ANALYSIS OF A THIN, SILICON-OXIDE, SILICON-NITRIDE MULTILAYER TARGET BY TIME-OF-FLIGHT MEDIUM-ENERGY BACKSCATTERING

Initial results of a program to optimize the resolution of a time-of-n ight medium energy backscattering system for analyses of thin oxide an d oxynitride films on silicon are reported. Through a redesign of the time-of-flight spectrometer, it has been possible not only to reduce t he timing uncertainty attributable to differing path lengths but also, by deliberately introducing small path length differences correlated with scattering angle, to significantly reduce the kinematic dispersio n resulting from the finite solid angle of the instrument. Straggling and the energy distribution of the secondary electrons which generate the start signal remain as the primary contributors to system timing u ncertainty. Initial measurements of SiO2 and Si3N4 multilayer films in the 10 nm thickness range have been made using channeling in the [110 ] direction of the Si substrate to suppress background. The depth reso lution of the measurements appears to be approximate to 2 nm.