Characteristics of ZrO₂ films with Al and Pt gate electrodes

We investigated interfacial stabilities of ZrO₂ films with Al and Pt electrodes formed by magnetron sputtering upon annealing and consequent changes of their metal-oxide-semiconductor capacitor characteristics. The as-deposited ZrO₂ films deposited using a sputtering power of 300 W were amorphous, while after annealing in N₂ at 600°C for 5 min the films became polycrystalline with a mixture of monoclinic and tetragonal phases. After the deposition of electrodes, we found that the amorphous interlayer which is presumed to be Al₂O₃ was formed at the ZrO₂/Al interface, while platinum (Pt) electrodes showed no interlayer at the interface with ZrO₂ films. The value of the capacitance equivalent thickness for the ZrO₂ film with the Al electrode was larger than that of the case with the Pt electrode by about 12 Å, which is due to the presence of the additional Al₂O₃ interlayer at the Al/ZrO₂ interface. The capacitance-voltage measurement showed that the difference in flatband voltage (V_FB) between the ZrO₂ films and the two different electrodes is about 1.2 V, which is due to the work function difference between the two electrode materials.