CONDUCTION PROPERTIES OF AMORPHOUS TA2O5 FILMS PREPARED BY PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION

Electrical properties of amorphous tantalum oxide, obtained by low pre ssure (mTorr range) electron cyclotron resonance plasma-enhanced chemi cal vapour deposition from Ta(OC2H5)(5) and O-2, have been investigate d in Al/Ta2O5/Si structures by current density-voltage and capacitance -voltage measurements. For as-deposited oxide layers, which exhibit hi gh level of leakage currents and interface state densities, the conduc tion mechanism is clearly attributed to the Poole-Frenkel effect under moderate electric field. After annealing films in a nitrogen ambient below the recrystallisation temperature of Ta2O5, the conduction prope rties are greatly modified and lead to excellent dielectric characteri stics in terms of capacitance response and leakage currents (similar t o 10(-10) A cm(-2) at 2.5 V).