COMPOSITIONAL STUDIES OF THERMALLY NITRIDED SILICON DIOXIDE (NITROXIDE)

The kinetics of thermal nitridation of silicon dioxide in ammonia ambient has been studied. SiO//2 films of 100-1000A thick were thermally nitrided at 950 degree -1100 degree C for times from 15 sec to 2 hr. Experimental results based on etch rate and Auger electron spectroscopy measurements clearly indicate the multilayer structure of nitrided-oxide films. Nitrogen-rich layers are formed at the surface and interface regions at a very early stage of the nitridation process. After a few minutes, the nitridation reaction mainly goes on in the bulk region, with the surface and interface nitrogen content remaining fairly constant. The Auger depth profiles show that the interface moves away from the nitrogen-rich layer as the nitridation proceeds. In addition, results indicate the formation of an oxygen-rich layer underneath the nitrogen-rich layer whose thickness increases with nitridation time.