Modeling of zero TCF and maximum bandwidth orientation for Lithium Tantalate RF MEMS resonators

This work presents an elaborate analytical analysis and finite element geometry modeling to investigate the Temperature Coefficient of Frequency (TCF) and resonator bandwidth (BW) for different orientations and modes of operation in Lithium Tantalate (LT) MEMS resonators. Optimum cut algorithm is used to find the ideal wafer orientation and the proposed algorithm is cross-verified using Finite Element Method. Length extension mode resonators operating in the fundamental mode transcend the performance of contour mode resonators. LT resonators with a wafer orientation of (90°, 41°, 60°) operating in the fundamental length extension mode yield close to zero TCF and when oriented along (90°, 44°, 60°) it provides a maximum BW of 2.67%. Best values of both BW and TCF can be achieved simultaneously in a very close range of wafer orientation.