Ald Titania Sidewalls On A Cmos-Mems Resonator Oscillator And Effects On Resonant Frequency Drift

A lift-off patterned atomic layer deposition (ALD) process that selectively coats CMOS MEMS sidewalls with conductive titania (TiO2) effectively eliminates the effects of dielectric sidewall charging. Charging effects are quantified through measurement of resonant frequency drift in a CMOS MEMS resonator oscillator with and without the titania coating. The coating drastically lowers the charging time constant to less than the 1 s frequency counter measurement period, compared to the long-term distributed time constant on the order of hours seen in uncoated devices and arising from trap behavior.