Acoustic Wave Cavity Sidewall Geometry to Prevent Cracks and Sticking
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Solution Overview
Problem
Conventional acoustic wave devices often experience cracks in the dielectric film and sticking of the piezoelectric layer to the dielectric film, leading to deterioration of electrical characteristics.
Innovation Solution
The acoustic wave device incorporates a support substrate with a dielectric film and a piezoelectric layer, featuring a cavity portion in the dielectric film where the side wall surface has an inclined portion that decreases in width with distance from the piezoelectric layer, with an inclination angle between 40° to 80°, reducing crack generation and sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cavity portion is formed in the dielectric film, then electrical characteristics are improved, but cracks are generated in the dielectric film and the piezoelectric layer sticks to the dielectric film
Solution Approach 1:
The side wall surface of the cavity portion is formed with an inclined portion that has a curved or angled surface rather than a vertical wall. The inclination angle of 40° to 80° creates a tapered geometry that eliminates stress concentration points, preventing cracks in the dielectric film and preventing the piezoelectric layer from sticking to the dielectric film while maintaining the cavity's electrical performance benefits
2Ease of manufacture
If the cavity portion has a vertical side wall, then manufacturing is simpler, but stress concentration causes cracks and sticking
Solution Approach 1:
The geometry parameter of the cavity side wall is changed from vertical (90°) to an inclined angle of 40° to 80°. This parameter modification redistributes mechanical stress uniformly across the cavity walls, eliminating stress concentration that would cause cracks and sticking, while the inclined portion can still be formed using standard semiconductor manufacturing techniques
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 effectively reduces or prevents cracks in the dielectric film and sticking of the piezoelectric layer, thereby improving the electrical characteristics and reliability of the acoustic wave device.
Implementation Method 1
a piezoelectric layer (14) on the dielectric film (13)
Data Source
AI summary
An acoustic wave device includes a support substrate, a dielectric film, a piezoelectric layer, and an excitation electrode. The piezoelectric layer includes first and second main surfaces. The second main surface is on a side including the dielectric film. A cavity portion is provided in the dielectric film and overlaps at least a portion of the excitation electrode in plan view. The dielectric film includes a side wall surface facing the cavity portion and including an inclined portion inclined so that a width of the cavity portion decreases with increasing distance away from the piezoelectric layer. The inclined portion includes at least an end portion on a side including the piezoelectric layer, in the side wall surface. When an angle between the inclined portion and the second main surface of the piezoelectric layer is defined as an inclination angle α, the inclination angle α is from about 40° to about 80° inclusive.