In situ formation of Hf-based metal/oxide/nitride/oxide/silicon structure for nonvolatile memory application

Abstract

In this study, we investigated the electrical characteristics of a Hf-based metal/oxide/nitride/oxide/silicon (MONOS) nonvolatile memory (NVM) device formed in situ for the first time. Furthermore, the effects of the in situ HfN gate stack formation process on the electrical characteristics of the Hf-based MONOS device were also investigated by comparing with the device with the Al gate formed ex situ. The drain-current–gate-voltage (ID–VG) characteristics with negligible hysteresis and high yield were realized by using the in situ HfN gate. A memory window (MW) as large as 4.2 V was obtained at the program voltage/time (VPGM/tPGM) of 10 V/1 s and the erase voltage/time (VERS/tERS) of −10 V/1 s. Furthermore, the low-voltage and short-pulse operations, such as ±6 V/2 ms were achieved. Finally, 2-bit/cell operation of the Hf-based MONOS device was demonstrated for the first time utilizing electron injection at the source and drain regions.