Current conduction mechanism in TiO2 gate dielectrics

Electrical properties of titanium oxide (TiO2) deposited on strained-Si heterolayers by plasma enhanced chemical vapor deposition (PECVD) from an organo-metallic precursor titanium isopropoxide (TTIP), have been investigated in Al/TiO2/strained-Si structures by capacitance-voltage (C-V) and current-voltage (I-V) measurements. For as-deposited layers, which exhibit high level of interface states and leakage current, both Poole-Frenkel (PF) and Schottky emission (SE) effects govern the conduction mechanism. After post deposition annealing in pure nitrogen ambient at 400 °C, the conduction mechanism changes and the interface state density reduces by an order of magnitude. It is found that after annealing, only Schottky emission dominates the conduction mechanism at a low electric field.