Influence of the atmosphere on ultra-thin oxynitride films by plasma nitride process

Abstract

In plasma nitridation process for ultra thin gate dielectrics, the nitrogen concentration in the film is drastically dropped during short time after plasma nitridation process. This reduction of nitrogen before post plasma nitridation anneal process causes the Vth shift and Vth variation on the wafer. Vth shift is larger in NMOSFET. On the other hand, Vth variation on the wafer is larger in PMOSFET. The oxynitride films after plasma nitridation process should be annealed quickly to prevent Vth shift and variation. However, there must be some waiting time before post nitridation anneal process. The partial pressure of water and oxygen is necessary to be controlled during the waiting time for post nitridation anneal process. These procedures are very important for the precise control of MOSFET performance, in the generation of 65nm devices and beyond.