Interest in thick-photoresist applications is steadily growing. In addition to bump fabrication and wire interconnect technology (WIT), the process of patterning thick-layer photoresists by UV lithography is specially qualified for applications in microelectromechanical systems (MEMS). Specialized equipment and new photoresists have been developed or are under development to cope with the new challenges in the field of preparing extremely thick photoresist layers, the process of patterning these thick resists, and to deal with the difficulties of the following galvanoplating step. As one of the most critical steps in thick-photoresist processing, the baking procedure was investigated. Positive tone photoresists (AZ 4562, maP 100) were processed by means of three different baking methods: air-forced oven, ramped hotplate, and IR radiation. It could be shown that IR baking is advantageous compared to the other methods with respect to process duration and energy consumption. As for edge steepness, resolution, edge loss, and surface roughness, all methods deliver nearly the same results. A minimum width of 2-3 µm for the resist bars was found to be necessary to withstand the fabrication process of lines and spaces in about 15 µm thick resists. For thicker layers, high aspect ratios of about 10 as well as steep edges of more than 88 • could be fabricated. The development of SU-8, a chemically amplified negative tone photoresist for the 300-450 nm region opened totally new dimensions for the UV depth lithography. Even under development, SU-8 delivers results otherwise only achievable by x-ray lithography. The deposition of photoresist on highly-structured surfaces demands advanced methods. Electrodeposition of resist is one solution. PEPR 2400 was used for patterning by UV light in order to generate resist patterns around a free standing silicon bar. The achieved resist patterns were moulded by using electroplating. For microsystem applications some metals and alloys were deposited. Three-dimensional micro components were fabricated as demonstrators for the new technique. Electrodeposition allows the use of materials with interesting properties which could not be provided by standard processes in microelectronics.

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SU-8 is an essential material for manufacturing micromechanical components with high demands in aspect ratio and toughness in the area of micro-system technologies. For reproducible production of SU-8 components, e.g. polymeric AFM-cantilevers and chip carriers, a characterization sequence for the material in its raw state and in all subsequent processing steps was developed. Included in these tests were differential scanning calorimetry of the unprocessed resist, in situ monitoring of the solid content during soft bake, measurement of the stress behaviour during and after post-exposure bake as well as determination of micro-hardness and Young's modulus at different baking and exposure conditions. The results are promising with respect to definition of a novel procedure for reproducible preparation of micromechanical components from SU-8.

Here we present an approach for creating full-color digital rainbow holograms based on mixing three basic colors. Much like in a color TV with three luminescent points per single screen pixel, each color pixel of initial image is presented by three (R, G, B) distinct diffractive gratings in a hologram structure. Change of either duty cycle or area of the gratings are used to provide proper R, G, B intensities. Special algorithms allow one to design rather complicated 3D images (that might even be replacing each other with hologram rotation). The software developed ("RainBow") provides stability of colorization of rotated image by means of equalizing of angular blur from gratings responsible for R, G, B basic colors. The approach based on R, G, B color synthesis allows one to fabricate gray-tone rainbow hologram containing white color what is hardly possible in traditional dot-matrix technology. Budgetary electron beam lithography based on SEM column was used to fabricate practical examples of digital rainbow hologram. The results of fabrication of large rainbow holograms from design to imprinting are presented. Advantages of the EBL in comparison to traditional optical (dot-matrix) technology is considered.

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