Three Litho-Process-Litho Approaches for 2D Double Patterning at the 32nm Half Pitch Node

Various material approaches for more cost-effective double patterning have been proposed during the past few years. Resolution capabilities of these approaches using dipole illumination are documented in literature. In this paper it is investigated whether these novel materials may also be applied for printing of more random structures at the 32nm half pitch using annular illumination. As expected process windows with more relaxed illumination conditions are observed to decrease. The CD bias of Litho1 features throughout the double patterning process is observed to vary more under annular illumination compared to dipole. This has important implications for the process window of the Litho1 target. Nevertheless, excellent CDU results are obtained for all three processes. LWR is shown to be high, which can be mainly attributed to the illumination setting and is not inherent to the materials. Finally a demonstration of the printing feasibility of turns and stitching in selected logic and DRAM structures is given. The poly-Si etch capabilities of the alternative processes is also shown.