A MONOS-type flash memory using a high-k HfAlO charge trapping layer

Abstract

Metal-oxide-nitride-oxide-silicon (MONOS) type memory devices with TaN/HfN gate and a high dielectric constant (high-k) charge trapping layer were experimentally realized by employing a SiO 2/high-k/SiO 2 structure that used Al 2O 3, HfO 2, or HfAlO films, instead of Si 3N 4 film. The charge storage and retention characteristics of capacitors with Al 2O 3, HfO 2, or HfAlO as the charge storage layer are compared to conventional MONOS (Si 3N 4 film) capacitors. Mixing 10 atom % of Al 2O 3 with 90 atom % of HfO 2 to form HfAlO improves the charge retention capability of HfO 2 without severely degrading its programming speed. Unlike conventional MONOS memory devices, HfAlO devices also exhibit better resistance to over-erase. The differences in the program/erase characteristics and the charge storage capability between the different structures are discussed. © 2004 The Electrochemical Society. All rights reserved.