Wet oxidation of nitride layer implanted with low-energy Si ions for improved oxide-nitride-oxide memory stacks

Abstract

An alternative method for the formation of the top oxide in oxide-nitride-oxide dielectric stacks is proposed. This method combines low-energy (1keV) silicon ion implantation into a thin nitride-oxide stack and subsequent low-temperature wet oxidation (850°C for 15min). Transmission electron microscopy shows that for an implanted dose of 1.5×1016Sicm−2, an 8-nm-thick silicon oxide layer develops on the surface of the nitride-oxide stack. Time of flight secondary ion mass spectrometry reveals: (1) transformation of the implanted silicon nitride to an oxygen-rich-silicon nitride layer and (2) pilling up of nitrogen atoms at the bottom silicon/oxide-substrate interface. The resulting oxide-nitride-oxide stack exhibits strong charge storage effects and excellent charge retention properties leading to a 1.5V, 10yr extrapolated memory window at 125°C. These results suggest that the proposed fabrication route may lead to gate dielectric stacks of substantial potential impact for mainstream nitride-based memory devices.