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

High-dielectric thin films of Ti-doped Ta2O5 were deposited on n(+)-type si licon substrate using the spin-on sol-gel process. Doping levels of 8 and 4 6 TiO2 mol% were used. Following deposition, films were processed at temper atures between 600 and 900 degrees 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 ca pacitor structures were fabricated and impedance-frequency measurements wer e carried out to measure the dielectric constant of the deposited films. Re sults from both RES and SE showed that a SiO2 layer is formed at the Ta2O5/ Si interface during processing, but the titanium doping inhibits the kineti cs 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. (C) 1999 Elsevier Science Ltd. All rights reserv ed.