Influence of annealing condition on the properties of sputtered hafnium oxide

Abstract

Hafnium oxide thin films were deposited on p-type (100) silicon wafers by reactive dc magnetron sputtering. Prior to the deposition of HfO2 films, a thin Hf film was deposited. Sputtered HfO2 thin films deposited at room temperature remain amorphous at T<650°C and orthorhombic phases were observed above 650 °C. The monoclinic phase which is a stable HfO2 polymorphic form appeared after annealing above 800 °C. Capacitance equivalent thickness values decreased and leakage characteristics are improved by the Hf interlayer and O2 settlement process. The decrease of accumulation capacitance values upon annealing is due to the growth of an interfacial layer upon post-annealing. The flat band voltage (VFB) shifts negatively due to positive charge generated during post-annealing.