Adsorption of TiCl4 on TiSi2: Application to silicide chemical vapor deposition

The adsorption/desorption kinetics of TiCl4 on polycrystalline TiSi2 have been measured quantitatively by temperature-programmed desorption in order to better understand the chemical vapor deposition of the silicide from TiCl4 and SiH4. For small exposures, only SiCl2 desorbs near 1150 K. The kinetics are second order with respect to surface chlorine, and the desorption activation energy Ed is 85±4 kcal/mol. As this state approaches saturation, SiCl2 desorbs from a second state near 700 K. The kinetics are also second order, but desorption occurs through a continuum of energetic pathways peaking at 57 kcal/mol. As this state saturates, a third desorption peak consisting of SiCl4 appears near 500 K. The kinetics are first order with respect to surface chlorine and also comprise a distribution of energetic pathways, which peak at 33 kcal/mol. Coadsorption studies with SiH4 were also performed. Surface chlorine appears to bond to Si, not Ti, on the surface. These kinetics are utilized to predictively model the chemical vapor deposition of TiSi2 thin films.