Effects of oxidant selection for atomic layer deposition on impurity removal and crystallinity of as-grown Hf1− x Zr x O2 thin films

10 nm-thick Hf1−xZrxO2 (HZO) films were deposited on TiN by atomic layer deposition at 250 °C using H2O2 or H2O as an oxidant with various exposure time. X-ray diffraction results showed that all as-grown films exhibited an overlapping peak associated with the orthorhombic (O)/tetragonal (T)/cubic (C) phases, while no notable peaks of the monoclinic phase were observed. With extending oxidant exposure time, both H2O2- and H2O-based films exhibited enhanced O/T/C phases peak area and reached saturation under sufficient oxidation. In the saturated region, the O/T/C phases peak area of H2O2-based films was ∼30% higher than that of H2O-based films. Carbon and nitrogen impurities were considered to remain in the films as residual precursor-ligand fragments due to incomplete reaction. With evaluation of impurity levels, both H2O2- and H2O-based HZO films exhibited a trend that crystallinity increases as impurity concentration of carbon and nitrogen decreases. Moreover, H2O2-based films had carbon and nitrogen concentrations approximately one order of magnitude lower than those of H2O-based films. These results suggest that impurity removal during the oxidation step is a critical factor for enhancing the crystallization of as-grown HZO films.