Micro and nanofabrication of SiGe/Ge bridges and membranes by wet-anisotropic etching

Germanium bridges and membranes have been fabricated by lithography and wet-anisotropic chemical etching from SiGe/Ge heterostructures epitaxially deposited on Si substrates. The goal of this work is to remove completely the Si under the structures without damaging the Si material present in the SiGe alloys by using a suitable etchant. Etching by potassium hydroxide and by tetramethylammonium hydroxide solutions have been optimized in order to etch only the pure silicon underneath the structures. All the fabrication processes, to achieve free-standing structures with different shape and size, have been systematically characterized by scanning electron microscopy and μRaman spectroscopy.