Thermal stability of HfO2-on-GaAs nanopatterns

Abstract

We have evaluated the effect of thermal annealing on the morphology, crystalline phase and elemental composition of high-k dielectric HfO₂-on-GaAs nanopatterns at 500–620 °C by using atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS). While the HfO₂–GaAs interface continues to be atomically abrupt at 620 °C, we have found a gradual shrinkage in the pattern linewidth and period with increasing temperature. Facet formation triggered by a nanoscale-modulated sequence of tensile and compressive stresses on the GaAs substrate, observed at 620 °C, has been attributed to a volumetric expansion of the HfO₂ nanostructures, caused by the tetragonal/cubic to monoclinic HfO₂ phase transformation and, to a lesser extent, by solid-state diffusion of As into HfO₂.