The Study of Latex Sphere Lithography for High Aspect Ratio Dry Silicon Etching

摘要

A method to obtain vertically aligned silicon structures with a high aspect ratio,which are interesting for photovoltaics, using nanosphere lithography andcryogenic plasma etching is explored. For the conventional nanosphere lithography,the etching of the latex spheres during the cryogenic plasma process limitsthe maximum ratio of Si wire length to the diameter at the level of 5:1. Themaximum length of 2–3 μm can be obtained for Si wires with 0.45 μm diameter.An intermediate step of SiO_2 hard mask formation before nanosphere lithographyis proposed to increase the maximum length. The nanosphere lithography withthe predeposited SiO_2 layer allows to increase the maximum length/diameterratio to at least 15:1. An array of Si wires with a diameter of 0.45 μm and a lengthof 6 μm is obtained on the entire surface of 4 in. Si wafers.