Suppressing boron penetration and cobalt silicide agglomeration in deep submicron p-channel metal–oxide–semiconductor devices

Abstract

Two discrete processing techniques have been combined for the doping and silicidation of thin (∼125 nm) amorphous silicon (a-Si) film. One technique uses an implantation barrier consisting of a stack of low temperature cobalt silicide (CoSi) and a-Si. The other technique incorporates nitrogen (N2+) to suppress CoSi2 agglomeration. When combined, the implantation barriers consisting of the CoSi/a-Si stack or a-Si films reduce boron penetration in p-channel metal–oxide–semiconductor devices and the implanted N2+ hinders cobalt silicide agglomeration. The two processing approaches presented here differ only in the implantation sequence. TRIM (transport of ions in matter) simulation has been used to predetermine the approximate doses and energies of implantation species. Sheet resistances are measured to assess the silicide thickness and quality of the resulting films. Depth profiles for boron, nitrogen, fluorine and cobalt have been extracted analytically by secondary ion mass spectroscopy. Transmission electron microscopy micrographs have been included to show the silicide/Si interface and also to manifest that there is no grain boundary grooving in the resulting cobalt silicide film.