Formation of an interface layer between Al1-xSi xOy thin films and the Si substrate during rapid thermal annealing

Silicon diffusion from the substrate through Al1-xSixOy thin films was investigated by ToF-SIMS depth profiling. Two types of substrate stacks were analyzed: Si wafer with either native oxide or with additional silicon nitride layer. The amount of diffused silicon depends strongly on the type of the substrate. The activation energy for pure alumina was found to be 2.27 ± 0.02 eV and 3.73 ± 0.02 eV for SiO2/Si and Si3N4/SiO2/Si samples, respectively. Furthermore it was proved that the activation energy increases with higher concentration of Si for SiO2/Si samples whereas it decreases for Si3N4/SiO2/Si. Detailed analysis of SIMS depth profiles provide satisfactory explanation of this phenomenon: SiO2 has much stronger tendency to react with Al1-xSixOy material forming an interface layer that restrain further diffusion of Si from the substrate (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)