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 HC1/H₂. Coadsorption experiments with TiCl₄ and SiH₄ show that under most conditions H₂ 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 H₂, 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 H₂₎ 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.