IDT Electrode Gap Structure to Suppress Acoustic Wave Distortion
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Solution Overview
Problem
Conventional acoustic wave devices experience degraded electrical characteristics due to distorted waves caused by electric fields generated in gaps between IDT electrodes, leading to a decrease in electromechanical coupling coefficients.
Innovation Solution
The acoustic wave device incorporates a design with convex portions on the busbar electrodes and electrode fingers projecting towards gaps, reducing the gap distance and incorporating hollow portions to minimize the electric field intensity, thereby preventing distorted waves and maintaining device characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the thickness of the insulation film is increased to concentrate electric fields and reduce the electric field generated in the gap, then the distorted wave is suppressed, but the electromechanical coupling coefficient decreases and the characteristics of the acoustic wave device degrade
Solution Approach 1:
The invention applies local quality by providing convex portions only at specific locations (busbar electrodes and/or electrode fingers) rather than uniformly increasing insulation film thickness across the entire device. This localized structural modification concentrates the electric field reduction effect where it is most needed (in the gap region) while preserving the electromechanical coupling properties in other critical regions of the piezoelectric substrate.
Solution Approach 2:
The invention transitions from a two-dimensional planar structure to a three-dimensional structure by adding convex portions that protrude into the gap region. This dimensional change allows the electrodes to physically reduce the gap distance and modify the electric field distribution in a way that cannot be achieved by simply increasing film thickness in the original plane.
2Ease of manufacture
If conventional IDT electrode design is used with uniform gap spacing, then manufacturing is simple, but electric field concentration causes distorted waves and electrical characteristic degradation
Solution Approach 1:
The convex portions are implemented using standard photolithography and etching processes that can be integrated into existing manufacturing workflows. The local modification approach maintains compatibility with conventional fabrication techniques while achieving the desired electric field control, thus not 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 the electric field intensity in the gaps, preventing distorted waves and preserving the acoustic wave device's performance by minimizing the impact on electromechanical coupling coefficients.
Implementation Method 1
At least one of an opposing surface of the busbar electrode and an opposing surface of the electrode finger, the opposing surfaces being opposed to each other with the gap therebetween, includes a convex portion projecting toward the gap side from a portion separated from the piezoelectric substrate such that a distance of the gap is shorter at the portion separated from the piezoelectric substrate compared to at a portion in contact with the piezoelectric substrate. A hollow portion exists between the convex portion and the piezoelectric substrate.
Implementation Method 2
a piezoelectric substrate and an IDT electrode on the piezoelectric substrate
Data Source
AI summary
An IDT electrode includes first and second busbar electrodes opposed to each other, first and second electrode fingers extending respectively from the first and second busbar electrodes on a piezoelectric substrate. The first busbar electrode and a tip end of the second electrode finger are opposed to each other with a gap therebetween, and bottom surfaces of the first and second busbar electrodes are opposed to each other with a first gap therebetween. The first and second busbar electrodes respectively include portions opposed to each other with a second gap shorter than the first gap therebetween on the top surface side. In a first area located between a first side surface and a second side surface, a second area located between the piezoelectric substrate and the first busbar electrode or the second electrode finger includes a hollow portion.