“Condition-based” dummy fill insertion method based on ECP and CMP predictive models

Chemical Mechanical Polishing (CMP)-aware design has become important for reliability and yield. Recent work on predictive models for wafer surface planarity of Cu CMP has proven that the variation of wafer surface planarity is impacted by the metal perimeter in addition to the pattern density. Dummy fill insertion has been widely adopted to improve the CMP planarity in industrial design flows. However, conventional dummy fill insertion has been derived mainly to optimize the pattern density uniformity, which may worsen the CMP planarity because of missing impacts due to metal perimeter. In this paper, we propose; 1) a design of experiment (DOE) based method of evaluating the quality of fill insertion by using a CMP simulator which considers the impacts due to both pattern density and metal perimeter, and 2) a condition-based dummy fill insertion using the results of the proposed DOE method. Compared to the conventional pattern density driven rule-based fill insertion, the proposed method reduces the post-CMP Cu surface height variation by 24.3%. The metric of the metal perimeter may be applied to the model-based fill insertion methods, which will improve the planarity in the practical fill insertion flow.