Abstract
Future ULSI devices are demanding highly reliable ultra thin oxide films according to the scaling down of the minimum device dimensions. It is well recognized that contamination on silicon surface causes the degradation on the reliability of thin oxide. However, in production lines as they are now, silicon wafer after gate oxidation is transported in cleanroom air. Cleanroom air contains a large amount of organic compounds, which are come from building material of cleanroom itself. We have clarified that degradation in electrical characteristics and its non-uniformity on a wafer are caused by the contamination on silicon wafer. Further more, time-dependent degradation in gate injections for thinner gate oxide was improved by transporting wafer in N2 sealed ambient between gate-oxidation and gate-electrode-formation. We propose that future ULSI manufacturing should employ the “Closed manufacturing system”, which perfectly eliminates any contamination on wafer surface.
