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

Atomic layer deposition (ALD) of HfO2 and hafnium-titanium oxide (HTO) in O-3- and H2O-based processes by using a flow-type reactor was studied. Growth per cycle (GPC) recorded for the HfCl4-O-3 process at substrate temperatures of 225-600 degrees C was 0.05-0.13 nm. At temperatures exceeding 300 degrees C, the O-3-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 O-3, 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 O-3-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 O-3-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.