Tunneling spectroscopy of p-type doping in silicon from boron-containing molecular monolayer

•Boron-doping of silicon from molecular monolayer doping•Tunneling spectroscopy analysis of the surface•Surface doping from correlation with numerical simulations

Scanning tunneling spectroscopy was used to investigate surface doping in silicon, based on the grafting of a boron-containing molecular layer and the subsequent thermal diffusion of boron into silicon. Curve fitting of the experimental I(V) characteristics with a planar computation of the tunnel current yields a dopant concentration that is consistent with secondary ion mass spectrometry analyses in the subsurface region. Additional two-point probe electrical measurements performed at variable tip separations indicate a bulk-like transport, that corresponds to a significant diffusion of the boron impurities below the surface of low doped n-type Si wafers. Such results show the interest of multiple-probe scanning tunneling microscopy as a non-invasive technique to determine the electrically active content of doped layers during the fabrication of advanced integrated circuits.

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