ADSORPTION OF TICL4, SIH4, AND HCL ON SI(100) - APPLICATION TO TISI2 CHEMICAL-VAPOR-DEPOSITION AND SI ETCHING

The interactions of TiCl4, SiH4, and HCl with Si(100) have been investigated by temperature programmed desorption (TPD) with the goal of better understanding the initial stages of TiSi2 chemical vapor deposition for circuit metallization and wafer etching with HCl/H-2. Coadsorption experiments with TiCl4 and SiH4 show that under most conditions H-2 and SiCl2 are the main desorption products, with Ti being left behind on the surface. HCl is a minor product. However, at sufficiently low exposures of either TiCl4 or SiH4 the desorption of SiCl2 or H-2, respectively, is inhibited in favor of HCl. A kinetic model involving formation of an HCl complex at defects has been formulated which explains the results quantitatively. HCl adsorption gives rise to the principal desorption products SiCl2 and H-2, with HCl as a minor product. The kinetic behavior can also be explained quantitatively with the proposed model. Implications for TiSi2 growth are discussed with reference to possible growth temperatures and source gas pressures. The mechanism for etching by HCl is further elucidated.