Thin CoSi2 formation on SiO2 with low-energy ion irradiation

Cobalt silicides were formed by heat treatment and ion irradiation for stac ked 7 nm Co and 25 nm Si layers on 20 nm SiO2 films. Irradiation was perfor med with 25 keV Ar+ ions to a dose of 5 x 10(15) cm(-2) at sample temperatu res between room temperature and 700 degrees C. The phase, atomic concentra tion profiles, and sheet resistance of the silicide layers were investigate d as a function of the processing temperature. X-ray diffraction measuremen t showed that the phase of CoSi2 was formed by irradiation at temperatures above 300 degrees C, and X-ray photoelectron spectroscopy measurement revea led uniform distributions of Co and Si atoms with the atomic ratio of Co : Si = 1 : 2 for samples irradiated at temperatures above 200 degrees C. Shee t resistance measurement showed that almost complete di-silicidation occurr ed by irradiation at 700 degrees C. It is concluded that the energy deposit ed by ions contributes to the migration of the species for silicidation at a lower temperature, and Co/Si mixed layers with an atomic ratio of 1 : 2 a re easily obtained by irradiation of the stacked thin films with low-energy ions. Since the silicide regions formed in the deposited thin films were d ecomposed during the in irradiation at temperatures below 700 degrees C, th ermal annealing at 700 degrees C is necessary to obtain completely uniform CoSi2 layers after the irradiation.