On lithography aware metal-fill insertion

Abstract

Manufacturability and lithographic printability are growing concerns with advancing technology nodes. The two most important parameters which influence the printability of a design are lithographic process corner and pattern density of the design. Dummy metal-fills are used to improve post-chemical mechanical polishing surface planarity. Conventional metal-fills do not consider impact of fill on lithographic printability or critical area-this is the focus of our paper. Although systematic yield due to lithographic distortions is gaining prominence, paniculate defects still remain a significant source of yield loss. Increasing design density in conjunction with growing manufacturability issues necessitates lithography aware paniculate limited yield loss analysis. In this work, we propose a novel lithography aware metal-fill insertion technique taking both statistical lithographic variations and critical area into consideration. Specifically, the main contributions of this work are a) analyzing the influence of metal-fills on line width variation and critical area, b) synthesis of variational lithography-aware metal-fill to improve design yield. The solution is been built on existing commercial tools. Experiments on ISCAS'85 benchmark circuits reveal that in 45nm technology, metal-fills worsen the linewidth variation by as much as 15% for more than 30% of nets compared to no fill. By contrast, proposed lithography aware metal-fill reduces linewidth variation by -25% and critical area by -35% compared to conventional metal-fill solutions without sacrificing density, planarity and performance targets.