Comprehensive process for low temperature epitaxial growth

Abstract

A system and method for growing low defect density epitaxial layers of Si on imperfectly cleaned Si surfaces by either selective or blanket deposition at low temperatures using the APCVD process wherein a first thin, e.g., 10 nm, layer of Si is grown on the surface from silane or disilane, followed by the growing of the remainder of the film from dichlorosilane (DCS) at the same low temperature, e.g., 550.degree. C. to 850.degree. C. The subsequent growth of the second layer with DCS over the first layer, especially if carried out immediately in the very same deposition system, will not introduce additional defects and may be coupled with high and controlled n-type doping which is not available in a silane-based system. Further, in order to achieve an optimal trade-off between the need for an inert ambience to promote silane reaction at low temperature and the need for a hydrogen ambience to prevent surface oxidation from inadvertant residual impurities, depositions are carried out in an ambience composed primarily of He but always containing some H.sub.2. Also, the relative deposition rates on a patterned surface of polycrystalline Si on insulator areas and single crystal Si on single crystal seed areas, when using the reactant silane, are dependent on the temperature of deposition and the relative concentrations of hydrogen and inert gas, e.g., helium, in the ambient gas, and can be controlled by regulating these parameters.