Gridded Placement of Integrated Unit Cells for FEOL Fill

Abstract

Using swap/unit cells in FEOL Fill is a widely practiced method because of the placement algorithm simplicity. Over the last several years, Fill engineers devised intelligent ways to find multiple optimum sized swap cells and have been placing them sequentially to achieve higher Fill density. In cutting edge FinFET technologies nodes, however, such swap cell approach cannot meet the aggressive process requirements, such as demanding density, and due to inter-layer dependencies in FEOL swap cell.To overcome this challenge, GLOBALFOUNDRIES (GF) Fill algorithm has removed dummy Fin from swap cells to place at the very beginning of FEOL Fill routine. The subsequent cells align with previously placed "Fin-grid". Such adaptation ensures meeting the process requirements of surrounding FEOL Fill layers by RxFin, while a higher FEOL Fill density is achieved with a high efficiency. Along this line, the associated implementation choices and the corresponding tradeoffs are discussed.