Nitrous oxide (N2O) processing for silicon oxynitride gate dielectrics

The gas-phase chemistry of silicon oxynitridation in N2O has been investigated. From an evaluation of available kinetic data, we have developed a model for the thermal decomposition of gaseous N2O. To quantify heat transfer between the N2O gas and the wall of the furnace, we introduce the concept of referencing to an N-2 gas-temperature profile, measured in an oxidation furnace. Using this model, we can account for the increase with flow rate and temperature of the NO concentration in the N2O decomposition product, and the self-heating during decomposition, for furnace processing. This change in gaseous NO concentration translates to a higher nitrogen content and lower growth rate for the silicon oxynitride. For rapid thermal and other short-gas-residence-time systems, we show that atomic oxygen is present at the Si wafer, and that this removes previously incorporated nitrogen.