Migration of Selected Impurities in SiO2 Passivation Layers.
Final rept. 12 Feb 69-12 Feb 70,
BATTELLE MEMORIAL INST COLUMBUS OH COLUMBUS LABS
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The impurity content of thermally grown SiO2 passivation layers was analyzed by the ion beam mass spectrometer IBMS. The prominent impurities found were carbon, sodium, aluminum, potassium, and hydrogen. The concentration profiles for the first three impurities C, Na, Al were obtained by IBMS. These profiles show high surface concentrations of impurities with substantial concentrations in the bulk of the SiO2 layers. The migration of selected impurities Na, Al, K, Mo under high temperature conditions in the SiO2 passivation layers were studied. Samples were prepared with individual impurity deposited on the surface of the oxide. The impurity migration was produced in these samples at three temperatures 250 C, 350 C, and 400 C. The results were analyzed both by IBMS and by capacitance-voltage measurements. The concentration profiles of the impurities indicate an impurity exclusion phenomenon at the higher temperatures. All the impurities are driven out of the oxide layers at 400 C. The capacitance of MOS structures formed from the samples show improvement at 250 C, and some deterioration at 400 C. It is suggested that the existence of a sandwiched, partially-oxidized silicon layer is responsible for these divergent results. Author
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