Multi-level 2-bit/cell operation utilizing Hf-based metal/oxide/nitride/oxide/silicon nonvolatile memory with HfO 2 and HfON tunneling layer

This paper investigated the multi-level 2-bit/cell operation utilizing a Hf-based metal/oxide/nitride/oxide/silicon (MONOS) nonvolatile memory (NVM) device with a HfO 2 and HfON tunneling layer (TL). The 2-bit/cell operation is realized by utilizing the localized charge injection method. It was found that drain-current–gate-voltage ( I D – V G ) characteristics of the programmed states were affected by asymmetry localized in a trapped location along the channel direction. Moreover, the amount of localized trapped charge is strongly affected by drain-source voltage ( V DS ) in the case of HfON TL. HfON TL shows distinguishable separated all programmed states compared to HfO 2 TL. Finally, it was found that all programmed states of HfO 2 and HfON TL show similar characteristics according to the channel length and width ( L / W ) of 2–10/15–90 μ m.