THE ORIGIN OF DEFECTS IN SIO2 THERMALLY GROWN ON CZOCHRALSKI SILICON SUBSTRATES

We have observed the origin of defects in SiO2 thermally grown on Czoc hralski silicon substrates. Samples were prepared by copper decoration to locate oxide defects, focused ion beam etching to mark them, and s ubsequent silicon-substrate thinning for transmission electron microsc ope observation. Polyhedron structures with sizes ranging from 150 to 300 nm are found in the underlying silicon-substrate surface layer jus t under the oxide defects. Two polyhedron structures superimposed on e ach other are also observed. It is believed that these structures are related to the presence of oxygen precipitates. Oxide defects are thou ght to arise due to oxide thinning induced at the edge of the silicon- substrate surface adjacent to the octahedron structures. (C) 1995 Amer ican Institute of Physics.