A TEM INVESTIGATION OF THE EFFECT OF ANNEALING ON SINGLE-CRYSTAL SILICON-OXIDE POLYCRYSTALLINE SILICON INTERFACES

(001) silicon slices were given a chemical treatment to produce a surface oxide layer approximately 10 angstrom thick. A polycrystalline silicon (polysilicon) layer 1000 angstrom thick was grown on each slice at 620-degrees-C, implanted with 5 x 10(15) cm(-2) 30 keV As+ ions, and annealed in dry oxygen at 1000-degrees-C for various times. Such treatment causes the oxide layer to break-up and the polysilicon layer to grow epitaxially on the silicon slice through gaps found in the oxide layer. This behaviour is important in the fabrication of polysilicon emitter bipolar transistors. Detailed transmission electron microscope (TEM) and high resolution electron microscope (HREM) studies have been performed on these slices to determine the structures initially present at the single-crystal silicon/oxide/polysilicon interface, and the manner in which these changed as the annealing proceeded. The size, shape and number density of the resulting oxide particles were obtained, and it was shown that the total volume of the particles remained closely the same. Crystallographic defects occurring in the epitaxially re-grown polysilicon layer often nucleated at the oxide particles.