Influence of oxygen precursors on atomic layer deposition of HfO2 and hafnium-titanium oxide films: Comparison of O3- and H2O-based processes

Abstract Atomic layer deposition (ALD) of HfO2 and hafnium-titanium oxide (HTO) in O3- and H2O-based processes by using a flow-type reactor was studied. Growth per cycle (GPC) recorded for the HfCl4-O3 process at substrate temperatures of 225–600 °C was 0.05–0.13 nm. At temperatures exceeding 300 °C, the O3-based process yielded films with lower GPC and marked thickness gradients, but with lower chlorine contamination levels than the HfCl4-H2O process did. In the HTO films grown from HfCl4, TiCl4 and O3, the thickness gradients decreased with increasing TiO2 content to values that were smaller than those of the films deposited from HfCl4, TiCl4 and H2O. The O3-based ALD of HTO resulted in lower chlorine concentration and higher GPC in the films with Hf/(Hf + Ti) atomic ratios of 0–0.8 and 0.3–0.8, respectively. Independently of the oxygen precursor used, the as-grown HTO films contained anatase at Hf/(Hf + Ti) values of 0–0.16, monoclinic phase with inclusions of cubic, tetragonal or orthorhombic phase at Hf/(Hf + Ti) values of 0.71–1.00, and predominantly amorphous phase at intermediate Hf/(Hf + Ti) values. Differently form the O3-based process, the H2O-based one allowed growth of monoclinic phase with well-developed preferential orientation in the films with Hf/(Hf + Ti) atomic ratios of 0.88–1.00.