Silicon deposition from disilane on Si(100)-2x1: Microscopic model including adsorption

We present a model for the calculation of homoepitaxial film growth rates d uring silicon deposition on Si(100)-2x1 from disilane. Central to this mode l is the use of thermalized gaseous disilane adsorption probabilities that have been determined as a function of gas and surface temperature by convol uting supersonic molecular beam adsorption probability data with a Maxwell- Boltzmann distribution of incident kinetic energies and angles. These calcu lations show that the primary adsorption pathway over the entire range of c onditions investigated is the so-called trapping-mediated mechanism, in whi ch dissociative chemisorption occurs via a physisorbed intermediate. A seco nd adsorption mechanism, direct chemisorption, is activated by translationa l energy and does in fact contribute somewhat to adsorption, but only at hi gh gas and surface temperatures. Hydrogen coverages and silicon film growth rates are calculated from a simple surface decomposition kinetic model tog ether with a phenomenological thermal desorption model and compare favorabl y to experimental measurements. Under conditions of high flux or low surfac e temperature, the growth rate is limited by hydrogen desorption and theref ore increases with increasing surface temperature. In the flux-limited or a dsorption-limited growth regime, the growth rate is predicted to decrease w ith increasing surface temperature due to a drop in the adsorption probabil ity, resulting in a maximum in the growth rate for a given set of depositio n conditions. (C) 2001 American Institute of Physics.