BAW Piezoelectric Layer Engineering for Frame Mode Suppression
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Solution Overview
Problem
Existing bulk acoustic wave (BAW) devices face challenges in achieving high quality factor (Q) and suppressing spurious modes while meeting performance specifications, particularly due to frame modes associated with frame structures.
Innovation Solution
The BAW devices incorporate a piezoelectric layer with an engineered region, specifically in the peripheral or frame regions, where the piezoelectric coefficient is reduced to suppress frame modes, while maintaining a high electromechanical coupling coefficient (kt2), by modifying the crystallinity and orientation of the piezoelectric layer through methods like ion implantation or varying deposition materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a frame structure is added to suppress spurious modes, then spurious mode attenuation is improved, but device complexity increases
Solution Approach 1:
The piezoelectric layer is engineered with different properties in different regions: the central acoustically active region maintains high piezoelectric coefficients for strong signal generation, while the peripheral frame region has reduced piezoelectric coefficients to suppress frame modes. This local differentiation allows the single piezoelectric layer to perform dual functions without adding separate frame structures.
2Object-generated harmful factors
If the piezoelectric layer is modified to suppress frame modes, then spurious mode attenuation is improved, but the electromechanical coupling coefficient may deteriorate
Solution Approach 1:
The piezoelectric layer is engineered with different properties in different regions: the central acoustically active region maintains high piezoelectric coefficients for strong signal generation, while the peripheral frame region has reduced piezoelectric coefficients to suppress frame modes. This local differentiation allows the single piezoelectric layer to perform dual functions without adding separate frame structures.
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 approach significantly increases the quality factor (Q) and attenuates spurious modes, improving the overall performance of BAW devices, particularly in applications like 5G New Radio filters, by effectively decoupling Q and spurious mode strengths.
Implementation Method 1
a piezoelectric layer positioned between the first electrode and the second electrode in at least the main acoustically active region
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 that includes a temperature compensation layer and a piezoelectric layer that is less piezoelectric in a peripheral region than in an acoustically active region. Related filters, multiplexers, radio frequency modules, radio frequency systems, wireless communication devices, and methods are disclosed.