Simple and Accurate Models for Capacitance Considering Floating Metal Fill Insertion

Abstract

In this paper, we analyze and model the impact of floating dummy fill on the signal capacitance considering various parameters including signal dimensions, dummy shape and dimensions. Intra-layer dummy has its greatest impact on coupling capacitance while inter-layer dummy has larger impact on the ground capacitance component. Based on this analysis, we propose simple capacitance models (Cc for intra-layer dummy and Cg for inter-layer dummy). To consider realistic cases with both signals and metal fill in adjacent layers, we apply a weighting function approach to the Cg model. We verify this model using benchmark circuits and find that total net capacitance with floating fill can be extracted within similar to 1% of field solver results on average with total extraction runtime reductions of up to 40%. When evaluating the incremental capacitance due to fill alone, average error of the models range from 2%-15% across benchmarks and fill-related runtime overhead is reduced by 60%-88%.