Curved Top Electrode Layout for Crack-Resistant BAW Resonators
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Solution Overview
Problem
Existing bulk acoustic wave filters are prone to cracking during chemical mechanical polish due to sharp corners, leading to stress concentration and invalidation of device properties.
Innovation Solution
A bulk acoustic wave resonator and filter design featuring a top electrode with an outline formed by end-to-end connected curves, with arc transitions at joints and non-parallel arrangements, preventing sharp corners and reducing stress concentration, thereby enhancing device reliability and Q value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a sharp corner shape is used for the electrode, then the manufacturing process is simple, but cracking occurs during chemical mechanical polish and stress concentration is caused
Solution Approach 1:
The patent applies curvature by replacing sharp corners with arc transitions in the electrode outline. The specification states that 'arc transition is set at a joint of every two adjacent curves' to eliminate sharp corners, which prevents cracking during chemical mechanical polishing and reduces stress concentration, thereby improving device reliability while maintaining manufacturing feasibility.
2Reliability
If arc transition is set at joints of curves, then cracking is prevented and stress concentration is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent uses arc transitions at curve joints to eliminate sharp corners, which prevents cracking during chemical mechanical polishing and reduces stress concentration, thereby improving device reliability while maintaining manufacturing feasibility.
Solution Approach 2:
The patent employs non-parallel curve arrangements where 'every two curves arranged in a spaced manner are not parallel'. This asymmetric design disrupts parasitic resonance paths while maintaining structural integrity, balancing improved reliability with controlled manufacturing complexity.
3Device complexity
If parallel curves are used, then the design is simple, but parasitic resonance occurs and Q value decreases
Solution Approach 1:
The patent employs non-parallel curve arrangements where 'every two curves arranged in a spaced manner are not parallel'. This asymmetric design disrupts parasitic resonance paths by preventing symmetric standing wave formation, thereby reducing energy loss and improving the Q value of the resonator.
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
The design effectively improves the reliability and performance of bulk acoustic wave devices by preventing cracking and reducing parasitic resonance amplitude, resulting in improved device properties and increased Q value.
Implementation Method 1
A bulk acoustic wave filter utilizes a piezoelectric effect of piezoelectric crystals for generating resonance
Data Source
AI summary
This application provides a bulk acoustic wave resonator and a bulk acoustic wave filter, and relates to the technical field of filters. The bulk acoustic wave resonator includes a substrate, and a bottom electrode, a piezoelectric layer, a top electrode which are sequentially stacked on the substrate, and an outline of an orthographic projection of the top electrode on the substrate is formed by four curves which are end-to-end connected. Arc transition is set at a joint of every two adjacent curves, and every two curves arranged in a spaced manner are not parallel. Accordingly, reliability of devices can be effectively improved, meanwhile, parasitic resonance amplitude can be effectively restrained, a Q value is increased, and thus device properties are improved.