LOW-PRESSURE SILICON SELECTIVE EPITAXIAL-GROWTH AND ITS THERMODYNAMICCONSIDERATIONS

In a rapid thermal processing reactor QUPLAS II, full selective epitax ial growth of silicon has been obtained using DCS in H-2 without addit ion of HCl. This is mainly achieved by reducing total process pressure down to the millibar regime. Selectivity can also be controlled by re ducing DCS gas flow rate; however, the growth rate is greatly reduced. Process temperature has, on the other hand, a minor effect on selecti vity control. The selective epitaxial growth (SEG) occurs under condit ions of near thermodynamic equilibrium. Thus equilibrium partial press ures of the predominant species in the Si-H-Cl system have been calcul ated to give an insight into the experimental results. The availabilit y of HCl species relative to silicon containing species in the gas pha se, P(HCl)/P(Si), has shown why no external HCl is required, for depos itions in millibar regime or low DCS flow rate, to obtain full selecti vity. While reaction system is near-equilibrium, the reposition of Cl, dissociated from Si containing species, into HCl species, plays an im portant role in determining the system etching function.