D2S, Inc. (San Jose, CA) has introduced TrueMaskTM DS, the industry’s first mask‐wafer double simulation accelerated workstation for R&D exploration, bit‐cell design, hot‐spot analysis, and mask‐defect categorization that comprehends overlapping eBeam shots and dose modulation. TrueMask DS is an ideal tool for mask shops and wafer fabs in qualifying and optimizing 20‐nm‐node and below designs, where assist features on photomasks that are smaller than 80 nm in size can no longer be produced faithfully and have an increasing impact on wafer yields. Deploying hardware acceleration, TrueMask DS can produce a double simulation of the mask and wafer for 5x5 micron (on wafer) areas at interactive speeds. Users can experiment using different variable‐shaped beam (VSB) shots to write the masks, as well as using overlapping shots and dose modulation—techniques that can be employed to reduce mask write times and improve CD uniformity, respectively. Then, users can instantly see the contour shape of the exposed resist, and within seconds see an overlay of the lithography aerial image that would be printed on the wafer.
TrueMask DS features include 0.1‐nm‐resolution mask simulation up to 300x300 micron (mask dimensions), including overlapping shots and dose modulation; advanced eBeam modeling with arbitrary point spread functions for exploration; fast, interactive aerial litho simulation from hardware acceleration; 5x5 micron (on wafer) interactive mask‐wafer double simulation; and SEM interface for overlay analysis of pictures with simulations.