Change in depth profile of N highly incorporated into SiO2 by plasma-assisted nitridation

Abstract

The depth profile in nitrided SiO2 films using N2 remote radio frequency plasma was investigated. N was incorporated into the film at levels of up to 27 atom %, largely concentrated at the film surface, and not the film interface. The depth profiling data showed that the depth of incorporated N is dependant on film thickness, i.e., N is incorporated to a depth of about 1.1 nm in a 1.5 nm thick film, while the depth is significantly less to about 0.7 nm in the case of a 4.0 nm thick film. Moreover, under the same nitridation condition, more N content is concentrated nearer to the surface of a 1.5 nm thick oxide film than that of 4.0 nm thick film. N2, generated in the molecule during the nitrogen process is almost completely concentrated at the film interface. After an additional annealing treatment, the molecular N2 diffuses out extensively and N, which is chemically bonded to Si3, is changed into a more stable state with different second-nearest neighbors, accompanied by reoxidation at the film interface of an ultrathin film. © 2006 The Electrochemical Society. all rights reserved.