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

摘要

The effect of nitrogen content on crystal structure (phase and grain size) and work function (Φ_m) of WN_x films is investigated. The Φ_m of WN_x films is extracted from the plot of flatband voltage versus SiO_2 thickness. For W and WN_(0.4) films, the Φ_m are 4.67 and 4.39 V, and their crystal phases are both body-centered-cubic W. For WN_(0.6) film, it contains W+W_2N mixed phases and the Φ_m is 4.50 V. On the other hand, the Φ_m of WN_(0.8) and WN_(1.5) films are 5.01 and 4.49 V, and their crystal phases are both face-centered-cubic W_2N. The grain size of W and W_2N phases decreases with the increase of the nitrogen content in WN_x. It is concluded that the Φ_m is affected by the crystal phase as well as the grain size of WN_x film.