In this paper, the trapping properties of HfO 2 -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 HfO 2 structure and for the defects responsible for the electron trapping. We found that HfO 2 has a trap density comparable with that of SiN that depends on the PDA temperature. The HfO 2 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.
29 Apr 2014
Volume: 61 Issue: 6 Pages: 2056-2063
IEEE Transactions on Electron Devices