Etching characteristics of LiNbO3 crystal by fluorine gas plasma reactive ion etching

The etching characteristics of a LiNbO₃ single crystal have been investigated using plasma reactive ion etching (RIE) with a mixture of CF₄/Ar/H₂. The etching rate of LiNbO₃ with the mixture of CF₄/Ar/H₂ gases was evaluated. The etching surface was evaluated by atomic force microscopy, X-ray diffraction and X-ray photoelectron spectroscopy methods. The rate-determining process of RIE is the supply of F radicals in RIE. The surface morphology of the etched LiNbO₃ changed with the increase in the H₂ gas flow ratio. The surface profile became flat, on optimizing the etching conditions, similar to the surface of non-etched LiNbO₃. The X-ray diffraction peakfor etched LiNbO₃ using the mixture of CF₄ and Ar gases did not appear, because a non-crystalline layer was formed. It was found that the crystallinity of the surface is dependent on both, the flow rate of H₂ gas and the etching time. F atoms exist in the contamination layer of the sample etched, using the mixture of CF₄, Ar and H₂ gases. Optimum etching conditions, considering both the surface flatness and the crystallinity, were determined.