Fabrication of multilevel silicon structures by anisotropic deep silicon etching

The process of advanced silicon etching (ASE((TM))) with its possibility to pattern silicon independent from its crystal orientation has opened up a bunch of new applications in various fields such as sensor technology and micro fluidics. At IMM, a method which allows the realisation of patterns with multiple levels of almost arbitrary shapes in silicon has been developed. Using a special combination of masking layers and a dedicated process sequence, various four-level silicon structures have been realised. For example, micro fluidic devices with several regions of different depths and widths were fabricated, enabling application specific functionalities of the individual device areas. Additionally, a special post-treatment has been applied to further reduce surface roughness of sidewalls. The multilevel silicon structures can either be used directly for, e.g. complex fluidic applications, or can serve as a starting point for the Si-LiGA process, allowing the mass production of plastic micro devices. (C) 2003 Elsevier Science B.V. All rights reserved.