Rapid corona charging and stability of positive charge stored in SiO/sub 2//Si/sub 3/N/sub 4/ electrets

A charging procedure combined with a HMDS- and a heat-treatment of the SiO/sub 2//Si/sub 3/N/sub 4/ 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/spl deg/C, which is important for its packaging or use at elevated temperatures.