Oxygen diffusion in atomic layer deposited ZrO2 and HfO2 thin films on Si (100)

Abstract

In this article, we investigate the oxygen diffusivity in ZrO2 and HfO2 thin films deposited on Silicon (100) by atomic layer deposition. In particular we study the kinetics of the SiO2 interfacial layer growth upon rapid thermal annealing in oxygen atmosphere and the oxygen diffusivity in ZrO2 and HfO2 at high temperature using isotopically enriched O218. The interfacial oxide growth is studied with time-of-flight secondary ion mass spectrometry and transmission electron microscopy. This technique allows us to measure the thickness of the SiO2 layer at the interface between Si and ZrO2 and HfO2 as well as the isotopic composition of oxygen in those films. The oxidation kinetics of silicon in the presence of ZrO2 and HfO2 is found to be totally different than the one occurring on bare silicon annealed in the same condition. During short annealings, a relatively thick SiO2 interfacial layer is formed, independently of O2 partial pressure, suggesting that ZrO2 and HfO2 are injecting oxygen into the silicon. For relatively long annealings Si oxidation is slower than bare silicon oxidation. The annealing in O218 allows us to understand the oxygen exchange mechanisms in ZrO2 and HfO2.