167-MHz AlN Capacitive-Piezoelectric Oscillator

This work constitutes a first demonstration of a closed-loop oscillator referenced to a 20.4-μm-radius high-Q radial-contour mode AlN capacitive-piezoelectric resonator that posts a measured phase noise of -87 dBc/Hz at 1-kHz offset from its 167.3-MHz carrier while consuming only 173 μW to achieve an oscillator Figure of Merit (FoM) of -199.1 dBc/Hz. The key enablers of this demonstration are the 200-nm and 125-nm top and bottom electrode-to-resonator gaps, respectively, that define this resonator type and that not only enable high Q by eliminating electrode-to-resonator strain loss but are also small enough to retain high electric fields within the AlN that provide 0.3% electromechanical coupling sufficient for self-sustained oscillation in a Pierce circuit using very little power drain.