Study of electron trapping in the amorphous tantalum oxide thin films prepared by dc magnetron reactive sputtering

Amorphous tantalum pentoxide (Ta2O5) thin films on n-type Si substrates were prepared by d.c, magnetron reactive sputtering deposition technique. It was observed that the leakage current decreased with time when a voltage bias was first applied. The cause of this behavior was investigated using bias-temperature-stress test technique combined with the capacitance-voltage measurement with structures of Al/Ta2O5/Si metal-oxide-semiconductor (MOS) capacitors, and was identified to be owing to electron trapping in the Ta2O5 film and at the Ta2O5/Si interfaces. The current injection technique was further used to correlate the amount of charge trapped in the Ta2O5 with the leakage current passed through the Ta2O5 film, and it was found that most of the trapped electrons were located at the Ta2O5/Si interface. This electron trapping effect on the conduction mechanisms of the Ta2O5 films and the related reliability issues in dynamic random access memories applications are discussed.