Simulation Study of the Trapping Properties of -Based Charge-Trap Memory Cells

In this paper, the trapping properties of HfO₂-based charge-trap cells have been extensively studied by means of a synergic use of material analysis, electrical characterization, and electrical and atomistic modeling. We assessed the impact of process conditions [i.e., postdeposition annealing (PDA)] on the material structure and the trapping behavior of the fabricated gate-stacks. Furthermore, we present reliable models for the HfO₂ structure and for the defects responsible for the electron trapping. We found that HfO₂ has a trap density comparable with that of SiN that depends on the PDA temperature. The HfO₂ traps are shallower in energy than SiN traps, but retention of memory cells is still sufficient, also because of a slightly larger electron affinity and a larger permittivity than SiN that allows thicker layers while preserving the equivalent oxide thickness of the gate-stack.