Sidewall Metallization on CMOS MEMS by Platinum ALD Patterning

Patterned atomic layer deposition (ALD) that selectively coats sidewalls with platinum (Pt) is developed to improve performance on CMOS MEMS devices. The proposed fabrication process is the first, to our knowledge, to pattern metal ALD on high-aspect-ratio MEMS sidewalls. A reflow step for the lift-off resist is introduced to increase yield by solving stringer issues. Sidewall metallization enables higher sensitivity on capacitive sensors and eliminates dielectric charging. A Pt-coated resonator oscillator and a capacitive accelerometer are demonstrated as examples, showing the successful process results. The measurement on a Pt-coated resonator oscillator indicates much higher stability than with the original dielectric sidewalls. This metal sidewall coating also has potential for other CMOS MEMS devices, such as switches. [2020-0178]