Adsorption and desorption kinetics for SiH₂Cl₂ on Si(111) 7×7

The adsorption and desorption kinetics for dichlorosilane (SiH₂Cl₂) on Si(111) 7×7 were studied using laser‐induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. The TPD experiments monitored H₂, HCl, and SiCl₂ desorption products at 810, 850, and 1000 K, respectively. H₂, HCl, and SiCl₂ desorption products were also observed in the LITD yield at all surface coverages. In agreement with the TPD studies, linear ramp LITD experiments monitored the disappearance of the H₂, HCl, and SiCl₂ LITD signals at 810, 850, and 1000 K. LITD measurements determined the initial reactive sticking coefficient (S₀) of SiH₂Cl₂ on Si(111) 7×7 versus surface temperature. The sticking coefficient was S₀≊0.36 at temperatures from 150 to 200 K. Above 200 K, the sticking coefficient decreased to S₀≊0.10 at 350 K and S₀≊0.0025 at 850 K. The temperature‐dependent sticking coefficient was consistent with a precursor‐mediated adsorption model. As a function of surface coverage following SiH₂Cl₂ exposure, TPD studies observed that the HCl desorption yield decreased relative to the H₂ and SiCl₂ desorption yields. These results indicated that when more hydrogen desorbs as H₂ at higher coverages, the remaining chlorine is forced to desorb as SiCl₂. TPD experiments also determined that the surface chlorine coverage saturated and was independent of surface temperature after large SiH₂Cl₂ exposures on Si(111) 7×7. Epitaxial growth of silicon by dichlorosilane chemical vapor deposition can be predicted using the measured adsorption and desorption kinetics for dichlorosilane on Si(111) 7×7. When these kinetics are employed together with incident SiH₂Cl₂ fluxes, very good agreement is observed between predicted and measured silicon growth rates.