Sensitivity of ellipsometric modeling to the 'islands' of silicon precipitates at the bottom of the buried oxide layer in annealed SIMOX

Spectroscopic ellipsometry as a nondestructive probe for multilayer SIMOX materials is considered. TEM micrographs of high flux single implant SIMOX annealed at 1300 degrees C for 6 h show islands of silicon precipitates near the bottom of the buried oxide layer. Spectroscopic ellipsometric measurements were performed on these samples at various implant doses and beam current densities to observe how the measured data fit the data theoretically predicted for various models of SIMOX that lead to the presence of these islands. Three distinct models of increasing complexity were used in the analysis: a 3-layer model having a silicon dioxide cap layer, upper silicon layer, and buried or implanted silicon dioxide layer; 4-layer model in which a new layer between the silicon substrate and buried silicon dioxide was added where the islands exist; and a 5-layer model that raised the island layer off the top of the substrate by adding a thin pure silicon dioxide layer above the substrate.<
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