Electrical conduction mechanism in high-dielectric-constant ZrO2 thin films

The electrical conduction mechanism in zirconium oxide (ZrO2) thin films as a function of temperature T and electric field E was studied. Al/ZrO2/p-Si metal-insulator-semiconductor (MIS) capacitors were fabricated. With the Al electrode biased negative, the conduction mechanism in the electrical field of 0.81 MV/cm < E < 1.40 MV/cm and in the temperature range of 375 K < T < 450 K is found to be modified Schottky emission. The intrinsic barrier height between Al and ZrO2 is 1.06 eV. At higher electrical fields of 1.50 MV/cm < E < 2.25 MV/cm and higher temperatures of 375 K < T < 450 K, the electrical conduction is dominated by modified Poole-Frenkel emission. The extracted trap barrier is 0.83 eV. With the Al electrode biased positive, the conduction mechanism is found to be Schottky emission at the electrical field 0.20 MV/cm < E < 0.60 MV/cm and higher temperature range of 425 K < T< 450 K. The barrier height between Si and ZrO2 is 1.0 eV. Based on these results, an energy band diagram of the Al/ZrO2/p-Si system is proposed.