Defect state D (0.8eV) was experimentally detected in Ta2O5 capacitors with ultra-thin (<10nm) films by using zero-bias thermally stimulated current spectroscopy correlated with leakage current. The defect state D could be more efficiently suppressed by using N2O rapid thermal annealing instead of using O2 rapid thermal annealing for post-deposition annealing and by using TiN instead of Al for the top electrode. It was proposed that defect D was probably the first ionization level of the O vacancy deep double donor. Other important defects were Si/O-vacancy complex single donors and C/O-vacancy complex single donors.

Detection of Oxygen Vacancy Defect States in Capacitors with Ultra-Thin Ta2O5 Films by Zero-Bias Thermally Stimulated Current Spectroscopy. W.S.Lau, L.L.Leong, T.Han, N.P.Sandler: Applied Physics Letters, 2003, 83[14], 2835-7