COMPARISON OF TRANSFORMATION TO LOW-RESISTIVITY PHASE AND AGGLOMERATION OF TISI2 AND COSI2

The phase transformation and stability of TiSi2 on n+ diffusions is investigated. Narrower n+ diffusions require higher anneal temperatures, or longer anneal times, than wider diffusions for complete transitions from the high-resistivity C49 phase to the low-resistivity C54 phase. A model is presented which explains this in terms of the probability of forming C54 nuclei on narrow diffusions and the influence of diffusion width on C54 grain size. The results are that more C49 and C54 nucleation events are required to completely transform narrow lines. For thin TiSi2 (40 nm), there is a narrow process window for achieving complete transformation without causing agglomeration of the TiSi2. The process window decreases with decreasing silicide thickness. A significantly larger process window is achieved with short-time rapid annealing. Similar studies were performed for CoSi2 on n+ and p+ diffusions. No linewidth dependence was observed for the transformation from CoSi(x) to CoSi2. There is a broad process window from 575-degrees-C to 850-degrees-C using furnace annealing, for which the low-resistivity phase is obtained without causing agglomeration.