Advancing Precision Timing: A Thermally Stable Lithium Tantalate MEMS Oscillator with low Phase Noise

This study presents a micro-electromechanical system (MEMS) oscillator built using a Lamb wave resonator fabricated on X-cut Lithium Tantalate (LT). Leveraging the unique anisotropic characteristics of LT and by adjusting the resonator’s geometry and orientation, the turnover temperature (ToT) was tailored to occur beyond 85 deg C which is crucial for development of micro-oven-controlled oscillators with superior temperature stability and low phase-noise. Through finite element analysis (FEA), it was identified that reducing the resonator’s length-to-width ratio could increase the ToT, particularly in orientations between 30° and 45° off the Y-axis of X-cut LT. Based on these FEA insights, a 283 MHz Lamb wave resonator with a 35° off Y-axis configuration was fabricated and integrated within a low-power oscillator circuit. The oscillator exhibited a ToT exceeding 90°C and low phase noise performance. These findings underscore the potential of thin-film LT resonators as miniaturized counterpart to conventional quartz crystal oscillators for ultra-stable, ovenized clock applications.