Effects of different Si3N4 thicknesses on the performance of PECVD SiO2/Si3N4 double layers electrets

In this paper, charge decay of PECVD SiO₂/Si₃N₄ double layers electrets with different thicknesses of Si₃N₄ under different environmental conditions was investigated. Single layers of PECVD prepared SiO₂ and Si₃N₄ were also studied. Double layers electrets exhibits better charge stability than single layer under different conditions. As for the double layers with 2 nm-100 nm Si₃N₄, their charge stability at 250°C is as good as each other. However, if the Si₃N₄ thickness continues to increase, the charge stability will be decreased. Thicker layer of Si₃N₄ leads to better charge stability under 95%RH. Heat treatment at 250°C can improve charge stability under high humidity condition, especially for double layers electrets with thin Si₃N₄. After heat treatment at 250°C for 3hrs, the PECVD SiO₂/Si₃N₄ double layers electrets with 50 nm Si₃N₄ show the optimized charge stability under different conditions.