Automatic Cell Layout in the 7nm Era

Abstract

Multi patterning technology used in 7nm technology and beyond imposes more and more complex design rules on the layout of cells. The often non local nature of these new design rules is a great challenge not only for human designers but also for existing algorithms. We present a new flow for the automatic cell layout that is able to deal with these challenges by globally optimizing several design objectives simultaneously. Our transistor placement algorithm not only minimizes the total cell area but simultaneously optimizes the routability of the cell and finds a best folding of the transistors. Our routing engine computes a detailed routing of all nets simultaneously. In a first step it computes an electrically correct routing using a mixed integer programming formulation. To improve yield and optimize DFM, additional constraints are added to this model. We present experimental results on current 7nm designs. Our approach allows to compute optimized layouts within a few minutes, even for large complex cells. Our algorithms are currently used for the design of 7nm cells at a leading chip manufacturer where they improved manufacturability and led to reduced turnaround times.