Leakage currents in Ti−O/Ta2O5 thin film deposited on Ta/Ti/Al2O3

The electrical characteristics of Ta/Ta2O5 films and Ta/Ti−O/Ta2O5 films deposited by RF reactive sputtering on Ta/Ti/Al2O3 substrates were investigated. Ta was used for the bottom and upper electrodes in order to simplify the fabrication process. Dielectric materials were annealed at 700°C for 60 sec under vacuum. XRD analysis showed that Ta was crystalline and Ta2O5 was amorphous in an as-deposited state, but amorphous Ta2O5 was transformed to a crystalline state by rapid thermal heat treatment. We compared lnJ-E2, C−V, and C−F of both as-deposited and annealed dielectric thin films deposited on the Ta bottom electrode. From these results, we concluded that introducing a Ti−O buffer layer could reduce the leakage current. The conduction mechanisms of Ti−O/Ta2O5 could be interpreted appropriately by hopping conduction and space-charge-limited current.