Si (100) and Si (311) - A comparative study for nanofabrication

Bulk micromachining was mainly developed for Si (100) and Si (110) wafers and is based on crystallographic etching of silicon in KOH and other basic solutions, in order to obtain useful 3-dimensional structures. Recently, Si (311) joined the group of useful substrates for nanomanufacturing, but a thorough description of its capabilities was not yet reported. The hereby study investigates the particularities of crystal-orientation dependent etching of Si (311) wafers in comparison with Si (100) in some of the most popular solutions used for etching. By that, the experimental study adds to the base of knowledge of Si anisotropic etching and diversifies its capabilities. Of particular interest is Si (311)´s capability to form V-grooves of three-faceted pyramid shape, useful for forming wedge-free tips for subsequent molding, which can be exploited to form tips with sub-10 nm apex radii.