X-Ray reflectivity and spectroscopic ellipsometry as metrology tools for the characterization of interfacial layers in high-κ materials

摘要

In this paper we investigate interface evolution upon annealing in O_2 by means of X-ray reflectivity and spectroscopic ellipsometry on HfO_2 and ZrO_2 thin films deposited with atomic layer deposition (ALD) on Si (100). The analysis of SE data is made with a common optical model adjusting the layer thickness and the surface and interface roughness, while thickness and interface composition are extracted from XRR data by means of the matrix method. The poor electron density contrast between SiOs and Si as opposed to the strong one between HfO_2/ZrO_2 and Si makes the extraction of structural data from XRR data extremely difficult. Information on interdiffusion phenomena occurring between the high-κ layer and the interfacial SiO_2 can be obtained, while SiO_2 growth is hardly detectable.