Comprehensive Investigation of Statistical Effects in Nitride Memories—Part II: Scaling Analysis and Impact on Device Performance

Abstract

This paper presents a scaling analysis of the statistical distribution of the threshold voltage shift <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(\Delta V_{T})$</tex></formula> obtained by electron storage in nitride memories, considering both its average and standard deviation. For fixed density of trapped charge, the average <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\Delta V_{T}$</tex></formula> decreases as a consequence of fringing fields, not predictable by any 1-D simulation approach. Moreover, the distribution statistical dispersion increases with technology scaling due to a more sensitive percolative substrate conduction in the presence of atomistic doping and 3-D electrostatics. The impact of these effects on device performance is then highlighted, showing that the accuracy of the staircase programming algorithm can be reduced further from the limitation given by the electron injection statistics during programming. The impact of electron storage in the nitride on random telegraph noise instabilities is also investigated, showing that, despite single cell behavior may be modified, negligible effects result at the statistical level.