Bulk Acoustic Resonator Structure for kt2 Control and High Q
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Solution Overview
Problem
The existing methods for controlling the kt2 value in bulk acoustic resonators, such as doping piezoelectric bodies with materials, lead to increased costs and decreased Q value, limiting performance improvement.
Innovation Solution
A bulk acoustic resonator design with a substrate and a resonant portion featuring stacked electrodes and piezoelectric layers, including an insertion layer with varying piezoelectric coefficients and controlled thickness ratios, and a bent portion with a dielectric insertion layer, to enhance kt2 implementation and reduce interfacial loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If doping method is used to control kt2 value, then kt2 value can be adjusted, but manufacturing cost increases and Q value decreases
Solution Approach 1:
The piezoelectric layer is divided into multiple layers with different piezoelectric coefficients. By segmenting the single piezoelectric layer into first and second piezoelectric layers with different coefficients (d33, d31, d32, or d15), the design enables kt2 value control without requiring doping, thereby maintaining high Q values while achieving the desired kt2 characteristics
Solution Approach 2:
Different regions of the piezoelectric structure are assigned different piezoelectric coefficients. The first piezoelectric layer has different piezoelectric coefficients than the second piezoelectric layer, creating local quality variations that enable precise kt2 value control. This local differentiation allows optimization of specific regions for different functional requirements without affecting the entire structure
2Adaptability or versatility
If doping method is used to control kt2 value, then kt2 value can be adjusted, but manufacturing cost increases
Solution Approach 1:
Instead of using complex doping processes to adjust kt2 values, the invention segments the piezoelectric layer into multiple undoped layers with inherently different piezoelectric coefficients. This approach simplifies manufacturing by eliminating doping steps while still achieving kt2 value control through the layered structure
Solution Approach 2:
The invention uses a composite structure of multiple piezoelectric layers with different coefficients rather than a single doped material. This composite approach allows kt2 value control through structural composition rather than chemical doping, reducing manufacturing complexity and cost
3Reliability
If multiple piezoelectric layers with different coefficients are used, then kt2 value can be controlled without doping, but device structure becomes more complex
Solution Approach 1:
The piezoelectric layer is segmented into multiple layers with different piezoelectric coefficients, where the first piezoelectric layer has different coefficients than the second piezoelectric layer. This segmentation enables kt2 value control and maintains high Q values while using standard undoped materials and conventional manufacturing processes
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 design achieves improved Q performance, flexibility in kt2 area design, and cost-effective manufacturing by minimizing interfacial loss and maintaining high efficiency.
Implementation Method 1
a bulk acoustic resonator (BAW) may be a thin film device configured as a filter, which may generate resonance using piezoelectric properties by depositing a piezoelectric dielectric material on a silicon wafer
Data Source
AI summary
An acoustic resonator includes a substrate and a resonant portion. The resonant portion has a central portion in which a first electrode, a first piezoelectric layer, a second piezoelectric layer, and a second electrode are stacked in order on the substrate, and an extension portion extending outwardly from the central portion and including an insertion layer. A ratio of an average thickness of the first piezoelectric layer to an average thickness of the second piezoelectric layer is 18.4% to 40%.