A study was made of the leakage current mechanism in Ru-gated MOS capacitors with ultra-thin HfxSi1−xOy gate dielectrics, grown by atomic phase deposition. The dielectrics were subjected to rapid thermal annealing in an O atmosphere at 700 to 1000C. Temperature-dependent current-voltage characteristics exhibited trap-assisted tunneling through the Hf-silicate film annealed at 700C. The energy trap level was 2eV below the dielectric conduction band edge. On the other hand, direct tunneling was found to control the leakage current through gate dielectrics annealed at 800 and 900C. Based on a microstructural study, the trap level was attributed to hafnia O vacancies in the Hf-silicate.

Evidence of Hafnia Oxygen Vacancy Defects in MOCVD Grown HfxSi1−xOy Ultrathin Gate Dielectrics Gated with Ru Electrode. M.Ťapajna, A.Rosová, K.Hušeková, F.Roozeboom, E.Dobročka, K.Fröhlich: Microelectronic Engineering, 2007, 84[9-10], 2366-9