On the silicon dioxide/polycrystalline silicon interface width measurement

The apparent width of the SiO2Si interface was evaluated with Auger electron spectrometry, secondary ions mass spectrometry and transmission electron microscopy for thin silicon dioxide films grown at temperature ranging from 900 to 1100°C, both on single- and poly-crystalline silicon (polysilicon), with the aim of finding the meaning of this kind of measurement for this particular system. The width of the transition between SiO2 and polysilicon was found to depend on both the oxidation temperature and polysilicon doping method, being lower for ion implanted than for gas phase (POCl3) doped samples and for oxides grown at higher temperature. The possible causes for the differences in the interface width are discussed and attributed, in the present case, to the oxide thickness non-uniformity. This is due, in turn, to the lower oxide growth rate, particularly for the lower oxidation temperature, on the silicon grains protruding out of the surface.