HOMOGENEOUS NUCLEATION OF SILICON

The homogeneous nucleation of silicon from the Si-H-Cl system was stud ied theoretically for a wide range of compositions and temperatures. C ontour plots of the conversion ratio and the chemical potential to nuc leate are displayed. Nucleation rates were calculated using a modified classical nucleation model (Girshick et al. (1990) Aerosol Sci. Techn ol. 13, 465) which agrees well with reported data on the onset of nucl eation for the SiH4/H-2 and SiH2Cl2/H-2 systems. It is important to us e a correctly defined supersaturation and a temperature-dependent surf ace tension. Theoretically, the nucleation time lag is found to be sub stantial in the vicinity of the nucleation onset and at high silane co ncentrations. The decomposition kinetics of the silane becomes importa nt in systems with a very fast temperature rise, for example in a lase r-heated reactor.