Impact of Nonuniform Doping on Random Telegraph Noise in Flash Memory Devices

Abstract

This paper presents a thorough numerical investigation of the effect of nonuniform doping on random telegraph noise (RTN) in nanoscale Flash memory devices. For a fixed average threshold voltage, the statistical distribution of the RTN fluctuation amplitude is studied with nonconstant doping concentrations in the length, width, or depth direction in the channel, showing that doping increase at the active area corners and retrograde and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\delta$</tex></formula> -shape dopings appear as the most promising profiles for RTN suppression. In particular, the improvements offered by retrograde and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \delta$</tex></formula> -shape dopings increase the more the high doping regions are pushed far from the channel surface due to a more uniform source-to-drain conduction during read. Finally, the suppression of RTN by engineered doping profiles is correlated with the reduction in cell threshold voltage variability.