Effect of surface conduction on dielectric charging in RF MEMS capacitive switches

Charging of the surface of the dielectric in electrostatically actuated RF MEMS capacitive switches has been shown to be strongly affected by ambient humidity. We now hypothesize that the humidity affects surface charging through enhanced surface conduction. This is confirmed by the experimental results obtained on surface conductivity sensors and RF MEMS capacitive switches fabricated on the same die. The results suggest that it is critical to not only minimize the humidity in the switch package, but also optimize the surface chemistry of the switch dielectric to reduce its surface conductivity.