Near-Carrier Phase Noise Suppression at Turnover Temperature in a Thin-Film Piezoelectric-on-Silicon Oscillator

In this paper, the near-carrier enhancement of phase-noise (PN) at turnover temperature (T-to) in a quasi-thickness-Lame (QTL) mode thin-film piezoelectric-on-silicon (TPoS) oscillator is reported for the first time. QTL-TPoS resonators fabricated on degenerately-doped n-type silicon offer a T-to greater than 80 degrees C and are suitable for implementation of highly-stable ovenized oscillators. In this work, a similar to 123MHz QTL-TPoS resonator is heated up to T-to (similar to 90 degrees C) by injecting current through the silicon body of the resonator. It is experimentally observed that at turnover temperature, the phase-noise slope close to the carrier frequency (Delta f < 100Hz) decreases substantially in contrast to the expected trends. A similar to 10dB improvement in phase noise at 10Hz offset and a similar to 25dB improvement at 1Hz offset is recorded when the oscillator is operating at T-to compared to room temperature. [2020-0206]