High-fluence Co implantation in Si, SiO₂/Si and Si₃N₄/Si. Part I: Formation of thin silicide surface films

In order to obtain thin CoSi₂ surface layers, Si(1 1 1) and Si(1 0 0), covered by SiO₂ or Si₃N₄ with different thickness, have been implanted by Co to normal fluences from 1×10¹⁶ to 2.6×10¹⁸ ions cm^-2. The Co ions were produced by a high beam current MEtal Vapour Vacuum Arc (MEVVA) ion implantation system with 40 kV acceleration voltage. Time-of-Flight Energy Elastic Recoil Detection (ToF-E ERD) was used to determine the incorporation of Co in the coating materials and silicon substrates. The phase formation and electrical characterization have been studied by X-ray diffraction (XRD) and a four-point probe system. The results reveal that the oxide and nitride layers are uniformly eroded and no significant N or O transport into the bulk Si is observed. After implantation, a thin surface silicide layer (approximately 80 nm) with both a smooth surface topography and sharp interface could be obtained. The optimum Co normal fluence for producing a flat silicide layer depends on the surface film material and its thickness.