A kinetic model for P-type doping in silicon epitaxy by CVD

A kinetic model based on 1) the collision theory of heterogeneous unimolecular elementary reactions, 2) statistical physics, and 3) the concept of competitive adsorption is proposed for p-type doping in Si epitaxy by CVD. It takes into account an extensive set of heterogeneous reactions, which involves two precursors, SiH₄ and B₂H₆, and four types of surface sites, H-terminated Si and B sites and H-free Si and B sites. The model provides analytical equations to describe B concentration and Si growth rate as a function of deposition conditions including temperature and B ₂H₆ partial pressure. At low temperatures, the enhancement in growth rate with B₂H₆ partial pressure is attributed to enhanced H desorption from B sites, which act as catalytic sites for Si growth. The relationship between B concentration and B₂H₆ partial pressure is more complicated than a simple linear one. The model agrees well with the experimental data.