Effects of RF power on BZN thin-film etching in SF6/Ar using surface analysis

Reactive ion etching (RIE) was used to etch bismuth zinc niobate (BZN) films in SF6/Ar plasma as a function of radio frequency (RF) power. Within the RF power range of choice, the etch rate of BZN films increases with increasing RF power. However, when RF power exceeds 200 W, the etch rate of films appears to increase at a slower rate. The structural properties of the BZN films before and after etching were characterized using X-ray diffraction. As-deposited film shows a cubic pyrochlore structure with preferential (222) plane orientation, but all the films etched at different reactive ion etching powers exhibit preferential (400) plane orientation. With increasing RF power, the ZnF2 phase becomes evident. Also, the film surfaces before and after etching were analysed using XPS. Metal fluorides were found to remain on the surface, resulting in varying relative atomic percentages with RF power. Zn-rich surfaces were formed because low-volatile ZnF2 residues were difficult to remove. Bi and Nb can be removed easily through chemical reactions because of their high volatility, whereas Bi-F and Nb-F, which were thought to be present in the form of a metal oxyfluoride, can still be detected using the narrow scan spectra. RF power has an effect on etch reaction through different plasma densities and particle energies, thus resulting in varying compositions and element chemical binding states. RF power also has an effect on the removal of residues. The minimum value of F atomic concentration is achieved at 150 W. Copyright (C) 2011 John Wiley & Sons, Ltd.