Atomic Transport and Chemical Stability during Annealing of UltrathinAl2O3Films on Si

Abstract

Ultrathin films of ${\mathrm{Al}}_2{\mathrm{O}}_3$ deposited on Si were submitted to rapid thermal annealing in vacuum or in oxygen atmosphere, in the temperature range from $600$ to $800°\mathrm{C}$. Nuclear reaction profiling with subnanometric depth resolution evidenced mobility of O, Al, and Si species, and angle-resolved x-ray photoelectron spectroscopy revealed the formation of Si-Al-O compounds in near-surface regions, under oxidizing atmosphere at and above $700°\mathrm{C}$. Under vacuum annealing all species remained essentially immobile. A model is presented based on diffusion-reaction equations capable of explaining the mobilities and reproducing the obtained profiles.