Formation of High Quality Tantalum Oxide Thin Films at 400°C by 172 nm Radiation

Thin uniform tantalum oxide films on Si were formed at 400°C using photo-assisted sol-gel process from a Xe₂^* excimer lamp. Carbon contamination levels as low as 2.0 at% were obtained which compare favourably with the levels found (4–7%) by alternative techniques. Ellipsometry, electron probe X-ray microanalysis, capacitance-voltage, and current-voltage measurements were employed to characterise the films whose overall properties are found to be superior to those for Chemical Vapor Deposition (CVD) deposited films. Leakage current densities as low as 9.0×10^-8 A·cm^-2 at 0.5 MV/cm are obtained for the as-prepared films, several orders of magnitude lower than for any other as-grown films prepared by any other technique. A subsequent low temperature (400°C) annealing improves this to 2.0×10^-9 A·cm^-2 at 0.5 MV/cm. These values are essentially identical to those only previously formed for films annealed at temperatures between 600 and 1000°C.