Effect of BF2 + implantation on void formation in Ti-salicided narrow polysilicon lines

Abstract

We report the formation of voids in TiSi2 films formed on deep submicron BF2(+)-implanted polysilicon (polySi) lines. The void formation was strongly dependent on BF2(+)-implant dose, the p+ annealing temperature, and the polySi linewidth. Using plan-view scanning electron microscopy and cross-sectional transmission electron microscopy, both surface and subsurface voids were observed. The voids were distributed predominantly along the center of the p+ polySi lines and near the TiSi2/polySi interface, especially for linewidths less than subquarter-micrometer. X-ray photoemission spectroscopic analysis detected a mixture of SiFx (1 ≤ x ≤ 4) and TiFx (x = 3, 4) like species near the TiSi2/polySi interface during an in situ annealing of Ti and Si, providing further evidence that the voids are fluorine-assisted species.