Metal microelectromechanical oscillator exhibiting ultra-high water vapor resolution

Water vapor sensing characterization of a metal resonator fabricated with an industrial 0.35 μm CMOS technology is reported. The resonator frequency is ∼13.2 MHz and exhibits a sensitivity magnitude of ∼3.5 kHz per %RH without requiring any additional hygroscopic coating layer. An on-chip integrated oscillator circuit enables an unprecedented resolution of 0.005 %RH.