Tantalum oxide films on silicon grown by tantalum evaporation in atomic oxygen

Tantalum pentoxide (Ta2O5) thin layers were grown on Si(100) by evaporation of Ta in an atomic oxygen plasma. The physical and electrical properties of 1000 Angstrom-thick as-deposited films were evaluated. Films grown at 650 degrees C without the presence of the plasma (molecular oxygen) were oxygen-deficient and poorly crystallized, whereas layers grown in the plasma (atomic oxygen) were stoichiometric (within 5%) and crystallized in the beta-Ta2O5 phase. A minimum flux of atomic oxygen during deposition, more than that required for growing films within 5% correct stoichiometry, was crucial for the suppression of the film leakage current. The electrical characterization of amorphous Ta2O5 films grown at 400 degrees C resulted in I-V curves exhibiting an ohmic behaviour at low electric fields, <2 MV cm(-1) (resistivity 10(14) Omega cm), and a leakage current density less than 10(-8) A cm(-2) at 1 MV cm(-1). The measured relative dielectric constant of amorphous Ta2O5 films was 26.