THE DETERMINATION OF SURFACE CONTAMINATION ON SILICON BY LARGE ANGLE ION SCATTERING

Experiments are described in which the energy spectra of 1-MeV He+ ions backscattered 150° from a silicon surface have been used to identify and measure the contamination on the surface. Contamination from hydrofluoric acid solutions containing gold and copper in concentrations ranging from 0.1 to 100 parts per million was studied. Less than one half a monolayer of contaminant was easily resolved and identified. Coverages of this order were obtained from solutions containing 0.1 ppm of the contaminant.