Influence of Substrates on Structure Development and Concentration of Residual Impurities in Hafnium–Titanium-Oxide Films Grown by Atomic Layer Deposition

Atomic layer deposition of hafnium–titanium-oxide (HfxTi1–xOy) films on silicon substrates and Ru, RuO2, and Pt seed layers was investigated. The films were grown using HfCl4 and TiCl4 as the metal precursors and H2O and O3 as the oxygen precursors. At a temperature of 350 °C and x ≤ 0.12, tetragonal phases isomorphous with anatase- and rutile-phase TiO2 grew on silicon and on Ru and RuO2, respectively. The films with 0.3 ≤ x ≤ 0.65 grown on silicon and Pt were amorphous, while those deposited on Ru and RuO2 contained the crystal structure isomorphous with orthorhombic HfTiO4. Independently of substrates, the phase isomorphous with monoclinic HfO2 was formed in the films with 0.73 ≤ x ≤ 1.0. The crystal structure influenced the concentration of chlorine impurities that was lower in crystalline films grown on Ru and RuO2 at 350–400 °C than that in amorphous films simultaneously deposited on Si. No significant effect of substrates on the chlorine concentrations was revealed for amorphous films deposited on Si, Ru, and RuO2 at 250 °C. The relative permittivity measured at 10 kHz for HfxTi1–xOy grown on RuO2 ranged from 21 to 90 and monotonically increased with decreasing Hf content.