Rapid corona charging and stability of positive charge stored in SiO2/Si3N4 electrets

A charging procedure combined with a HMDS- and a heat-treatment of the SiO₂/Si₃N₄ electret on a silicon carrier is developed. The retention of a positive charge and its re-trapping is investigated. The optimized process parameters provide about 100-year lifetime of the electret. No spatial charge re-trapping is observed at a characteristic length of 0.1 mm after processing of the electret. A set of experiments is carried out to characterize the properties of the electret at temperatures up to 450°C, which is important for its packaging or use at elevated temperatures.