Characterization of CoSi₂ 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 mn Co/Si layers on 20 nm 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 nm Co/Si sample irradiated with 40 keV Si²⁺ to 5×10¹⁵ cm^-2, the Fowler-Nordheim tunneling current was observed, and flat-band shift was 1.6 V.