Reactively sputtered hafnium oxide on silicon dioxide: Structural and electrical properties

• The electrical and structural properties of HfO2 grown on SiO2 are investigated.
• Amorphous and polycrystalline HfO2 is observed in as-grown layers with >21 nm.
• Conductance peaks appear in samples with HfO2 thicker than 90 nm.
• Defects at the interface or in near-interface oxide lead to the shift of Ufb.
• The observed defects are stable even after the heat treatment at 950 °C.

The structural and electrical properties of SiO2/HfO2 with different thickness of HfO2 grown by the magnetron sputtering technique are investigated. We show that a part of HfO2 is always amorphous in as-grown layers whereas the polycrystalline phase in the form of conical grains can be also observed in HfO2 with the thickness more than 21 nm. The presence of the conical grains seems to be responsible for the formation of interface states or near-interface oxide defects which influence the electrical properties of the films leading to the shift of the flat-band voltage and to the appearance of the conductance peaks near 0 V. These defects are found to be stable even after the heat treatment at about 950 °C which leads to the crystallization of HfO2 films irrespective of their thickness.