SUBSTITUTIONAL DIFFUSION OF TRANSITION-METAL IMPURITIES IN SILICON

Near-surface Cu and Ni rich layers are observed by secondary ion mass spectroscopy (SIMS) in intentionally contaminated silicon wafers after thermal oxidation at 950-degrees-C for 35 min. The diffusivities of C u and Ni obtained from their respective SIMS profiles are almost 9 ord ers of magnitude smaller than documented which are widely believed of interstitials, but comparable to that of Group III and V atoms which a re known as substitutional. According to the experimental results, a m odel is proposed for in-diffusion of transition metal atoms contaminat ed on the surface of a silicon wafer during thermal oxidation. In this model, the interstitial and substitutional atoms diffuse independentl y and the slow substitutional diffusion gives rise to a near-surface i mpurity-rich layer.