Temperature stability of thin anodic oxide films in metal/insulator/metal structures: A comparison between tantalum and aluminium oxide

The dielectric breakdown of thin (d = 3-4 nm) aluminium and tantalum oxide films was investigated by means of current voltage plots in metal/insulator/metal systems. Dielectric breakdown field strengths, EDB, of 0.6 GV m-1 were found for both oxide types at room temperature. Differences appear in the temperature dependence of EDB. Tantalum oxide films show an unchanged breakdown behaviour for temperatures up to 420 K while aluminium oxide films lose already 80% of their EDB value in the same temperature range. Time-resolved investigations of the electric breakdown revealed intermediate states of both oxide types which were stable for several ms being characterized by an enhanced tunnel current. The breakdown voltage clearly scales with the oxide thickness for both oxide types.