Segmented Acoustic Resonator Layout for Stable TCF
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Solution Overview
Problem
In acoustic wave devices with multiple resonators on a common substrate, temperature differences across resonators with different frequency bands can lead to temperature coefficient of frequency (TCF) degradation due to local deformation of the piezoelectric thin film, affecting device performance.
Innovation Solution
The acoustic wave device features separate resonant sections with piezoelectric thin films divided by a support layer having a different linear expansion coefficient, reducing thermal deformation and improving TCF characteristics by isolating temperature effects between adjacent sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple acoustic wave resonators are provided on a common piezoelectric thin film, then the device can perform multiband communication, but temperature distribution causes local deformation of the piezoelectric thin film and degrades TCF characteristics
Solution Approach 1:
The common piezoelectric thin film is divided into multiple independent regions, each serving a specific resonator. This segmentation prevents temperature distribution from causing cumulative deformation across the entire film, as each segment can be independently managed. The support layer further divides these piezoelectric thin films, ensuring that thermal deformation in one resonator does not affect adjacent resonators, thus maintaining stable TCF characteristics while enabling multiband communication.
Solution Approach 2:
Each piezoelectric thin film region is optimized for its specific resonator's frequency band and thermal characteristics. By providing individual support layers for each resonator, the structure allows localized thermal management, where each region can handle its own temperature variations independently. This local quality approach ensures that TCF characteristics remain stable for each frequency band without being compromised by temperature distribution across the entire device.
2Device complexity
If a common piezoelectric thin film is used for multiple resonators, then the device structure is simplified, but thermal deformation affects adjacent resonant sections and degrades device performance
Solution Approach 1:
The device structure is segmented into multiple independent resonator units, each with its own piezoelectric thin film and support layer. This segmentation maintains relative structural simplicity while preventing thermal deformation from propagating between adjacent resonant sections. Each segment can be manufactured and optimized independently, then integrated into the final device, achieving both structural simplicity and performance stability.
Solution Approach 2:
The support layer acts as an intermediary structure that physically separates and thermally isolates adjacent piezoelectric thin films. This intermediary element prevents direct thermal coupling between resonators while maintaining overall device structural integrity. The support layer's different linear expansion coefficient helps compensate for thermal effects, ensuring stable device performance without significantly increasing manufacturing 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 reduces thermal deformation and enhances the temperature coefficient of frequency (TCF) characteristics, stabilizing the device's performance across varying temperature conditions.
Implementation Method 1
The support layer has a different linear expansion coefficient from the piezoelectric thin film
Implementation Method 2
Each of the first resonant section and the second resonant section includes a piezoelectric thin film, an IDT electrode disposed on the piezoelectric thin film
Data Source
AI summary
An acoustic wave device includes a support substrate and first and second resonant sections adjacent to each other on the support substrate. Each of the first and second resonant sections includes a piezoelectric thin film, an IDT electrode on the piezoelectric thin film, and a support layer surrounding the piezoelectric thin film in a plan view of the acoustic wave device. The support layer has a different linear expansion coefficient from the piezoelectric thin film. The piezoelectric thin film in the first resonant section and the piezoelectric thin film in the second resonant section are divided by the support layer between the resonant section and the resonant section.