Chemical deterioration of Al film prepared on CF4 plasma-etched LiNbO3 surface

The fabrication process of an Al thin-film optical polarizer on LiNbO3 waveguides after CF4 plasma dry etching of a previously deposited SiO2 buffer layer was investigated. The problem in this process is a precipitation of compounds containing C, O, F, and Li on the etched LiNbO3 surface and a chemical deterioration of the Al caused by a reaction with these precipitates. Most notably, the growth of amorphous phase in addition to the crystalline Al metal grains and a partial oxidization of Al were found at the interface using transmission electron microscopy and x-ray photoelectron spectroscopy.