoustic Resonator Layout for Bulk Wave Isolation
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Solution Overview
Problem
Acoustic wave resonators face performance issues due to unwanted bulk mode acoustic waves, which can interfere with the operation of multiple filter devices in close proximity, leading to increased size and reduced efficiency.
Innovation Solution
Incorporating acoustic wave scattering structures, such as apodized surfaces and substrate seams, within the resonator device to scatter and inhibit bulk mode waves, allowing for the integration of multiple filter devices on a smaller footprint without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acoustic wave resonators are used in filters, then signal filtering capability is improved, but unwanted bulk mode acoustic waves are generated that interfere with adjacent filter devices
Solution Approach 1:
The patent converts the harmful bulk mode acoustic waves into beneficial surface acoustic waves by using a specially designed substrate structure with a piezoelectric layer and electrode configuration that transforms bulk wave energy into surface wave energy, thereby eliminating interference while maintaining filtering capability
Solution Approach 2:
The patent introduces an acoustic wave scattering structure as an intermediary element between the interdigitated electrodes and the substrate. This scattering structure selectively scatters bulk mode waves while allowing surface modes to propagate, thereby preventing interference with adjacent filter devices
2Productivity
If multiple filter devices are placed in close proximity, then device integration density is improved, but bulk mode acoustic waves cause interference between adjacent devices
Solution Approach 1:
The substrate structure converts harmful bulk mode waves into beneficial surface acoustic waves, allowing multiple filter devices to be integrated in close proximity without interference, thereby improving device integration density
Solution Approach 2:
The patent applies different acoustic properties to different regions of the substrate. The acoustic wave scattering structure is strategically positioned to locally scatter bulk waves in specific directions while allowing surface waves to propagate freely, enabling dense integration of multiple filter devices
3Reliability
If acoustic wave scattering structures are added to reduce bulk modes, then filter efficiency is improved, but device complexity increases
Solution Approach 1:
The patent modifies substrate parameters (piezoelectric layer thickness, electrode geometry, material properties) to inherently generate surface acoustic waves while suppressing bulk modes. This parameter optimization achieves high filter efficiency without adding complex external scattering structures
Solution Approach 2:
The interdigitated electrodes serve multiple functions: they generate surface acoustic waves for filtering and simultaneously create bulk mode waves that are converted into surface waves by the substrate structure. This multi-functionality improves filter efficiency without significantly increasing device complexity
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 implementation of acoustic wave scattering structures effectively reduces bulk mode acoustic waves, enabling the creation of compact, high-performance acoustic resonator devices with improved filter efficiency and reduced spurious modes.
Implementation Method 1
an acoustic wave scattering structure within the substrate that is distanced away from but sufficiently close to the interdigitated metal so as to scatter the non-lateral component of the acoustic waves
Implementation Method 2
an interdigitated metal disposed over the piezoelectric layer, wherein the interdigitated metal is configured to generate acoustic waves within an acoustically active region
Data Source
AI summary
The present disclosure provides an acoustic resonator device, among other things. One example of the disclosed acoustic resonator device includes a substrate having a carrier layer, a first layer disposed over the carrier layer, and a piezoelectric layer disposed over the first layer. The acoustic resonator device is also disclosed to include an interdigitated metal disposed over the piezoelectric layer, where the interdigitated metal is configured to generate acoustic waves within an acoustically active region. The acoustic resonator device is further disclosed to include an acoustic wave scattering structure.