Mass-Loaded BAW Resonator Structure for High-Frequency Loss Reduction

The patent employs composite material structures including alternating piezoelectric layers (e.g., AlN and ScAlN) with different acoustic properties, mass load layers (e.g., tungsten or molybdenum), and interposer layers. These composite structures are designed to manipulate acoustic wave propagation, reducing acoustic losses at higher frequencies while maintaining the desired resonant frequency response. The different materials provide complementary properties that collectively mitigate the acoustic loss problem.

The patent implements localized mass load layers positioned at specific regions where acoustic energy concentration occurs, and interposer layers placed at strategic positions within the resonator structure. These localized modifications target specific acoustic loss mechanisms without requiring complete structural redesign, thereby reducing acoustic losses while preserving the overall resonator functionality at higher 5G frequencies.

The patent divides the resonator structure into multiple discrete functional layers including piezoelectric layers, mass load layers, and interposer layers. Each layer can be independently optimized and fabricated with standard precision tolerances, avoiding the need for single-layer ultra-precise fabrication. The segmented structure allows higher frequency operation while maintaining relaxed manufacturing precision requirements for individual layers.

The patent utilizes parameter changes in material composition (e.g., varying Scandium content in ScAlN layers) and layer thickness ratios to achieve desired resonant frequencies at higher bands. By adjusting these parameters within standard fabrication capabilities, the patent achieves high-frequency operation without requiring extreme manufacturing precision that would be necessary for uniform scaling of conventional structures.

The patent introduces composite material layers including piezoelectric materials with enhanced coupling coefficients (e.g., ScAlN with optimized Scandium content), mass load layers for improved acoustic confinement, and interposer layers for stress management. These composite structures collectively enhance electromechanical coupling efficiency while adding only moderate structural complexity, achieving better reliability for 5G applications.

The patent incorporates interposer layers as intermediary structures between the piezoelectric layers and electrodes. These interposer layers serve as mediators that improve stress transfer and acoustic wave generation efficiency, thereby enhancing electromechanical coupling. The interposer layers add minimal complexity while providing significant improvement in coupling reliability.