Evaluation of the Impact of Abnormally Orientated Grains on the Performance of ScAlN-based Laterally Coupled Alternating Thickness (LCAT) Mode Resonators and Lamb Wave Mode Resonators

Abnormally oriented grains (AOGs) widely exist in the Sc doped AlN films, especially for Sc concentration more than 15%. In this work, the impact of the AOGs on the performance of ScAlN-based laterally coupled alternating thickness (LCAT) mode resonators and Lamb wave mode resonators are systematically evaluated by FEM modelling. The correlation between the coupling coefficient of the resonators and the parameters of the AOGs, including density, dimension and crystal orientation, is revealed. The simulations are consistent with the on-wafer device measurement results. This study provides a practical method to estimate the effects of the AOGs and a guideline for the ScAlN film optimization for resonators utilizing the lateral modes.