THE EFFECTS OF SUBSTRATE AND ANNEALING AMBIENT ON THE ELECTRICAL-PROPERTIES OF TA2O5 THIN-FILMS PREPARED BY PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION

Ta2O5 thin films were deposited onto p-Si, n(+)-Si, RTN (rapid thermal nitridation) nitride and HSG (hemispherical grain) Si substrates by plasma enhanced chemical vapor deposition (PECVD). The physical and electrical properties were characterized after annealing in the temperature range 600-900 degrees C in N-2 or O-2 ambient. Fourier transform IR analysis revealed that an interfacial oxide which affected the electrical properties of Ta2O5 thin film was formed at the Ta2O5-Si interface during annealing above 800 degrees C. The electrical properties of the Ta2O5 thin film were strongly dependent on annealing conditions. The Ta2O5 thin films showed 1.5 times higher capacitance, but higher leakage current owing to the edge effect, on the enlarged surface area of HSG Si than on the flat p-Si or n(+)-poly Si. RTN treatment of Ta2O5 thin films on the Si substrate reduced the leakage current without loss of the high dielectric constant.