Mask aligner lithography is a well-established technology for microstructure fabrication. Particularly for micro-electro-mechanical systems, through-silicon vias (TSV) for 3D-IC, and advanced packaging, mask aligners are a cost effective alternative to projection lithography and an important tool due to easy handling combined with a high throughput. Based on shadow printing, mask aligner lithography has a quite simple principle of operation. A photomask pattern is transferred to wafers coated with photoresist by means of UV exposure. The mask and wafer can either be in direct contact or, in the case of proximity lithography, separated by an air gap in the range of 20 to . Contact lithography suffers from contamination, yield problems, and possible damage of the photomask. For this reason, contact lithography is not suitable for mass production. Instead, contact free proximity lithography can overcome these problems. But as the mask-to-wafer distance is increased, the resolution of the patterns transfer is decreased.