HIGH-RESISTIVITY CO AND TI SILICIDE FORMATION ON SILICON-ON-INSULATORSUBSTRATES

Under the condition of excess metal deposition, the formation of Co an d Ti silicides on (001) silicon-on-insulator (SOI) substrates was inve stigated. In the Co silicide case, a high-resistivity Co silicide film was formed after a high temperature anneal (1000 degrees C for 30 s). Transmission electron microscopy (TEM) revealed that the phase formed was CoSi. The phenomenon of CoSi being the most stable phase, instead of CoSi2, at high temperatures can be understood from both kinetics a nd thermodynamics. In the Ti silicide case, the most dominant phase wa s C49-TiSi2, therefore the film resistance was high even after high te mperature annealing (900 degrees C for 20 s). The film morphology was thermally stable on further annealing and the resistance decreased gra dually by means of partial transformation of C49-TiSi2 to the C54-TiSi 2 phase. For device applications, high resistance silicide films are n ot desirable, therefore the metal thickness and consequent silicide th ickness have to be controlled precisely.