Multilayer BAW Resonator Structure for Coupling Coefficient Tuning
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Solution Overview
Problem
Current BAW resonators face challenges in achieving optimal electromechanical coupling coefficients, which limits the precision in designing high-frequency filters with flat passbands and steep filter skirts, as the choice of piezoelectric material restricts the ability to optimize filter performance.
Innovation Solution
A multilayer piezoelectric structure with two or more piezoelectric layers having different electromechanical coupling coefficients, allowing for precise control of the effective coupling coefficient by varying the thickness ratios and doping levels, enabling more optimized BAW resonators and filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single piezoelectric material is used in BAW resonators, then the device structure is simple, but the electromechanical coupling coefficient cannot be precisely optimized for high-frequency filter performance
Solution Approach 1:
The piezoelectric structure is divided into multiple layers with different materials or doping concentrations, each layer contributing differently to the overall electromechanical coupling coefficient. This segmentation allows independent optimization of each layer's properties to achieve the desired effective coupling coefficient while maintaining manufacturing feasibility
Solution Approach 2:
Different regions of the piezoelectric structure are assigned different material compositions or doping levels to create local variations in electromechanical coupling properties. This enables precise control of the effective coupling coefficient by optimizing the local properties of each layer according to its specific function in the resonator
2Adaptability or versatility
If the piezoelectric structure is simplified to a single layer, then the manufacturing process is easier, but the ability to tune electromechanical coupling coefficient is limited
Solution Approach 1:
The invention varies parameters such as doping concentration, layer thickness, and material composition across multiple piezoelectric layers to achieve different electromechanical coupling coefficients. By changing these parameters in a controlled manner, the effective coupling coefficient can be precisely tuned to match filter design requirements while using standard manufacturing processes
3Reliability
If multiple piezoelectric layers with different coupling coefficients are used, then the filter performance can be optimized, but the device structure becomes more complex
Solution Approach 1:
The piezoelectric structure employs composite construction with multiple layers of different materials or compositions (e.g., AlN with different Sc doping levels). This composite approach combines the advantages of each material to achieve superior overall performance with enhanced electromechanical coupling coefficient tunability while maintaining structural integrity
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 allows for the precise tuning of electromechanical coupling coefficients, enhancing the performance of BAW resonators and filters by widening passbands and improving frequency response characteristics.
Implementation Method 1
a multilayer piezoelectric structure between the bottom electrode and the top electrode. The multilayer piezoelectric structure has a first piezoelectric layer having a first electromechanical coupling coefficient and a second piezoelectric layer having a second electromechanical coupling coefficient
Data Source
AI summary
A bulk acoustic wave (BAW) resonator has a bottom electrode, a top electrode over the bottom electrode, and a multilayer piezoelectric structure between the bottom electrode and the top electrode. The multilayer piezoelectric structure has a first piezoelectric layer having a first electromechanical coupling coefficient and a second piezoelectric layer having a second electromechanical coupling coefficient that is different than the first electromechanical coupling coefficient.