EPITAXIAL LATERAL OVERGROWTH OF SILICON BY CHEMICAL-VAPOR-DEPOSITION ON ULTRATHIN OXIDE LAYERS

Selective epitaxial growth followed by epitaxial lateral overgrowth (E LO) of silicon through windows in SiO2 in a hot-wall low-pressure chem ical vapor deposition system has been used to fabricate silicon-on-ins ulator (SOI) structures. By careful ex situ and in situ surface cleani ng and low-temperature processing, 2.5-mum-thick single-crystal silico n films have been successfully deposited over oxide layers as thin as 35 angstrom. Dislocation densities in these SOI films over thin oxides are higher than those found in SOI films deposited on thicker oxides. Nucleation of dislocations in the epitaxially grown film is attribute d to pinhole expansion in the ultrathin oxide layers during ex situ cl eaning, prebake treatment, or ELO processing. An unusual crystallograp hic defect with attributes of a microtwin-stacking fault complex are a lso observed in the ELO film appearing over thin oxide layers. A model is proposed to explain this class of defect structure and its formati on mechanism.