Acoustic Wave Filter With Segmented Dielectric Film
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Solution Overview
Problem
Existing acoustic wave devices face challenges in controlling the electromechanical coupling coefficient, which is crucial for determining the pass band width of filters, due to limitations in the thickness and controllability of dielectric films used in current methods.
Innovation Solution
The acoustic wave device incorporates a piezoelectric substrate with a first dielectric film that is cut out between adjacent electrode fingers, allowing for improved control over the electromechanical coupling coefficient by minimizing its change with film thickness variations, thereby enhancing fabrication process controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a dielectric film is used to control the electromechanical coupling coefficient, then the pass band width can be adjusted, but the controllability is poor due to significant changes in coupling coefficient with film thickness variations
Solution Approach 1:
The dielectric film is segmented (cut out) between adjacent electrode fingers, creating a periodic structure that reduces the sensitivity of the electromechanical coupling coefficient to film thickness variations. This segmentation allows the pass band width to be adjusted while maintaining better manufacturing precision.
Solution Approach 2:
The dielectric film is selectively removed only in specific regions between electrode fingers rather than uniformly across the entire substrate. This local modification creates zones with different dielectric properties that optimize the electromechanical coupling while reducing sensitivity to thickness variations.
2Measurement precision
If the dielectric film thickness is reduced to improve frequency control precision, then manufacturing tolerance becomes more critical and deviations increase
Solution Approach 1:
By segmenting the dielectric film between electrode fingers, the structure reduces the overall impact of film thickness variations on the electromechanical coupling coefficient. This allows for better frequency control precision even with moderate film thickness tolerances.
Solution Approach 2:
The segmented dielectric film structure acts as an intermediary that decouples the relationship between film thickness and electromechanical coupling coefficient. This intermediary structure reduces the direct sensitivity, allowing frequency control without requiring extremely tight thickness tolerances.
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 configuration provides better controllability of the electromechanical coupling coefficient and film thickness, leading to more precise frequency control and reduced deviations during the fabrication process, resulting in improved filter performance.
Implementation Method 1
When electric power is applied across the comb electrodes, a surface acoustic wave is excited
Implementation Method 2
a surface acoustic wave is excited
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate, a first dielectric film formed on the piezoelectric substrate, and electrodes that are provided on the first dielectric film and excite an acoustic wave, the electrodes including electrode fingers. At least a part of the first dielectric film is cut out between adjacent electrode fingers among the electrode fingers.