Nonvolatile memory characteristics of atomic layer deposited Ru nanocrystals with a SiO2/Al2O3 bilayered tunnel barrier

Abstract

This paper reports a formation process and electrical properties of a nonvolatile memory structure with atomic layer deposited Ru nanocrystals and a SiO2/Al2O3 bilayered tunnel barrier. Al2O3 tunnel barrier/Ru nanocrystals/Al2O3 blocking barrier were deposited sequentially on a SiO2 2 nm/Si substrate by an in situ atomic layer deposition (ALD) process. Ru nanocrystals grown on the Al2O3 surface for 80 ALD cycles had a spatial density of 2.4x10(12) cm(-2) and an average diameter of 2.6 nm (38% standard deviation in the diameter). Charging/discharging behavior of the Ru nanocrystals embedded in the metal-oxide-semiconductor capacitor structure was examined by programming/erase operations and comprehended in terms of asymmetric barrier height of the bilayered tunnel barrier. The memory structure showed charge retention of 91% and 85% after 10(5) s at room temperature and at 85 degrees C, respectively.