Effect of annealing in oxygen atmosphere on morphological and electrical properties of iridium and ruthenium thin films prepared by liquid delivery MOCVD

Bottom electrode materials for DRAM capacitors are required to be stable under deposition conditions of high-k materials prepared in an oxidizing ambient at temperatures above 450 °C. It was investigated how annealing of iridium and ruthenium thin films in an oxidizing atmosphere influences their properties.Iridium and ruthenium thin films were deposited using Ir(EtCp)(COD) and Ru(EtCp)2 in toluene solvent by liquid delivery MOCVD. The deposition of thin films via the oxygen-assisted pyrolysis of precursors was carried out on various substrates (SiO2/Si, TiO2/SiO2/Si) at 450 °C. Morphological properties of deposited and annealed thin films were investigated by XRD and FESEM. Electrical resistivity was determined by Van-der-Pauw method.An increase of the annealing temperature from 500 °C to 900 °C results in a change of the phase type, from the metallic phase to the oxide phase. The XRD spectra show the beginning formation of iridium oxide at temperatures above 700 °C. The annealed film resistivity increased by an increase of the annealing temperature. At first, the resistivity increased slightly due to the beginning of the IrO2 and RuO2 formation and, finally, reached the oxide bulk value.