In-situ RBS for oxygen ion implantation systems

In-situ measurement of backscattered oxygen ions has been studied with the goal of providing real-time in-situ diagnostics of contamination levels during ion implantation. Heavy metal contamination caused by ion beam sputtering of beam defining apertures and beam line construction components is a significant concern for producing high quality SIMOX wafers. If present during implantation, these contaminants will concentrate near the implanted surface with decreasing concentrations down to the end-of-range of the implanted ions, Ultimately, these heavy metals will diffuse to the SOI interfaces and possibly degrade device performance. A 5 mm diameter (2 to 200 /spl mu/A) 65 KeV beam of oxygen ions, used to probe various elemental target materials, produced distinctive edges in the backscattered ion energy spectrum that was measured using an electrostatic analyzer and channeltron detector. Additional samples with thin metal films deposited on silicon substrates were measured showing excellent agreement between theoretical and measured spectra for both thickness and concentration. In this paper we present a description of the experimental apparatus along with the data and analysis. We also discuss the future implementation plans for an in-situ monitor for use in SIMOX implantation.