Ellipsometric Measurements of the Plasma Oxidation of Nb and Ta and Their Interpretation

Abstract

Ellipsometric results presented in this paper show that it is possible to grow a uniform Nb oxide film by plasma oxidation, and the index of refraction of this Nb oxide is 2.30. Similarly, in a previous paper we showed that plasma oxidation of Ta produced a uniform Ta oxide film with a refractive index of 2.21. These results are in contrast to the earlier work of Lee et al., who fitted their ellipsometric measurements on the plasma oxidation of Nb and Ta with two‐layer models. It is shown that the Nb and Ta oxides in the work of Lee et al. were not grown to a sufficient thickness to prove definitively that the oxides were composed of two layers, and that their data can be fitted equally well with one‐layer models.