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

Abstract

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.