SPIE Journal Paper | 1 January 2005
KEYWORDS: Mirrors, Spatial light modulators, Reticles, Maskless lithography, Photomasks, Semiconducting wafers, Scanners, Wafer-level optics, Lithography, Raster graphics
We review the current status of optical maskless lithography technology. The optical maskless systems presented in literature are either aimed for low-cost, large-feature, low-end production, or high-end performance directly competing with state of the art optical scanners. In the latter case, optical maskless systems are based on piston or tilting micromirror spatial light modulators (SLMs). Similar performance can be achieved with both mirror types, but tilting mirrors offer lower manufacturing complexity, the possibility of using larger mirrors, less complex rasterizing algorithms, and lower demands on the data path. This indicates that the tilting mirror arrangement might be more appealing for high-performance, high-capacity, economical optical maskless lithography. With the latest technology in SLM and rasterizing technology, an optical maskless tool can match regular mask-based scanners in all imaging modes at the 65-nm node, including binary, weak and strong phase-shifting, phase edge, and chromeless phase lithography. Optical maskless lithography can further provide an almost complete transparency with current lithography technology in terms of design rules, optical proximity correction (OPC) models, and illumination settings. Any difference is due not to the SLM, but to the reticle process and electromagnetic properties.
