Lateral encroachment of Ni-silicides in the source/drain regions on ultrathin silicon-on-insulator

Lateral growth of Ni silicide towards the channel region of metal-oxide-semiconductor transistors (MOSFETs) fabricated on ultrathin silicon-on-insulator (SOI) is characterized using SOI wafers with a 20-nm-thick surface Si layer. With a 10-nm-thick Ni film for silicide formation, p-channel MOSFETs displaying ordinary device characteristics with silicided $p^{+}$ source/drain regions were demonstrated. No lateral growth of ${\mathrm{NiSi}}_x$ under gate isolation spacers was found according to electron microscopy. When the Ni film was 20 nm thick, Schottky contact source/drain MOSFETs showing typical ambipolar characteristics were obtained. A severe lateral encroachment of ${\mathrm{NiSi}}_{\mathrm{x}}$ into the channel region leading to an increased gate leakage was revealed, while no detectable voiding at the silicide front towards the Si channel was observed.