Epitaxial growth of silicon on oxygen implanted substrates
The feasibility of growing epitaxial layers of silicon on silicon substrates with a buried oxide layer formed by the implantation of oxygen ions, has been studied. Conditions for epitaxial growth from a silane source in a reactor, built and commissioned as a part of the programme, have been established. Buried implanted oxide layers have been formed by high dose implantation of oxygen ions in silicon. The effects of dose at a given energy, energy for a given peak concentration, and temperature on the distribution profile of oxygen have been studied. An approximate Gaussian distribution is observed at doses contributing less than the stoichiometric requirement of oxygen for the formation of silicon dioxide. A saturation in the oxygen content is reached when the stoichiometric requirement is exceeded. A consequent reduction in the interface damage is also observed. Other parameters being equal, at higher substrate temperatures the interface damage is decreased. It has been attempted to optimise conditions for a dose of 1.4 x 1018 0+.cm-2 at 200 keY which provides the stoichiometric concentration only at the peak of the distribution. The epitaxial layers deposited on substrates maintained at 5500C during implantation have a crystalline quality comparable to those of layers on untreated substrates. Fabricated p-n junction diodes have low leakage currents and high breakdown voltages. The minority carrier lifetime is comparable to that in diodes processed similarly but without an implanted oxide layer.