Causes of defects and accuracy of structure reproduction in deep-etch X-ray lithography using synchrotron radiation

Under the LIGA process plastic microstructures with extraordinarily high aspect ratios are produced by means of deep-etch synchrotron radiation lithography. These microstructures are used as templates for the fabrication by electroforming of metallic microstructures. The several hundred micrometer thick resist layers required in the process are polymerized directly on a metal base plate using a methacrylate based resin. This provides sufficient stability during the production process and also a reliable plating base for the electrodeposition of the metal. Perfect adhesion of micron-sized microstructures on a smooth surface can be achieved if the polished metal surface is sputtered with titanium and chemically oxidized afterwards. Alternatively it is also possible to add an internal adhesion promoter like methacryl oxypropyl trimethoxy silane to the resin. By means of this adhesion promoter chemical bonding between the metal surface and the polymer is achieved. (orig.)