CLARIFICATION OF NITRIDATION EFFECT ON OXIDE FORMATION METHODS

The electrical characteristics of gate dielectrics have been intensive ly studied. We examined four types of gate dielectrics: thermal oxide films formed in a pyrogenic steam ambient, those in a dry oxygen ambie nt: chemical vapor deposition (CVD) oxide films, and the thermal/CVD s tacked oxide films. The effects of nitridation on oxide properties hav e been also systematically investigated using the nitrogen implantatio n technique. It is found that hot-carrier degradation can be improved by nitridation irrespective of the oxidation methods. This improvement is attributed to the suppression of interface state generation and th e reduction in the number of electron traps in the oxide films. Our ex tensive investigation concludes that the nitridation of gate oxide fil ms by nitrogen implantation is very promising for the improvement in r eliability in spite of the difference in oxide formation methods.