BAW Resonator Dielectric Frame Structure for Spurious Mode Suppression
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Solution Overview
Problem
Existing bulk acoustic wave (BAW) devices face challenges in achieving high quality factor (Q) while effectively suppressing spurious modes, which can lead to energy losses and performance degradation.
Innovation Solution
Incorporating a dielectric layer with different material properties than the piezoelectric layer, positioned laterally between portions of the piezoelectric layer, to suppress frame modes and increase Q, while maintaining electromechanical coupling coefficient (kt2).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezoelectric layer is used in BAW devices to enable acoustic wave propagation, then electromechanical coupling is achieved, but spurious frame modes are generated causing energy losses and reduced quality factor
Solution Approach 1:
A dielectric layer is introduced as an intermediary element between the piezoelectric layer and the frame structure. This dielectric layer has different acoustic impedance and piezoelectric properties compared to the piezoelectric layer, thereby suppressing the generation and propagation of spurious frame modes while allowing the main acoustic wave mode to propagate effectively through the piezoelectric layer
Solution Approach 2:
The dielectric layer is selectively positioned in specific regions where frame modes are generated, particularly at the boundaries and edges of the piezoelectric layer. This localized application of different material properties targets the harmful frame modes without affecting the overall electromechanical coupling of the device
2Object-generated harmful factors
If frame structures are added to suppress spurious modes, then mode suppression is improved, but device complexity increases
Solution Approach 1:
The dielectric layer is merged with existing structural elements of the BAW device, such as being integrated into the frame structure or positioned between existing layers. This combination approach achieves spurious mode suppression without adding separate, independent components, thereby minimizing the increase in 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 dielectric layer effectively suppresses frame modes, significantly increasing the quality factor (Q) and attenuating spurious modes, thereby enhancing BAW device performance.
Implementation Method 1
The dielectric layer includes a material that has an acoustic impedance with a magnitude that is greater than a magnitude of an acoustic impedance of the piezoelectric layer
Implementation Method 2
In BAW resonators, acoustic waves propagate in the bulk of a piezoelectric layer
Data Source
AI summary
Aspects of this disclosure relate to a bulk acoustic wave device having a main acoustically active region and a frame region. The bulk acoustic wave device can include a first electrode, a second electrode spaced apart from the first electrode in a first direction, a frame structure in the frame region, a piezoelectric layer positioned between the first electrode and the second electrode in at least the main acoustically active region, and a dielectric layer in at least part of the frame region such that the piezoelectric layer is positioned between portions of the dielectric layer in a second direction different from the first direction. The dielectric layer can include a different material than the piezoelectric layer.