Multilayer Electrode Resonator Design for High Q Factor
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Solution Overview
Problem
Conventional piezoelectric thin-film resonators face challenges in achieving high electromechanical coupling coefficients and Q factors due to difficulties in growing high-quality lead zirconate titanate or lead titanate films, orientation errors in piezoelectric film orientation, and increased electrode resistance leading to higher insertion losses.
Innovation Solution
A piezoelectric thin-film resonator design with a multilayer structure featuring a substrate, lower and upper electrodes with specific gravity differences, and a piezoelectric film, where the thickness ratio of the high specific gravity electrodes to the piezoelectric film is optimized to enhance electromechanical coupling and Q factors, while maintaining symmetric acoustic wave excitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional piezoelectric thin-film resonator structure is used, then the device can be miniaturized and implemented monolithically, but the electromechanical coupling coefficient and Q factor are insufficient due to difficulties in growing high-quality piezoelectric films and orientation errors
Solution Approach 1:
The patent changes the physical parameters of the electrode structure by introducing a multilayer configuration with different specific gravities. The lower electrode uses a first film (e.g., tungsten with high specific gravity) and a second film (e.g., molybdenum with lower specific gravity), while the upper electrode uses a third film (high specific gravity) and fourth film (lower specific gravity). This parameter change in electrode structure compensates for piezoelectric film orientation errors and improves the electromechanical coupling coefficient and Q factor without requiring perfect film growth conditions.
2Loss of energy
If electrode thickness is increased to reduce resistance, then insertion losses decrease, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent employs composite electrode structures where each electrode consists of multiple films with different specific gravities. The lower electrode comprises a first film (high specific gravity) and a second film (lower specific gravity), while the upper electrode comprises a third film (high specific gravity) and a fourth film (lower specific gravity). This composite structure reduces electrode resistance and insertion losses while maintaining manageable device complexity through systematic material selection.
3Volume of moving object
If the piezoelectric film thickness is reduced to miniaturize the resonator, then the device size decreases, but the electromechanical coupling coefficient deteriorates
Solution Approach 1:
The patent compensates for the reduced piezoelectric film thickness by optimizing the electrode structure parameters. The multilayer electrode configuration with specific gravity differences creates favorable stress distribution and electrical field concentration that enhances the electromechanical coupling coefficient even when the piezoelectric film is thin, thus enabling miniaturization without sacrificing performance.
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 improves the electromechanical coupling coefficient and Q factor, broadening the filter's pass band and reducing insertion losses, while minimizing frequency and pass-band width variations due to film thickness ratios.
Implementation Method 1
a piezoelectric film provided on the lower electrode
Implementation Method 2
Resonator, filter and electronic device
Data Source
AI summary
A resonator includes a substrate, a lower electrode, a piezoelectric film provided on the lower electrode, and an upper electrode provided on the piezoelectric film. The lower electrode includes a first film provided on the substrate, and a second film that is provided on the first film and has a specific gravity greater than that of the first film. The piezoelectric film is provided on the second film. The upper electrode includes a third film provided on the piezoelectric film, and a fourth film provided on the third film, the third film having a specific gravity greater than that of the fourth film. The third film is thicker than the second film.