Simulation tools for advanced mask aligner lithography

Contact- and proximity lithography in a Mask Aligner is a very cost effective technique for photolithography, as it provides a high throughput and very stable mature processes for critical dimensions of typically some microns. For shadow lithography, the printing quality depends much on the proximity gap and the properties of the illumination light. SUSS MicroOptics has recently introduced a novel illumination optics, referred as MO Exposure Optics, for all SUSS MicroTec Mask Aligners. MO Exposure Optics provides excellent uniformity of the illumination light, telecentric illumination and a full freedom to shape the angular spectrum of the mask illuminating light. This allows to simulate and optimize photolithography processes in a Mask Aligner from the light source to the final pattern in photoresist. The commercially available software LayoutLab (GenISys) allows to optimize Mask Aligner Lithography beyond its current limits, by both shaping the illumination light (Customized Illumination) and optimizing the photomask pattern (Optical Proximity Correction, OPC). Dr.LiTHO, a second simulation tool developed by Fraunhofer IISB fro Front-End Lithography, includes rigorous models and algorithms for the simulation, evaluation and optimization of lithographic processes. A new exposure module in the Dr.LiTHO software now allows a more flexible definition of illumination geometries coupled to the standard resist modules for proximity lithography in a Mask Aligner. Results from simulation and experiment will be presented.