REACTION OF TI WITH WSI2

Reactions between Ti and WSi2 have been studied between 400 and 800 de grees C. Reactions at the Ti-WSi2 interface begin at 600 degrees C, wi th the formation of TiSi. The TiSi is converted to TiSi2 at 800 degree s C. The formation temperatures for TiSi and TiSi2 are higher than tho se observed for Ti on Si, presumably because the Si supply is limited by relatively slow diffusion of Si through WSi2. At 700 degrees C, loc alized formation of Ti silicide is also observed below the WSi2, due t o Ti diffusion through grain boundaries in the WSi2. These results sug gest that post-metallization anneals of Ti on WSi2 polycide structures should be kept below 700 degrees C to avoid device degradation. (C) 1 997 American Institute of Physics.