DOPANT REDISTRIBUTION DURING THE FORMATION OF IRON SILICIDES

Iron disilicide (beta-FeSi2) is a semiconducting silicide with a direc t bandgap of about 0.87 eV, thus rendering it attractive properties fo r opto-electronic applications. The compatibility with standard IC-tec hnology is of great importance for future on-chip optical interconnect s. This study is focused on the dopant behaviour during processing of iron silicides. The redistribution of dopants during silicide formatio n was studied utilising SIMS analysis. Different silicide procedures w ere investigated. The silicides were either formed by reacting a depos ited iron film with crystalline silicon or from a bilayer structure co nsisting of excess silicon on top of the iron film. Cross-sectional TE M micrographs of the bilayer structures showed an epitaxial regrowth o f the excess silicon at the crystalline silicon-silicide interface whe n the system was fully reacted. Arsenic implanted silicon was observed to yield good epitaxial regrowth while boron showed an inferior cryst alline regrowth. The dopant redistribution was found to depend on the formation condition. Boron and phosphorus were depleted at the silicid e-silicon interface, while arsenic was found to yield a small accumula tion at the interface.