HfO2 Atomic Layer Deposition Using HfCl4/H2O: The First Reaction Cycle.

The growth behavior and film quality of HfO₂ deposited by atomic layer deposition (ALD) using HfCl₄/H₂O depends on the hydroxylation of the exposed surface. In this work, we investigate the dependence of the first HfCl₄ chemisorption reaction at 300°C on the OH density of the silicon surface. We observe that the hydroxyl density, and hence the Hf deposition, on O₃/H₂O wet oxides depends on the initial preparation as well as on the stabilization time in the ALD reactor. A good understanding of the initial nucleation behavior is necessary because wet oxides are used in complementary metal-oxide-semiconductor transistors as surface pretreatment for aggressively scaled HfO₂ gate dielectrics. Moreover, the HfCl₄ chemisorption reaction is used to estimate the hydroxylated fraction of these surfaces by means of theoretical models. Finally, the temperature dependence of the OH density, as available in the literature, is applied to gain insight into the stoichiometry of the HfCl₄ chemisorption reaction. [ABSTRACT FROM AUTHOR]