Processing and characterisation of sol–gel deposited Ta 2O 5 and TiO 2–Ta 2O 5 dielectric thin films

Abstract

High-dielectric thin films of Ti-doped Ta 2O 5 were deposited on n +-type silicon substrate using the spin-on sol–gel process. Doping levels of 8 and 46 TiO 2 mol% were used. Following deposition, films were processed at temperatures between 600 and 900°C using rapid thermal annealing in N 2O. 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 SiO 2 layer is formed at the Ta 2O 5/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 Ta 2O 5 film was 78% greater than that of Ta 2O 5 sol–gel film processed under similar conditions.