Characterization of atomic layer deposition using X-ray reflectometry

Abstract

This work addresses current limitations of X-ray reflectometry (XRR) for modeling thin films and provides a basis for their improvement. Better accuracy in the characterization of novel thin film structures requires better model selection techniques and better knowledge of the theoretical limitations of current XRR analysis techniques. We use hafnium dioxide (HfO2) nanoscale (≈ 1 nm) thin films deposited by atomic layer deposition (ALD) to study the limitations of current techniques. These structures are of strategic importance as CMOS gate and barrier materials. We show that XRR modeling - for our measured data range and counting statistics - will fail for thicknesses less than 1 nm. We also show that a two-layer model (HfO2/SiO xHfy/Si substrate) is more plausible than a one-layer model (HfO2/Si substrate) for the measured data. © 2005 American Institute of Physics.