Impact of high resolution lithography on IC mask design

Not only are shrinking device dimensions placing increasing technology challenges on existing lithography processes, but they are also forcing changes in the layout and masking approaches that support them. The need to extend traditional optical lithography to 180 nm using resolution enhancing technologies such as optical proximity correction (OPC) or phase shift masks (PSM) generally requires the use of pattern modifications that are not part of the original design layout. Furthermore, implementation of new post-optical lithography techniques may require significant changes in reticle layout formats in addition to fundamental material and process changes. For example, new formats are required for masked E-beam (SCALPEL) and ion projection lithography reticles, while very high resolution OPC appears to be necessary to extend 1X X-ray lithography below 100 nm. However, unlike the case with OPC and PSM extensions for optical lithography, design tools to support new post-optical patterning formats have not yet been developed.