Effect of the trap density and distribution of the silicon nitride layer on the retention characteristics of charge trap flash memory devices

Abstract

The trap distribution in the silicon-nitride layer, which was estimated by using experimental results, was used to clarify the retention characteristics of TaN-Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> -SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -Si (TANOS) memory devices. The dependence of the trap density and distribution of the silicon nitride layer on the retention characteristics in TANOS memory devices was investigated by using the two-coupled rate equations together with the Shockley- Reed statistics. Simulation results showed that the retention characteristics in TANOS memory devices increased with increasing trap density near and above the Fermi-level in the silicon-nitride layer. The simulation results for the retention characteristics of TANOS memory devices were in reasonable agreement with the experimental results. These observations can help improve understanding of the retention mechanisms and the reliability problems in charge trap flash (CTF) memory devices.