Fabrication of macroporous polysilicon by nanosphere lithography

The fabrication of ordered macroporous silicon is obtained by exploiting the self-assembly properties of polymer nanospheres. Here, we demonstrate the method by using nanospheres of 200nm and 500nm. These self-assemble in monolayers of ordered hexagonal close-packed nanospheres. A controlled reactive ion etch of the assembled nanospheres, subsequent evaporation of metal, followed by 'lift-off' of the polymer nanospheres, provides a mask suitable for a further reactive ion etch step to provide macroporous polysilicon. This methodology provides a novel approach for the fabrication of highly ordered macroporous polysilicon; porous silicon substrates with pores of this size (50nm to 500nm) were previously only fabricated using rather difficult processing methods. The method reported here is straightforward and achieved using fabrication methods that are compatible with those currently used for microelectromechanical systems (MEMS), photonic devices and nanostructured surfaces