Processing and characterization of sol-gel deposited Ta2O5 and TiO2-Ta2O5 dielectric thin films

Abstract

High-dielectric thin films of Ti-doped Ta2O5 were deposited on n+-type silicon substrate using the spin-on sol-gel process. Doping levels of 8 and 46 TiO2 mol% were used. Following deposition, films were processed at temperatures between 600 and 900 °C using rapid thermal annealing in N2O. Spectroscopic ellipsometry (SE) and Rutherford backscattering spectrometry (RBS) were used to determine the thickness and the composition of the thin films and the interfacial reaction layers. Metal insulator-semiconductor capacitor structures were fabricated and impedance-frequency measurements were carried out to measure the dielectric constant of the deposited films. Results from both RBS and SE showed that a SiO2 layer is formed at the Ta2O5/Si interface during processing, but the titanium doping inhibits the kinetics of its formation. We found that the dielectric constant of the highly Ti-doped Ta2O5 film was 78% greater than that of Ta2O5 sol-gel film processed under similar conditions.