On-grid Versus Off-Grid Blockages in Abstract Generator

On-grid blockages completely cover the grid points that are interfered with.

Slivers that result from fracturing can cause edge-to-edge spacing violations. This happens when a sliver is off-grid, as shown on the right of the figure below. The sliver covers no grid intersection points, but interferes with routing.

The blockage on the left covers three grid points and effects only one vertical routing track. This is an on-grid blockage. It allows a via to be placed without violations. The blockages on the right cover three grid points and interfere with two vertical routing tracks. The sliver also causes an edge violation with the via. The sliver is an off-grid blockage.

Libraries with no off-grid blockages allow the best routing density. The final router runs faster if all blockages within cells are on-grid.

Related Topics

Guidelines for Defining Blockages in a Cell Library