Alternative resist adhesion and electroplating layers for LIGA process

The fabrication of high aspect ratio microstructures using the X-ray lithog raphy and electroplating step of the LIGA process requires, that the metal layer on the substrate (plating base) enables a flawless resist adhesion an d provides a high conductivity for the following electroplating process. In addition, a flawless 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, fluorescence radiation generated in the meta l layer during exposure reduces the bond strength between the resist and th e adhesion layer [7]. Since the fluorescence probability decreases with a d ecreasing atomic number, the suitability of conductive carbon as the platin g base was investigated and compared to results achieved with titanium. The resist adhesion was increased tremendously on the carbon layer but the met al adhesion is insufficient. Therefore, platinum islands were deposited on the conductive carbon to facilitate good metal adhesion. The resulting resi st adhesion was still superior compared to titanium. In addition, metal adh esion was achieved on these layers.