Post-layout timing-driven cell placement using an accurate net length model with movable Steiner points

This paper presents a new algorithm for timing-driven cell placement using the notion of movable Steiner points that capture the net topology. The proposed algorithm improves the timing closure at the backend of the EDA design flow. Unlike conventional flows that perform placement and routing in two separate steps and use rough estimates of the net lengths during placement, our algorithm uses accurate net lengths by considering the net topologies during the Elmore delay calculation step and dynamically updates the routing during the concurrent placement of Steiner points and cells. The simultaneous placement and routing problem is formulated as a mathematical program with a small number of variables and solved by the Han-Powell method. Experimental results demonstrate the effectiveness of the new approach compared to the conventional flows