Challenges in electron cyclotron resonance plasma etching of LiNbO3 surface for fabrication of ridge optical waveguides

Ridge-shaped optical waveguides are promising structures to provide broadband characteristics for LiNbO3 (LN) based optoelectronic devices. In this regard, electron cyclotron resonance plasma etching with fluorocarbons have been commonly applied in the preparation of ridge waveguides, 3-5 mu m in height, but certain fabrication problems need investigation and clarification. The etched LN surface was found to be covered with LiF leading to a weak adhesive strength for the overlayer, such as a SiO2 film, over the ridge waveguides. When CF4 etchant was used, a notch appeared along the foot of the ridge waveguides. The notch was a possible origin for the chipping of the waveguides, Such an undesirable notch was found to be prevented by the use of a CHF3 etchant. Here, these inevitable problems during the plasma etching of the LN were presented and discussed. (C) 1998 American Vacuum Society. [S0734-2101(98)11204-6].