Temperature-compensated aluminum nitride lamb wave resonators

In this paper, the temperature compensation of AlN Lamb wave resonators using edge-type reflectors is theoretically studied and experimentally demonstrated. By adding a compensating layer of SiO₂ with an appropriate thickness, a Lamb wave resonator based on a stack of AlN and SiO₂ layers can achieve a zero first-order temperature coefficient of frequency (TCF). Using a composite membrane consisting of 1 ??m AlN and 0.83 ??m SiO₂, a Lamb wave resonator operating at 711 MHz exhibits a first-order TCF of -0.31 ppm/??C and a second-order TCF of -22.3 ppb/??C² at room temperature. The temperature-dependent fractional frequency variation is less than 250 ppm over a wide temperature range from -55??C to 125??C. This temperature-compensated AlN Lamb wave resonator is promising for future applications including thermally stable oscillators, filters, and sensors.