Investigation of HfO2 and ZrO2 for Resistive Random Access Memory applications

Abstract This work is focused on the investigation of Au/high k/TiN stacks for Resistive Random Access Memories. A screening of high k oxides, commonly used in advanced metal gates, such as HfO 2 and ZrO 2 , is proposed. These oxides were grown on TiN electrodes using Atomic Layer Deposition and Plasma Enhanced Atomic Layer Deposition. The morphological and structural properties of the films were studied as a function of deposition temperature, film thickness and/or annealing using Atomic Force Microscopy, Grazing Incidence X-ray Diffraction and Attenuated Total Reflectance. An amorphous to crystalline transformation was observed with thickness for HfO 2 and ZrO 2 , with deposition temperature for HfO 2 from 300 to 350 °C, and with annealing in N 2 for 1 h at 400 °C for ZrO 2 . According to density measurements obtained using X-ray Reflectometry, HfO 2 and ZrO 2 are suspected to be stoichiometric whatever the thickness. The film stoichiometry was confirmed using X-ray Spectroscopy. Current–voltage measurements were performed on Au/high k/TiN, where Au and TiN are top and bottom electrodes, respectively. Whatever the high k material, the crystallization increases with thickness or/and temperature without any significant modification of the SET operation. The film annealing, which was proposed as an alternative way to crystallize ZrO 2 , may cause a modification of the interfaces, leading to a decrease of the switching performance.