Abstract
The effects of stress on the formation of nickel silicides on SOI (silicon-on-insulator) wafers have been investigated by sheet resistance measurements, glancing-angle x-ray diffraction analysis and transmission electron microscopy. Tensile stress was induced by the difference of thermal expansion coefficients of Si and SiO2. The thinner the top silicon layer, the higher tensile stress was induced. For nickel on blank and SOI substrates after rapid thermal annealing (RTA) at 400℃ for 30 sec, the thickness of NiSi film was found to increase with the tensile stress. In the mean time, the thickness of Ni2Si became thinner and discontinuous. The effects of stress on the formation of NiSi to NiSi2 thin film have also been investigated. Tensile stress present in the silicon substrate was found to promote the formation of epitaxial NiSi2. In addition, tensile stress was found to favor the growth of polycrystalline NiSi2 over epitaxial NiSi2. The results indicated that the tensile stress promotes the Ni diffusion to facilitate the formation of NiSi2.