TiSi2 phase transformation characteristics on narrow devices

Accurate prediction of TiSi2 transformation requires test structures with small silicided surface areas. To evaluate the area dependence of the C49 to C54 transformation, a new monitor was developed with minimal silicide surface area. Small area structures were found to exhibit a bimodal resistance distribution that was nearly insensitive to process transformation conditions. Starvation for C54 nucleation sites resulted in a high frequency of non-transformation even at high annealing temperatures. Transmission electron microscopy analysis showed that the Ti silicide in these structures is either C49 or C54 phase, with little or no mixed phases present. A cooperative C54 nucleation mechanism is proposed to explain this phenomena. The presence of small quantities of a molybdenum impurity such as molybdenum during silicide formation has been found to increase the availability of C54 forming nuclei by two orders of magnitude. The molybdenum acts as a catalyst and does not require interface mixing or the creation of an amorphous Si layer to enhance nucleation The addition of molybdenum has been demonstrated to eliminate the bimodal resistance distribution.