Conduction properties of amorphous Ta2O5 films prepared by plasma enhanced chemical vapour deposition

Abstract

Electrical properties of amorphous tantalum oxide, obtained by low pressure (mTorr range) electron cyclotron resonance plasma-enhanced chemical vapour deposition from Ta(OC 2 H 5 ) 5 and O 2 , have been investigated in Al/Ta 2 O 5 /Si structures by current density-voltage and capacitance-voltage measurements. For as-deposited oxide layers, which exhibit high level of leakage currents and interface state densities, the conduction 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 Ta 2 O 5 , the conduction properties are greatly modified and lead to excellent dielectric characteristics in terms of capacitance response and leakage currents (∼10 −10 A cm −2 at 2.5 V).