EFFECT OF ION-BEAM MIXING TEMPERATURE ON COBALT SILICIDE FORMATION

In this study, the influence of ion-beam mixing temperature on CoSi2 f ormation during subsequent annealing was investigated. For mixing of c obalt layers on silicon, germanium ions were implanted at various subs trate temperatures ranging from 25 to 500-degrees-C. RBS and TEM inves tigations showed that only in the case of mixing temperatures at or ab ove 400-degrees-C, silicide phases like Co2Si, CoSi, and CoSi2 were fo rmed during mixing. Annealing at 700-degrees-C resulted in a complete conversion into CoSi2 for samples mixed at 400 and 500-degrees-C where as no reaction could be observed for all other samples. A second annea ling step at 1000-degrees-C was necessary to achieve complete silicida tion also for these samples. However, only ion-beam mixing at 400 and 500-degrees-C led to uniform CoSi2 layers with abrupt silicide-silicon interfaces. It can be concluded that radiation enhanced reaction take s place when performing ion-beam mixing above a critical temperature. In this case, a sufficient metal amount could be mixed into the silico n surface resulting in uniform silicide growth.