Metal-density-driven placement for CMP variation and routability

Abstract

In this paper, we propose the first metal-density-driven (MDD) placement algorithm to reduce chemical-mechanical planarization/polishing (CMP) variation and achieve higher routability. To efficiently estimate metal density and thickness, we first apply a probabilistic routing model and then a predictive CMP model to obtain the metal-density map. Based on the metal-density map, we use an analytical placement framework to spread blocks to reduce metal-density variation. Experimental results based on BoxRouter and NTUgr show that our method can effectively reduce the CMP variation. By using our MDD placement, for example, the topography variation can be reduced by up to 38% (23%) and the number of dummy fills can be reduced by up to 14% (8%), compared with those using wirelength-driven (cell-density-driven) placement. The results of our MDD placement can also lead to better routability. © 2008 IEEE.