BAW Resonator Top Electrode Connection With Air-Gap Capping
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Solution Overview
Problem
BAW resonators face challenges in optimizing lateral design to suppress acoustic energy leakage, requiring different features for various electrode connection configurations, which leads to trade-offs between acoustic and electromagnetic performance and compromises in filter performance.
Innovation Solution
A BAW resonator design with a top electrode connection arranged above a capping layer and a conductive spacer, minimizing the impact on acoustic modes, allowing for a single symmetric lateral design and reduced ohmic losses, achieved through a spacer and capping layer structure with an air-filled gap and conductive path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different lateral features are applied to suppress acoustic energy leakage in different regions, then acoustic performance is improved, but device complexity increases
Solution Approach 1:
The patent applies different lateral features to different regions of the resonator: a first lateral feature (acoustic reflector) is applied in the first region where the top electrode is connected, while a second lateral feature (acoustic absorber or different reflector) is applied in the second region where the bottom electrode is connected. This local differentiation optimizes acoustic performance for each connection type without requiring a completely different resonator design.
2Ease of manufacture
If the top electrode connection is arranged in the plane of the top electrode, then manufacturing is simplified, but acoustic energy leakage increases
Solution Approach 1:
The top electrode connection is moved from the plane of the top electrode to a different plane (typically the substrate plane or a plane below the piezoelectric layer). This dimensional relocation allows the connection to be made without interfering with the acoustic field in the piezoelectric layer, thereby reducing acoustic energy leakage while still being manufacturable through standard semiconductor processing techniques.
3Reliability
If the resonator is optimized for low acoustic loss, then acoustic performance is improved, but electromagnetic loss increases
Solution Approach 1:
The patent optimizes different regions of the resonator for different performance criteria: regions with top electrode connections are optimized for electromagnetic performance with appropriate lateral features, while regions with bottom electrode connections are optimized for acoustic performance. This local optimization allows the overall resonator to achieve both low acoustic loss and low electromagnetic loss without requiring a single compromise design.
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 reduces the complexity of lateral design optimization to a single configuration, enabling reduced chip size and lower ohmic losses while maintaining high power durability and efficient acoustic performance.
Implementation Method 1
a piezoelectric layer and a top electrode
Data Source
AI summary
A BAW resonator comprises a bottom electrode, a piezoelectric layer and a top electrode. A top electrode connection is arranged in a plane above the top electrode. For doing this a spacer is arranged on the top electrode. A capping layer is sitting on the spacer distant from the top electrode such that an air-filled gap to the top electrode is kept. The top electrode connection can now be arranged above the capping layer. An electrically conductive path connects the top electrode and the top electrode connection. Such a resonator needs only one lateral design and can provide a low-ohmic interconnection of resonators e.g. in a filter circuit.