Nitrous oxide (N ₂ O) processing for silicon oxynitride gate dielectrics

Abstract

The gas-phase chemistry of silicon oxynitridation in N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O has been investigated. From an evaluation of available kinetic data, we have developed a model for the thermal decomposition of gaseous N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O. To quantify heat transfer between the N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O gas and the wall of the furnace, we introduce the concept of referencing to an N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> 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 N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O 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.