OPTICAL-CONSTANTS OF SPUTTERED HAFNIUM NITRIDE FILMS - INTRABAND AND INTERBAND CONTRIBUTIONS

Transparent and opaque films of hafnium nitride have been prepared by reactive magnetron sputtering in an argon-nitrogen atmosphere. The fil ms were deposited upon healed Coming glass substrates with a depositio n rate of about 2.1 nm/s. The optical constants of the films were calc ulated using Kramers-Kronig integration and ellipsometry for the opaqu e samples and a combined R/T method for transparent samples. Detailed observation of the thickness variation in the optical constants reveal ed a clear trend: larger n-values and smaller k-values in the VIS-and NIR-range for thinner films. This was analysed within the framework of the classical Drude model and found to be an effect of shorter relaxa tion time for thinner films. The effect is as large as a factor of thr ee in the film thickness interval 15-380 nm. The optical effective mas s of the d-electrons was found to be in the interval 0.82-0.95 of the free electron mass, which is significantly lower than in TiN but simil ar to ZrN. The interband contribution to epsilon(2)(omega) was obtaine d by subtraction of the Drude part from the experimental dielectric fu nction. It exhibits a sharp increase for lambda < 400 nm, indicating t he threshold for interband transistion.