Pushing the limits of macroporous silicon etching

We present a detailed investigation of the fabrication of almost perfect three-dimensional microstructures grown by a photoelectrochemical etching process. The focus is directed on the physical effects that have limited the achievable pore shapes to very smooth modulations. These limits can be overcome by an improved etching process allowing strongly modulated three-dimensional networks. In particular, the chronology of the growth of a single modulation is shown.