The mechanism for the enhancement of CoSi2 thin film formation and film quality control by oxide-mediated cobalt silicidation with a Ti-capping layer was considered. It was found that Ti absorbed O from the SiOx layer, which introduced weak points into the SiOx layer and then enhanced Co diffusion as well as CoSi2 formation. The control of the reactions between Ti and SiOx was significant because a low reaction rate could not form a suitable thickness of CoSi2 film, whereas a high reaction rate tended to form the highly resistive CoSi phase. Maintaining the SiOx layer still existing after annealing was also important because, if no SiOx layer remained, unreacted Co would react with Si directly to form the highly resistive phase of CoSi, leading to the smooth interface between CoSi2 and Si and dense bulk CoSi2 thin film being destroyed.

Study of Diffusion and Quality Control for CoSi2 Formation by Oxide-Mediated Cobalt Silicidation with Ti Capping. J.J.Chang, C.P.Liu, T.E.Hsieh, Y.L.Wang: Journal of Vacuum Science & Technology B, 2005, 23[5], 1952-5