CONDUCTION MECHANISMS IN AMORPHOUS AND CRYSTALLINE TA2O5 THIN-FILMS

Electrical properties and leakage current mechanisms of amorphous and polycrystalline tantalum pentoxide (Ta2O5) films were studied. Ta2O5 t hin films were deposited on Pt/SiO2/n-Si substrate by reactive magnetr on sputtering and then annealed at temperatures ranging from 500 to 80 0 degrees C for 30 min in O-2. The as-deposited films were amorphous a nd showed good electrical properties in terms of a dielectric constant of about 31 and leakage current density of 10(-10) A/cm(2) at 100 kV/ cm. The leakage current flowing through Ta2O5 film increases from 10(- 10) to 10(-7) A/cm(2) following the annealing. The conduction mechanis m at low electric fields (100 kV/cm) is due to Ohmic conduction. On th e other hand Schottky mechanism dominates at the intermediate fields ( 100-350 kV/cm) and Poole-Frenkel becomes predominant at high fields (> 350 kV/cm). The increase in leakage current density in the crystallize d film is due to Si penetrated into the Ta2O5 grain and grain boundary from the underlying SiO2/n-Si substrate. (C) 1998 American Institute of Physics.