Definition of an innovative filling structure for digital blocks : the DFM filler cell

A DFM approach considers all interactions in the production flow and breaks the standard local/global context. Understanding existing solutions and their limitations in filling solution for digital blocks, we present in this paper a DFM filler cell solution that takes into account a large amount of problems that can be encountered at many steps of the production flow, such as lithography or planarity variations, while other kinds of filler cells only solve density problems. This allows designs to be less dependent on the global context of the digital block. Our DFM filler cell reduces the STI width stress impact, contains dummy polysilicon gates that allow an OPC-friendly approach and is more flexible for the place and route step. Our approach was validated by a silicon structure and many published data in this domain. The insertion of DFM filler cells is costless in terms of area thanks of their size that are multiple of the grid size. Furthermore, the usage of DFM filler cell in the complete design flow was validated.