Adsorption of chlorine on TiSi2: Application to etching and deposition of silicide films

The interaction of Cl-2 with polycrystalline TiSi2 has been investigated by temperature programmed desorption to better understand the role of adsorbed chlorine in the etching of TiSi2 films and in the chemical vapor deposition of TiSi2 from TiCl4 and SiH4. Five different desorption states were observed in response to Cl-2 adsorption over a wide exposure range, including the products TiCl4, SiCl4, and SiCl2. The sticking probability for Cl-2 and the desorption kinetics for the products were incorporated into a quantitative model for TiSi2 etching. The predicted etch rates matched closely those measured in an etching reactor operated under typical processing conditions. Etch rates of 200 Angstrom/s were obtained at 600 K with p(Cl2) of 5 x 10(-4) Torr. These rates are an order of magnitude higher than those obtained using plasma-based systems, while the Cl-2 pressure is at least an order of magnitude lower. Coadsorption studies with SiH4 were performed to examine the inhibition effects of surface chlorine during silicide CVD and the role of surface titanium in adsorbate bending.