Thin Films of CoSi2 Co-Deposited onto Si1-xGexAlloys

Abstract

AbstractCobalt disilicide films have been formed on strained epitaxial Si0.80Ge0.20/Si(100) alloys via co-deposition of silicon and cobalt. Co-deposition is shown to improve the epitaxy and prevent the phase segregation commonly observed with the formation of Co/SiGe contacts using other methods such as the direct deposition of cobalt onto SiGe or the sequential deposition of a silicon sacrificial layer and cobalt onto SiGe. EXAFS measurements at the cobalt K edge indicate that co-deposited films annealed at 500–700° C are indeed crystalline CoSi2 throughout this temperature range. The XRD patterns of the co-deposited films do not exhibit any of the CoSi2 (111), (220) or (311) peaks normally associated with other preparation methods. The sheet resistance and r.m.s. roughness of the CoSi2 films increase monotonically with annealing temperature. These results indicate that co-deposited films are epitaxial to the (100)-oriented SiGe substrate and suggest that low thermal budget, low resistivity contacts to strained SiGe can be grown with this method. Issues related to the presence of Ge at the CoSi2/substrate interface will be discussed.