Reaction of Ti with WSi2

Reactions between Ti and WSi2 have been studied between 400 and 800 degrees C. Reactions at the Ti-WSi2 interface begin at 600 degrees C, with the formation of TiSi. The TiSi is converted to TiSi2 at 800 degrees C. The formation temperatures for TiSi and TiSi2 are higher than those observed for Ti on Si, presumably because the Si supply is limited by relatively slow diffusion of Si through WSi2. At 700 degrees C, localized formation of Ti silicide is also observed below the WSi2, due to Ti diffusion through grain boundaries in the WSi2. These results suggest that post-metallization anneals of Ti on WSi2 polycide structures should be kept below 700 degrees C to avoid device degradation. (C) 1997 American Institute of Physics.