An etch-stop technique using Cr₂O₃ thin film and its application to silica PLC platform fabrication

Using Cr₂O₃ thin film, we developed a novel etch-stop technique for the protection of silicon surface morphology during deep ion coupled plasma etching of silica layers. With this technique we were able to etch a silica trench with a depth of over 20 μm without any damage to the exposed silicon terrace surface. This technique should be well applicable to fabricating silica planar lighwave circuit platforms for opto-electronic hybrid integration.