Characterization of CoSi_2 Gate MOS Structure Formed by Ion Irradiation

CoSi2 gate MOS structures were formed by 20, 30, and 40 keV Si2+ Focused Ion Beam (FIB) irradiation to the 14/50 and 21 /75 nm Co/Si layers on 20 mii SiO2 films, and electrical properties of the structures were investigated. The results of the C-V measurement show that the flat-band shift increases with increasing the irradiation damage in SiO2 films. The leak current was also investigated by the I-V measurement, and it is concluded that the leak current was caused by the irradiation damage in SiO2 films and the Si-rich layers near the silicide/SiO2 interface formed by insufficient mixing of Co and Si atoms. In order to optimize the fabrication process of the CoSi2 gate MOS structures by the irradiation, the irradiation damage induced in SiO2 films should be minimized, and the sufficient energy should be deposited in Co/Si layers to induce the mixing of Co and Si atoms. For the 21/75 inn Co/Si sample irradiated with 40 keV Si2+ to 5x 1015 cm-2, the Fowler-Nordheirn tunneling current was observed, and flat-band shift was 1.6 V.