Formation of high-temperature stable Co-silicide from Co_0.92Ta_0.08/Si systems

We investigated the formation and thermal stability of Co-silicide films using Co-Ta alloy films on (100) Si substrates. Co-Ta alloy films were deposited by direct current (DC) magnetron sputtering using Co and Ta targets. The content of Ta in the films was controlled at 8 at.%. The Co-silicide films were formed through a rapid thermal annealing (RTA) process in N₂ ambient. Compared with the Co/Si systems, the formation of CoSi₂ occurs at higher temperatures in Co_0.92Ta_0.08/Si systems. X-Ray diffractometry (XRD) analyses showed the presence of strong (200)-preferred orientation in the Co-silicide films formed from Co_0.92Ta_0.08/Si systems. We observed that Co-silicide films formed from Co_0.92Ta_0.08/Si systems maintained low sheet resistance values upon annealing at 950°C, while those of Co-silicide from Co/Si systems increased significantly. The improvement of the thermal stability of the Co-silicide films from Co_0.92Ta_0.08/Si systems is due to the formation of Ta-compounds such as the TaSi₂ phase at the grain boundaries or at the surface of the CoSi₂ films.