Charge storage in APCVD silicon nitride

Silicon nitride is widely used as a dielectric in semiconductor devices or as membrane material in micromachined sensors and actuators. In this paper, preliminary results on investigations of silicon nitride as an electret material are presented. 300 nm layers of Si₃N ₄ were prepared by chemical vapor deposition at atmospheric pressure (APCVD) on silicon wafers of 5 cm diameter at 900°C. The samples were charged positively and negatively by a point to grid corona apparatus. A charge density of up to ±1 μC/cm², depending on the charging polarity, could be achieved. The charge stability was observed by isothermal charge decay at room temperature and at 300°C. Open circuit TSC measurements after different charging steps were carried out and show discharge current peaks at temperatures around 410°C for negatively charged samples