A MONOS-Type Flash Memory Using a High-k HfAlO Charge Trapping Layer

摘要

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 A1_2O_3, HfO_2, or HfAlO films, instead of Si_3N_4 film. The charge storage and retention characteristics of capacitors with A1_2O_3, HfO_2, or HfAlO as the charge storage layer are compared to conventional MONOS (Si_3N_4 film) capacitors. Mixing 10 atom percent of A1_2O_3 with 90 atom percent 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.