Acoustic Wave Resonator Cavity Gap Optimization

The cavity is designed with non-uniform gap distribution, where the gap between the resonating part and substrate varies at different locations. Specifically, the gap is smaller at the center and larger at the edges, creating local quality variations that optimize both miniaturization and resonance performance. This local quality approach allows the resonator to maintain high Q-factor and bandwidth while achieving compact size.

The membrane layer thickness is precisely controlled within a specific range (50-200 nm) to optimize the balance between miniaturization and resonance performance. This parameter optimization ensures that the membrane is thin enough for compact device dimensions while maintaining sufficient mechanical strength and acoustic resonance characteristics. The thickness parameter is tuned to achieve desired resonant frequencies and quality factors.

The resonator structure is segmented into distinct functional layers including the substrate, cavity layer with etch stop layer, resonating part with multiple functional films (buffer layer, piezoelectric layer, electrode layers), and overlying structures. This segmentation allows each layer to be optimized for its specific function while maintaining manufacturability through standard thin-film deposition and patterning techniques. The piezoelectric layer is further segmented into multiple sub-layers with different orientations to enhance electromechanical coupling.

The resonator utilizes the vertical dimension by creating a suspended cavity structure that extends the resonating volume in the thickness direction without increasing the planar footprint. The cavity depth and gap variations in the vertical dimension provide additional degrees of freedom for optimizing resonance characteristics, allowing high Q-factor and bandwidth to be achieved within a compact lateral area. This three-dimensional structuring enables performance enhancement without sacrificing miniaturization.