Recovery of the Si–SiO2 interface studied by self-diffusion after high fluence ion implantation of 28Si

Abstract

In this work, we discuss the recovery of the Si–SiO2 interface after high fluence ion implantation of isotope pure 28Si fluences of 1×1016–5×1016at./cm2 into 50nm thick thermally grown SiO2 on (100)-silicon and subsequent thermal treatment. The implantation energy was chosen to be 32keV in order to place the maximum of the implanted concentration profile into the interface. The ion implanted Si provokes ion induced atomic mixing and over-stoichiometric 28Si in the SiO2 layer.The depth profiles of 28Si, 29Si and 30Si isotopes, the trimer 28Si3 and oxygen were measured by dynamic secondary ion mass spectrometry (SIMS) using low energy Cs+ sputter ions with 1.5keV before and after annealing of the samples. Matrix effects, often encountered in dynamic SIMS depth profiling, obscuring the measured secondary ion yield depth profiles in close vicinity to the SiO2–Si interface, were eliminated by analyzing the Si isotope composition. By this technique material transport processes involved in the recovery of the interface by self-diffusion was studies. It was found, that transport of oxygen dominates and leads to oxidation of excess Si in close proximity to the interface.