Effect of fluorine incorporation on the thermal stability of PtSi/Si structure

It was observed that the fluorine incorporation from ion implantation improved the high-temperature stability of a PtSi/Si structure. The optimum implantation energy was determined to be the energy at which the maximum percentage of the as-implanted fluorine ion locates at the PtSi/Si interface region. SIMS analysis shows that the fluorine atom piles up at the PtSi/Si interface. XPS analysis indicates that the fluorine atoms at the PtSi/Si interface are bonded to the silicon atoms in a form of SiF₂ or SiF₃. A fluorine-buffer model is proposed to explain the effect of fluorine incorporation. It is postulated that the Si-F layer acts as a buffer layer to change the PtSi/Si interface energy and preserve the integrity of the silicide layer at high temperature. Fluorinated Schottky junctions were fabricated and the electrical characteristics show that the sustainable process temperature can be improved from 650°C for the unfluorinated junctions to higher than 800°C for the fluorinated junctions