Temperature accelerated discharging processes through the bulk of PECVD silicon nitride films for MEMS capacitive switches

Abstract

The effect of temperature on discharging processes of PECVD silicon nitride films has been investigated in Metal-Insulator-Metal (MIM) capacitors and RF MEMS capacitive switches with the aid of Kelvin Probe method. The surface potential decay of MIM capacitors during discharge has been monitored using a Single-point Kelvin probe system at various temperatures (300K–400K) while the shift of bias at minimum up-state capacitance during discharge has been employed in MEMS capacitive switches in order to determine the discharge current through the bulk of the film at different temperatures. The results indicate that the discharging process through the bulk of silicon nitride films is thermally activated and the corresponding value of the discharging current increases with temperature, due to the increase of the film conductivity. Moreover, the value of minimum up-state capacitance of the switches is found to be significantly affected by temperature, by the mechanical properties of the moving armature as well as by the variance of charge density distribution. Finally, different thermally activated mechanisms have been observed in MIM capacitors and MEMS capacitive switches, due to different charging processes on these devices.