Thickness-Governed Piezoelectric Constants and Electromechan ICAL Coupling Coefficient in AlN Thin Film

Aluminum nitride (AlN) piezoelectric films are widely utilized in MEMS, acoustic wave devices, and energy harvesting applications due to their exceptional piezoelectric properties, excellent chemical stability, and superior semiconductor process compatibility. Although device performance is critically determined by film thickness through modulation of piezoelectric response, electromechanical coupling coefficient, and residual stress distribution, systematic investigations of thickness-dependent behavior remain limited. In this study, a multiphysics simulation approach combining 3D electromagnetic-acoustic coupling in ANSYS HFSS with piezoelectric constitutive modeling is presented. The correlation between AlN film thickness (300-2000 nm) and key performance metrics is quantitatively established through controlled parametric analysis. A non-monotonic relationship is revealed, where optimal piezoelectric constants (5.5-6.0 pC/N) are maintained across the 100-2000 nm range, while maximum electromechanical coupling (6.1-6.8%) is observed at thinner dimensions (100-1000 nm). These findings establish design rules for AlN-based devices, particularly for 5G RF filters and piezoelectric MEMS where thickness optimization is crucial.