Effects of SF6/Ar gas-mixing ratio on the etching behavior and properties of BZN thin films

Abstract

Bismuth zinc niobate (BZN) thin films were etched as a function of the SF6/Ar gas-mixing ratio in a reactive-ion etching (RIE) system. The etching characteristics of surface etch rate and compositions were investigated. Within the ratio range of choice, the etch rate of BZN films is found to decrease first and then increase as the ratio decreases. The small error bars shown in the line graph present a high reliability of the etch rate data. BZN films surfaces were investigated by X-ray photoelectron spectroscopy (XPS). Metal fluorides were found to remain in the surface, resulting in varying relative atomic percentages with gas-mixing ratio. Zn-rich surfaces were formed for ZnF2 residues were hard to remove. Bi and Nb can be removed easily through chemical reactions because of their high volatility, while BiF and NbF can be still detected using narrow scan spectra, which were thought to be present in the form of a metal-oxy-fluoride (Metal-O-F). Gas-mixing ratio is found to have an effect on etch reaction and the removal of residues through different plasma ratios etch process, therefore, leading to varying compositions and element chemical binding state, and resulting in the AFM surface morphology and dielectric property variation. The minimum value of F atomic concentration is achieved at SF6/Ar ratio of 32/13, while the lower surface roughness and the greater dielectric constant both appear at the ratio of 40/5.