BAW Resonator Electrodes for Temperature-Stable Frequency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional bulk acoustic wave (BAW) resonators exhibit significant temperature dependence in their resonant frequencies, which affects their performance and reliability across varying temperature ranges.
Innovation Solution
The use of a BAW resonator design that incorporates a piezoelectric layer doped with rare earth elements and electrodes made from niobium alloys, which reduces the temperature coefficient of the resonant frequency by optimizing the thickness and composition of the electrodes and piezoelectric layer, thereby enhancing the electromechanical coupling coefficient and quality factors of the resonances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional BAW resonator design is used, then manufacturing is simpler, but temperature dependence of resonant frequency is significant
Solution Approach 1:
The patent applies parameter changes by carefully controlling and optimizing specific parameters including the thickness of the piezoelectric layer, the thickness and composition of electrode layers, and the doping concentration of rare earth elements in the piezoelectric material. These parameter optimizations enable temperature compensation that reduces the temperature coefficient of resonant frequency while maintaining a relatively simple device structure
Solution Approach 2:
The patent employs composite materials by using a piezoelectric layer doped with rare earth elements (such as scandium, yttrium, or lanthanum) combined with specific electrode materials. This composite structure creates synergistic effects where the doped piezoelectric material and electrode materials work together to achieve temperature compensation, reducing temperature dependence without significantly increasing device complexity
2Reliability
If piezoelectric layer thickness is increased to improve kt2, then bandwidth is improved, but resonant frequency decreases
Solution Approach 1:
The patent uses parameter changes by optimizing the thickness of the piezoelectric layer to a specific range that balances bandwidth and resonant frequency requirements. Additionally, the patent changes the composition parameter by introducing rare earth element doping, which enhances the electromechanical coupling coefficient kt2, allowing for improved bandwidth while maintaining higher resonant frequencies than conventional designs
3Reliability
If electrode thickness is increased to improve Q-factor, then quality factor is improved, but series resistance increases
Solution Approach 1:
The patent applies composite materials by using specific electrode material compositions and structures that optimize the balance between Q-factor and series resistance. The multi-layer electrode structure with specific thickness ratios allows for improved quality factor while controlling series resistance through material selection and geometric optimization
4Reliability
If rare earth doping is added to piezoelectric material, then electromechanical coupling is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the doping concentration of rare earth elements to specific ranges that achieve improved electromechanical coupling while maintaining compatibility with existing manufacturing processes. The controlled doping levels ensure that the material can be deposited using standard thin-film techniques without requiring entirely new manufacturing approaches
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 design allows for BAW resonators with reduced temperature dependence, enabling improved performance and reliability across a wide temperature range by adjusting the thickness of the piezoelectric layer and electrodes, resulting in lower series resistance and higher quality factors for both series and parallel resonances.
Implementation Method 1
a piezoelectric layer between the first electrode and the second electrode. The piezoelectric layer is of a piezoelectric material doped with at least one rare earth element
Implementation Method 2
At least one of the first electrode material and the second electrode material is a niobium alloy that, relative to molybdenum as the respective at least one of the first electrode material and the second electrode material, reduces the temperature coefficient of the resonant frequency of the BAW resonator
Data Source
AI summary
A bulk acoustic wave (BAW) resonator having a first electrode, a second electrode, and a piezoelectric layer between the first electrode and the second electrode. The first electrode is of a first electrode material. The second electrode is of a second electrode material. The piezoelectric layer is of a piezoelectric material doped with at least one rare earth element. The BAW resonator has a resonant frequency dependent at least in part on respective thicknesses and materials of the first electrode, the second electrode and the piezoelectric layer. The resonant frequency has a temperature coefficient. At least one of the first electrode and the second electrode includes a niobium alloy electrode material that, relative to molybdenum as the electrode material, reduces the temperature coefficient of the resonant frequency of the BAW resonator.