HfO_2 Atomic Layer Deposition Using HfCl_4/H_2O: The First Reaction Cycle

摘要

The growth behavior and film quality of HfO_2 deposited by Atomic Layer Deposition (ALD) using HfCl_4/H_2O depends on the hydroxylation of the exposed surface. In this work, we investigate the dependence of the first HfCl_4 chemisorption reaction at 300℃ on the OH density of the silicon surface. We observe that the hydroxyl density, and hence the Hf deposition, on O_3/H_2O 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 since wet oxides are used in CMOS transistors as surface pre-treatment for aggressively scaled HfO_2 gate dielectrics. Moreover, the HfCl_4 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 literature, is applied to gain insight in the stoichiometry of the HfCl_4 chemisorption reaction.