Experimental and simulation study of the program efficiency of HfO 2 based charge trapping memories

This work addresses the use of HfO2 as trapping layer in TaN/Al2O3/HfO2/SiO2/Si (TAHOS) stacks for scaled non-volatile memories, by a complete characterization of the physical properties as a function of thermal budget and film thickness and of the program characteristics, with the aim of a benchmarking with the conventional Si3N4 (TANOS). The TAHOS stack withstands high temperature budget (>1000 °C) and shows similar program speed with respect to TANOS devices, thus revealing similar electron injection conditions. Moreover, the high dielectric constant of HfO2 allows for an efficient EOT scaling and/or a large physical thickness for an improved trapping efficiency. Modeling of program transients contributed to the understanding of the trapping in TANOS/TAHOS devices and to the identification of physical processes possibly limiting the gate stack scaling.

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