Temperature Stability Analysis of Thin-Film Lithium Niobate SH0 Plate Wave Resonators

This work presents an extensive study on the temperature coefficient of frequency (TCF) for thin-film lithium niobate (LiNbO
₃
) resonators. To capture the temperature-frequency behavior for each vibration mode, a one-dimensional (1D) multi-section TCF model is proposed and verified by both the finite-element method (FEM) and experiments. By partitioning the metallized and non-metallized sections of the interdigitated transducers (IDT) as distinct TCF blocks and properly considering the spatial energy distribution, the TCF of each mode can be accurately predicted. Two higher lateral-order resonators based on the fundamental shear-horizontal mode (SH
₀
) are designed and fabricated on a LiNbO
₃
-on-SiO
₂
wafer to provide odd- and even-order harmonics. TCFs of the first 6 overtones (from 84 to 515 MHz) are calculated using the material properties given in the literature, exhibiting a maximum TCF difference of 3 ppm/K between the theoretical prediction and measurement results. Although only SH
₀
resonators are selected for experimental verification, the proposed multi-section TCF model can be applied to other plate wave MEMS resonators. [2019-0112].