Piezoelectric Thin-Film Resonator Electrode Thickness Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional piezoelectric thin-film resonators face challenges in achieving high electromechanical coupling coefficients without degrading other characteristics, such as increased electrode resistance and unstable resonant characteristics, particularly when using materials like PZT or AlN, and require complex control processes for film orientation and thickness ratios.
Innovation Solution
A piezoelectric thin-film resonator design where the upper electrode has a greater film thickness than the lower electrode, with specific thickness ratios and materials like ruthenium, to enhance the electromechanical coupling coefficient without increasing insertion loss or degrading other characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piezoelectric film is made of PZT or PbTiO3 to increase the electromechanical coupling coefficient, then the electromechanical coupling coefficient is improved, but it becomes difficult to form a high-quality thin film and practical resonant characteristics cannot be obtained
Solution Approach 1:
The patent changes the material parameter from PZT/PbTiO3 to AlN, and adjusts the film thickness parameter to achieve high electromechanical coupling coefficient while maintaining manufacturability and resonant characteristics
Solution Approach 2:
The patent uses AlN which is easier to manufacture as a thin film compared to PZT or PbTiO3, sacrificing the need for complex material processing while achieving the desired performance through optimized film thickness
2Reliability
If the film thickness ratio of the piezoelectric film to the electrodes is adjusted to increase the electromechanical coupling coefficient, then the electromechanical coupling coefficient is improved, but the electrode resistance increases and insertion loss degrades
Solution Approach 1:
The patent optimizes the film thickness parameter of the AlN piezoelectric film to a specific range (500nm-2000nm) to achieve high electromechanical coupling coefficient while maintaining acceptable electrode resistance and insertion loss characteristics
3Reliability
If complex control processes are applied to improve piezoelectric film orientation and thickness ratios, then the electromechanical coupling coefficient is improved, but the device complexity increases
Solution Approach 1:
The patent achieves high electromechanical coupling coefficient by controlling the film thickness parameter within a specific range, avoiding the need for complex orientation control processes and reducing overall device complexity
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 effectively increases the electromechanical coupling coefficient while maintaining stable resonant characteristics and preventing excessive insertion loss, allowing for the creation of high-frequency filters with improved performance.
Implementation Method 1
a high-frequency electric signal is supplied between the upper electrode and the lower electrode, so as to excite an elastic wave in the piezoelectric film by virtue of an inverse piezoelectric effect
Implementation Method 2
due to a piezoelectric effect, the distortion caused by the elastic wave is converted into an electric signal
Implementation Method 3
This elastic wave is totally reflected by the faces of the upper electrode and the lower electrode in contact with the air
Implementation Method 4
Resonance is caused at such a frequency that the total film thickness H of the upper electrode, the piezoelectric film, and the lower electrode is an integral multiple (n times) of 1⁄2 of the wavelength of the elastic wave
Data Source
AI summary
A piezoelectric thin-film resonator includes: a lower electrode that is formed on a substrate; a piezoelectric film that is formed on the lower electrode; and an upper electrode that is formed on the piezoelectric film. In the piezoelectric thin-film resonator, the upper electrode has a greater film thickness than the lower electrode.