Improved TCF of Low Velocity LN HAL SAW Resonators using Glass Substrate

The combination of lithium niobate (LN), quartz (Qz) and copper (Cu) interdigital-transducers (IDTs) has produced a Hetero Acoustic Layer (HAL) surface acoustic wave (SAW) resonator with low phase velocity, high impedance ratio (Z-ratio), large relative bandwidth (BW), and low spurious responses. However, the use of LN and Qz substrates with negative temperature coefficient of frequency (TCF) rotated angle have resulted in large TCF. In this study, the combination of 11°YX LN and a glass substrate with low coefficient of linear thermal expansion was fabricated. The resulting LN HAL SAW resonator has shown a decrease of roughly 45% in TCF with a trade-off of Z-ratio.