3. Placement Optimization for DSAL

In DSAL, each group of contacts (or vias) is associated with a GP. The number of member contacts and their relative position determine the shape of GP. Some GPs, for instance of those with asymmetric shape, have high DSA defect probability as addressed in Sect. 2.​2, and have to be avoided. In standard cell based design, if such GPs are discovered within a cell, library designers are responsible to fix. If they are discovered at cell boundary when two cells are abutted after placement, a simplest approach to fix is to insert whitespace. It turns out that too many cell pairs require whitespace. In this chapter, two placement techniques are presented. In post-placement optimization (Shim et al., in Proceedings of the International Conference on Computer Aided Design, pp. 404–409, 2015, [1]), some cells are flipped and some two cells swap their position so that the number of cell pairs that require whitespace is minimized. In automatic placement, defect probability is taken care of while placement is performed. It is demonstrated that the two techniques yield layout of higher density (or less whitespace) by about 11–12% compared to layout of simple-minded approach.