Acoustic Wave IDT Electrode Layout for Etching Stability
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Solution Overview
Problem
In acoustic wave devices, the etching process for creating void portions can lead to corrosion of IDT electrodes, compromising the stability of electrical characteristics.
Innovation Solution
The acoustic wave device is designed with a cavity portion where the IDT electrodes are located, featuring a through hole in the piezoelectric layer that extends to the cavity, and a dimensional relationship where electrode finger portions closer to the through hole have a smaller thickness and larger width, stabilizing electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the IDT electrode is provided in the void portion, then the device can achieve compact integration, but the etching process causes corrosion of the electrode finger, deteriorating electrical characteristics stability
Solution Approach 1:
The electrode finger is designed with non-uniform thickness, where the thickness varies along the length of the electrode finger. Specifically, the thickness is greater at portions closer to the through-hole and smaller at portions farther away. This local variation in quality compensates for the differential etching effects, maintaining uniform electrical characteristics throughout the electrode finger despite the corrosive etching environment.
Solution Approach 2:
The invention changes the physical parameter of the electrode finger (thickness) to compensate for the harmful etching effects. By adjusting the thickness distribution along the electrode finger length, the design accounts for the varying degree of corrosion that occurs during the etching process, ensuring that the final electrode maintains stable electrical characteristics after fabrication.
2Ease of manufacture
If uniform thickness electrode fingers are used, then manufacturing is simpler, but etching causes non-uniform corrosion, degrading electrical performance
Solution Approach 1:
The electrode finger is designed with non-uniform thickness, where the thickness varies along the length of the electrode finger. Specifically, the thickness is greater at portions closer to the through-hole and smaller at portions farther away. This local variation in quality compensates for the differential etching effects, maintaining uniform electrical characteristics throughout the electrode finger despite the corrosive etching environment.
Solution Approach 2:
The non-uniform thickness distribution is designed in advance to counteract the expected etching effects. By pre-compensating for the corrosion that will occur during the etching process, the electrode finger is designed to achieve uniform final dimensions after etching, rather than starting with uniform dimensions and accepting non-uniform results.
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 ensures stable electrical characteristics by maintaining a constant cross-sectional area of electrode finger portions and preventing electrode damage during etching, thereby enhancing the device's performance.
Implementation Method 1
a piezoelectric layer on the support portion and including a first main surface located on a support portion side and a second main surface opposing the first main surface
Data Source
AI summary
An acoustic wave device includes a support portion, a piezoelectric layer on the support portion and including a first main surface on a support portion side and a second main surface opposing the first main surface, and at least one IDT on the first main surface of the piezoelectric layer and including electrode finger portions. A cavity portion surrounded by the support portion and the piezoelectric layer is provided. The electrode finger portions of the at least one IDT are located in the cavity portion. At least a portion of an electrode finger portion of the IDT at a position closer to the through hole in one set of the electrode finger portions has a smaller thickness and a larger width than at least a portion of an electrode finger portion at a position farther from the through hole.