Formation of inverse cones in crystalline silicon by selective etching of amorphous regions resulting from epitaxial breakdown

We report on a process to form micron-scale inverse cones in crystalline silicon without any masking steps using selective, low temperature (<175°C) plasma process. The selectivity of the originates from use H 2 that preferentially etches away amorphous cones, formed as result epitaxial breakdown, leaving surrounding material behind. Efficient etching is realized by pre-coating reactor walls with hydrogenated oxide (a-SiO x :H) prevent chemical transport towards substrate. etch depth linked directly time exposure plasma. When densely packed, such structures exhibit useful optical properties, specular reflectance 2% (with sample appearing visibly black high density and fully etched regions) iridescence (in regions partial etching).