Improving the lithographic process window using directed self-assembly-aware printing assist features

Variation in the shape of directed self-assembly (DSA) prepatterns caused by lithographical process variability is one of the significant contributors to the placement error in DSA patterning. DSA-aware printing assist features (PrAFs) can be used to reduce the sensitivity of DSA prepatterns to lithographical process variability, with the printed sidelobes resulting from these PrAFs being “sealed” during the DSA step of the process. For instance, in a graphoepitaxy DSA process, where confinement wells are formed by deep ultraviolet (DUV) lithography, the process window of the DUV lithography process may be improved by using PrAFs, as long as the confinement wells resulting from these PrAFs are sized and shaped so that they do not etch transfer into the substrate due to etch-resistant outcomes of the DSA process. A method to optimize the placement of these DSA-aware PrAFs is presented, along with a method utilizing a regular array of etch-resistant confinement wells with localized modifications of their size or shape to form etch-transferrable features. Both methods are tested and verified in simulations of DUV lithography and DSA.