Effect of ambient air infiltration on growth rate and electrical characteristics of ultra-thin silicon dioxide gate insulators

Effective chemical cleaning of silicon surfaces prior to gate oxidation is critical in ensuring reliable gate oxide integrity. Of equal importance is the ability to keep the silicon surface free of any contamination during subsequent thermal processing. During the thermal oxidation of silicon, Ambient Air Infiltration (AAI) has been shown to be a significant source of wafer-to-wafer and within wafer thickness variability. AAI has also been shown to be a major factor in affecting the total oxide charge. Increasing reactant gas flow rates, processing the wafers in encapsulated cantilevers, optimum placement of gas baffles, and controlling reactor exhaust rates have helped reduce ambient air infiltration and the detrimental effects of this source of contamination.