Characterization of ultrathin dopant segregation layers in nanoscale metal–oxide–semiconductor field effect transistors using scanning transmission electron microscopy

Abstract

Silicide/Si source/drain interfaces (Co–silicide and Ti–silicide) in nanoscale metal–oxide–semiconductor field effect transistors (MOSFETs) were investigated using scanning transmission electron microscopy and electron energy loss spectroscopy. Z-contrast images of the N-type doped device show substitutional arsenic segregation on Si lattice sites with a very narrow profile precisely at the Co–silicide/Si interfaces. A detailed comparative electron energy loss study of As-doped and undoped devices reveals that arsenic remains electrically active and supplies additional charge carriers at the interface. These characteristics are desirable for optimum device performance with minimum contact resistance. A similar effect is also observed in MOSFETs with a Ti-silicided source/drain.