Fabrication of Free-Standing Metallic Pyramidal Shells

This paper describes a technique for fabricating three-dimensional, metallic, pyramidal microstructures with base dimensions of 1−2 μm, wall thicknesses of ∼100−200 nm, and tip-curvature radius of ∼50 nm. The procedure begins with the fabrication of pyramidal pits in the surface of an n-doped silicon substrate. An electrically insulating surface layer of SiO2 covers the regions outside the pits. These pits are patterned using either conventional photolithography or soft lithography and formed by selective anisotropic etching. The resulting topographically patterned silicon serves as the cathode for the selective electrodeposition of metal in the pyramidal pits. Removing the silicon template by etching generates free-standing, pyramidal, metallic microstructures.