Dependence of crystal structure and work function of WNx films on the nitrogen content

Abstract

The effect of nitrogen content on crystal structure (phase and grain size) and work function (Φm) of WNx films is investigated. The Φm of WNx films is extracted from the plot of flatband voltage versus SiO2 thickness. For W and WN0.4 films, the Φm are 4.67 and 4.39V, and their crystal phases are both body-centered-cubic W. For WN0.6 film, it contains W+W2N mixed phases and the Φm is 4.50V. On the other hand, the Φm of WN0.8 and WN1.5 films are 5.01 and 4.49V, and their crystal phases are both face-centered-cubic W2N. The grain size of W and W2N phases decreases with the increase of the nitrogen content in WNx. It is concluded that the Φm is affected by the crystal phase as well as the grain size of WNx film.