Property and microstructure evaluation of Pd-inserted nickel monosilicides

A composition consisting of 10 nm-Ni/1 nm-Pd/(30 nm or 70 nm-poly)Si was thermally annealed using rapid thermal for 40 seconds at 300-1100°C to improve the thermal stability of conventional nickel monosilicide. The annealed bilayer structure developed into Ni(Pd)Si_x, and the resulting changes in sheet resistance, microstructure, phase, chemical composition, and surface roughness were investigated. The suicide, which formed on single crystal silicon, could defer the transformation of NiSi₂, and was stable at temperatures up to HOO0C. It remained unchanged on polysilicon substrate compared with the sheet resistance of conventional nickel suicide. The suicides annealed at 700°C, formed on single crystal silicon and 30 nm polysilicon substrates exhibited 30 nm-thick uniform suicide layers. However, suicide annealed at 1,000°C showed preferred and agglomerated phase. The high resistance was due to the agglomerated and mixed microstructures. Through Xray diffraction analysis, the suicide formed on single crystal silicon and 30 nm polysilicon substrate, showed NiSi phase on the entire temperature range and mixed phases of NiSi and NiSi₂ on 70 nm polysilicon substrate. Through scanning probe microscope (SPM) analysis, we confirmed that the surface roughness increased abruptly until 36 nm on 30 nm polysilicon substrate while not changed on single crystal and 70 nm polysilicon substrates. The Pd-inserted nickel monosilicide could maintain low resistance in a wide temperature range and is considered suitable for nano-thick suicide processing.