Dry etching charactristic of LiNbO₃ in plasma

Abstract

As the microfabrication technique of LiNbO₃ that utilized electric field sensor, the wet etching by fluorine acid solution and the dry etching by plasma have been used. However, etching condition and etching profile need to be examined in detail. We have studied a plasma etching characteristic of LiNbO₃. The etch rate of LiNbO₃ increases drastically by interaction of physical and chemical etching. The maximum etch rate was 31.8nm/min for 60% Ar in CF₄+Ar plasma and 29.6nm/min for 37% H₂ in NF₃+H₂ plasma. This etch rate increases by 3 times in comparison with that in CF₄ only plasma and 10 times in comparison with that in fluorine acid solution (10%). The analytical results by XPS show that LiNbO₃ absorbs F radical and forms the mixing layer in the surface and the etch rate of LiNbO₃ increases by the ion bombardment effect. It is found out that Ni metal is adequate as the mask material. The Ridge type optical waveguide with the height of 3μm could be formed.