In the first step of the LIGA process a resist layer, typically PMMA (polymethylmethacrylate), is pattered by deep X-ray lithography. The exposed parts are subsequently dissolved by an organic developer. The quality and the achievable height of the microstructure is decisively determined by the development process. In order to increase the aspect ratio and maintain the quality of the microstructures the parameters influencing the development process were investigated. In the case of dip development and ultrasound development a strong dependency of the development rate on the temperature, dose value and depth of deposition has been noticed. The development rate increases with increasing dose value and temperature and decreases with increasing depth of deposition. In case of dip development the development course can be described by a phenomenological equation which considers the three mentioned parameters. In the case of ultrasound further parameters have to be taken into account: the geometry and the dimensions of the strucutres.

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The fabrication of high aspect ratio microstructures using the X-ray lithography and electroplating step of the LIGA process requires, that the metal layer on the substrate (plating base) enables a¯awless resist adhesion and provides a high conductivity for the following electroplating process. In addition, a¯awless metal adhesion after electroplating has to be ensured. Typically metal layers of titanium, but also of copper and gold are used. In case of higher structures,¯uores-cence radiation generated in the metal layer during exposure reduces the bond strength between the resist and the adhesion layer [7]. Since the¯uorescence probability decreases with a decreasing atomic number, the suitability of conductive carbon as the plating base was investigated and compared to results achieved with titanium. The resist adhesion was increased tremendously on the carbon layer but the metal adhesion is insuf®cient. Therefore, platinum islands were deposited on the conductive carbon to facilitate good metal adhesion. The resulting resist adhesion was still superior compared to titanium. In addition, metal adhesion was achieved on these layers.

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