Boundary Cap Cells/End Cap Placement

What is Boundary Cap (End Cap) ?

• Boundary cap cells are physical only cells. These cells are placed at the periphery of the core and power domain.
• Boundary cap cells are placed just after macro placement in the floorplan flow. These cells are placed in an array one after another.
• Boundary cap cells are placed to have N-Well tie-off. If boundary cap cells are not present in the design, then it won’t satisfy the well tie-off requirement for the core rows to prevent the foundry DRC violations.
• Boundary cap cells does not have signal connectivity. These cells connect to the power and ground rail according to the estimation of PG grid insertion.
• Boundary cap cells of different width are present in the design to manage unbreakable placement.
• Boundary cap cells are technology dependent.
• Endcap cells have dummy poly layers which help in isolating different domains and core.

In the above picture, we can see that all the boundary cap cells are sitting at the periphery of the design and within the area bounded by the boundary cap, we place Standard cells.