RBS, AES and XPS analysis of ion beam induced nitridation of Si and SiGe alloys

Abstract Nitridation of Si and SiGe alloys under normal incidence 12 keV N + 2 bombardment has been studied by in situ 1 MeV 4 He RBS and by ex situ XPS and AES analysis. The in situ RBS measurements, which alternate with the sputtering/bombardment cycles, show the build-up of the nitrogen content in the silicon and Si .86 Ge .14 sample with increasing N + 2 dose. For the silicon a stoichiometric ratio close to that of Si 3 N 4 is found. In the case of the SiGe alloy a depletion of the Ge from the surface is noticed. Ex situ XPS measurements on the same samples indicate that nitrogen is bonded with silicon and germanium according to the Si 3 N 4 and Ge 3 N 4 phase. AES analysis of the steady state composition gives a depth profile with qualitative information on the chemical binding. Nitridation of a silicon sample with a buried Ge layer demonstrates that during the nitrogen build-up a large densification and even some swelling of the surface layer occurs. The transient region of nitridation before steady state is reached is explained by a two-phase model.