Study of diffusion and quality control for CoSi_2 formation by oxide-mediated cobalt silicidation with Ti capping

摘要

The mechanism for the enhancement of CoSi_2 thin film formation and film quality control by oxide-mediated cobalt silicidation with a Ti-capping layer is discussed. It is found that Ti absorbs oxygen from the SiO_x layer, which induces weak points in the SiO_x layer and then enhances Co diffusion as well as CoSi_2 formation. The control of the reactions between Ti and SiO_x is significant because a low reaction rate cannot form a suitable thickness of CoSi_2 film, whereas a high reaction rate tends to form the highly resistive CoSi phase. In addition, to maintain the SiO_x layer still existing after annealing is also important because if no SiO_x layer remains, unreacted Co would react with Si directly to form the highly resistive phase of CoSi, leading to the smooth interface between CoSi_2 and Si and dense bulk CoSi_2 thin film being destroyed.