To faithfully transfer nanostructures from one material to another, anisotropic etching  is generally favored over wet chemical etching because it has much better anisotropy, steeper side walls, less undercutting, less dependence on the crystal orientation, and better controllability.  We have reactive ion etching (RIE) and chemical assisted ion beam etching systems (CAIBE).  Our objective in etching research is to develop dependable recipes for sub-50 nm etching of semicoductors, insulators, and metals, with  a high anisotropy and excellent size control.  Currently, we have acheived 10 nm diameter pillars of 60 nm height in both Si and SiO2, and 100 nm wide lines in metals.