Engineered Piezoelectric Layer for BAW 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, where the piezoelectric coefficient is reduced in peripheral regions to suppress frame modes, while maintaining a higher coefficient in the main acoustically active region, using techniques such as ion implantation or varying deposition materials to alter crystallinity and orientation.
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 coefficient for strong signal generation, while the peripheral frame region has reduced piezoelectric coefficient to suppress frame modes. This local differentiation allows simultaneous achievement of high Q factor and spurious mode attenuation without adding overall device complexity
Solution Approach 2:
The piezoelectric coefficient parameter is selectively modified in the peripheral region through ion implantation or alternative deposition techniques. By changing this material parameter locally, the frame structure's piezoelectric response is suppressed, thereby attenuating frame modes and spurious signals without requiring additional structural elements
2Manufacturing precision
If ion implantation is used to engineer the piezoelectric layer, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The piezoelectric layer is deposited with uniform properties first, then ion implantation is performed as a subsequent step to selectively modify the peripheral region. This preliminary deposition followed by targeted modification allows precise control over the piezoelectric coefficient distribution while using established manufacturing techniques
Solution Approach 2:
The manufacturing process is segmented into distinct steps: initial piezoelectric layer deposition, masking of the central region, and ion implantation of the peripheral region. This segmentation allows each step to be optimized independently, maintaining manufacturing precision while managing process 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
This approach significantly increases the quality factor (Q) and attenuates spurious modes, while maintaining electromechanical coupling coefficient (kt2), effectively decoupling Q and spurious mode strength, and enhancing performance in applications like 5G New Radio filters.
Implementation Method 1
In BAW resonators, acoustic waves propagate in the bulk of a piezoelectric layer
Implementation Method 2
using techniques such as ion implantation or varying deposition materials to alter crystallinity and orientation
Data Source
AI summary
Aspects of this disclosure relate to a method of manufacturing a bulk acoustic wave device that includes forming a piezoelectric layer over an electrode such that the piezoelectric layer has a greater magnitude effective piezoelectric coefficient in a main acoustically active region of the bulk acoustic wave device than in a peripheral region of the bulk acoustic wave device. Related bulk acoustic wave devices, filters, multiplexers, radio frequency modules, radio frequency systems, wireless communication devices, and methods are disclosed.