Fine surface processing of LiNbO₃ single crystals by maskless etching using NF₃ system gas plasma RIE

Abstract

SUMMARYThe possibility of deep etching by plasma reactive ion etching (RIE) without an etching-mask (maskless) for -Z and +Z parts formed on the same surface of a partially polarization reversed LiNbO 3 single crystal polarized in the direction of the c-axis is investigated. A NF 3 /H 2 gas mixture was used. The etching rates and depths and the profiles of the etched surfaces were evaluated by atomic force microscopy (AFM) and optical microscopy. The etching rate for the -Z surface was larger than that for the +Z surface. Extension of the +Z domain by partial polarization reversal was observed. Applying the high voltage quickly for partial polarization reversal, the area of the +Z domain was extended compared with the result obtained by applying the voltage slowly. An apparent step at the boundary between -Z and +Z parts formed on the same surface was observed. Using a NF 3 /H 2 gas mixture, the segments were removed efficiently. It is concluded that RIE etching using a NF 3 /H 2 gas mixture is suitable for processing of LiNbO 3 crystal surfaces without an etching mask, in contrast with a CF 4 /H 2 gas mixture.