“…In addition to traditional quartz resonator-based reference oscillators (Vittoz et al, 1988) and quartz crystal microbalance (QCM) sensors (Ferrari et al, 2006), miniaturized oscillators using microelectromechanical systems (MEMS) technology have been intensively studied in both academia and industry over the past two decades (Lavasani et al, 2011;Chance et al, 2014;Zaliasl et al, 2015;Naing et al, 2020;Kalia et al, 2021;Chang et al, 2022) to be used in demanding applications with size constraints. Among the existing MEMS oscillator fabrication approaches, the CMOS-MEMS technology is one of the most promising approaches to achieving the monolithic integration of mechanical resonators and electronic circuits (Xie et al, 2002;Dai et al, 2005;Chen et al, 2011;Li C.-S. et al, 2012;Chen et al, 2019;Valle et al, 2021). In this approach, MEMS mechanical structures can be formed from the back-end of line (BEOL) metal/dielectric (Verd et al, 2006;Li et al, 2012c;Li et al, 2015b;Liu et al, 2018) or the front-end of line (FEOL) polysilicon layers (Verd et al, 2005;Lopez et al, 2009) by removing predefined sacrificial layers, thereby eliminating the thermal budget constraints that are often encountered in other custom IC-MEMS integration processes (Fedder et al, 2008).…”