Electrical characterisation and reliability of HfO2 and Al2O3–HfO2 MIM capacitors

Current leakage and breakdown of MIM capacitors using HfO₂ and Al₂O₃–HfO₂ stacked layers were studied. Conduction in devices based upon HfO₂ layers thinner than 8 nm is probably dominated by tunnelling. Al₂O₃–HfO₂ stacked layers provide a limited benefit only in term of breakdown field. Constant-voltage wear-out of samples using insulating layer thicker than 6 nm is dominated by a very fast increase of the leakage current. A two step mechanism involving the generation of a conduction path followed by a destructive thermal effect is proposed to explain breakdown mechanism.