Highly Reliable Trench Capacitor With SiO2/Si3N4/SiO2 Stacked Film

This paper deals with the reliability aspects of trench capacitors with the stacked film of SiO2/Si3N4/Sio2. Trench MOS capacitor shows larger leakage current under positive gate bias compared to plane MOS capacitor, because of the electric field enhancement at Si convex corner. In the case of the stacked film, trapped electrons in Si3N4 relax the electric field near Si corner and suppress the leakage current. The trench MIS capacitor also exhibits higher breakdown voltage of time-zero dielectric breakdown and longer mean time to failure (MTTF) of time dependent dielectric breakdown (TDDB) compared to trench MOS capacitor. Therefore, the stacked film is prominent as an insulator for trench capacitor.