BAW Resonator Electrode with Embedded SiO2 for Frequency Stability
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Solution Overview
Problem
Film bulk acoustic wave resonators suffer from spurious acoustic waves due to transverse acoustic waves generated perpendicular to the main acoustic wave, degrading frequency response, and temperature variations affect operating frequency, necessitating improved temperature compensation.
Innovation Solution
Incorporating silicon dioxide or similar materials with a positive temperature coefficient within the electrodes of the resonator to mitigate spurious waves and temperature-induced frequency changes, with the material being patterned or unpatterned and positioned closer to the piezoelectric layer to enhance effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If temperature compensating material is added to the electrode, then frequency stability over temperature is improved, but device complexity increases
Solution Approach 1:
The temperature compensating material (silicon dioxide) is merged with the electrode structure by embedding it within the bottom electrode layer. This integration allows the electrode to simultaneously perform its electrical function and provide temperature compensation, reducing device complexity while maintaining frequency stability.
Solution Approach 2:
The bottom electrode is formed as a composite structure combining copper (for electrical conductivity) and silicon dioxide (for temperature compensation). This composite material approach enables dual functionality within a single layered structure, improving frequency stability without significantly increasing device complexity.
2Object-generated harmful factors
If silicon dioxide layer is embedded in the electrode, then spurious acoustic waves are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The silicon dioxide layer is positioned locally within the bottom electrode at the interface with the piezoelectric layer, where it most effectively suppresses spurious acoustic waves. The layer is not distributed throughout the entire device but concentrated at the critical location, reducing manufacturing precision requirements while maintaining effectiveness.
Solution Approach 2:
The silicon dioxide layer acts as an intermediary between the copper electrode and the piezoelectric layer, mediating the mechanical stress and acoustic wave interactions. This intermediary position allows it to effectively suppress spurious waves generated at the piezoelectric-electrode interface without requiring precise positioning throughout the entire structure.
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
Reduces spurious acoustic waves and minimizes frequency variation with temperature, improving quality factor, electromechanical coupling coefficient, and reducing resonator size while maintaining or enhancing resonance frequency stability.
Implementation Method 1
the temperature compensating material has a positive temperature coefficient of frequency
Implementation Method 2
a layer of piezoelectric material disposed between a top electrode and a bottom electrode
Data Source
AI summary
Aspects and embodiments disclosed herein include a film bulk acoustic wave resonator comprising a layer of piezoelectric material disposed between a top electrode and a bottom electrode and a temperature compensating material disposed within one of the top electrode or bottom electrode.