Progress in graytone lithography and replication techniques for different materials

The fabrication of 3D-microstructures with well-defined curved surface contours is of great importance for various mechanical, optical and electronic devices and subsystems. Complex geometrical structures or topographies are necessary to obtain a certain mechanical stability, a specific surface property or a predetermined electrostatic field configuration. Obviously in the micro-optic domain, there is a great demand to produce sophisticated surface topographies for refractive or diffractive optical elements, e.g. Fresnel lenses. This paper reports on progress in graytone lithography using subresolution pixeled chromium glass masks and introduces some replication techniques for different materials. In continuation of our work on graytone lithography, reported elsewhere [5,6], detailed view on reproducibility, fidelity and process latitude will be presented. Based on this results infrared diffractive optical elements have been fabricated in silicon using an 1:1 dry etching process, where the surface roughness of the shaped areas after etching has an lo value of 18 nm. For low cost application in the visible wavelength region a replication technique in polycarbonat by injection molding is described. First results are shown.