A study was made of the leakage current mechanism in Ru-gated MOS capacitors with ultra-thin HfxSi1−xOy gate dielectrics grown by atomic vapour deposition. The dielectrics were annealed by rapid thermal annealing in O atmosphere at 700 to 1000C. Temperature dependent current-voltage characteristics exhibited trap-assisted tunnelling 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 tunnelling 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