Effects of gate material on Fowler-Nordheim stress induced thin silicon dioxide degradation under negative gate bias

Abstract

An exhaustive theoretical investigation on the role of gate material as well as commonly used metal deposition processes [viz., electron beam (e-beam) evaporation and thermal evaporation] on high-field stress-induced dielectric breakdown and∕or degradation of identically thick (8–10nm) thermally grown silicon dioxide (SiO2) films used in memory devices has been reported. Gate materials studied here are n+-polycrystalline silicon (polySi) and aluminum (Al) with n-channel metal-oxide-semiconductor field effect transistor structures. Results will be shown here during constant current and constant field Fowler-Nordheim (FN) tunnel injection from the gate into SiO2. Our theoretical results establish that Al-gated structures exhibit poorer dielectric integrity compared to polySi-gated structures under both types of FN stressing technique. Furthermore, compared to thermally deposited Al-gated samples, e-beam evaporated Al-gated samples show slightly higher gate oxide deterioration in either mode of FN stressing studied here.