Experimental and simulation study of the program efficiency of HfO2 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.