Pitch Routing in Abstract Generator
The pitch you choose affects the routing density. The pitch is usually a value between via-to-via spacing and line-to-via spacing.
Via-to-Via Spacing: This is the spacing required for adjacent vias and is illustrated in the figure below.
Line-to-Via Spacing: The line-to-via dimension is the distance that the routing pitch requires in order to legally place a via on the track next to a wire (line). This is illustrated in the figure below.
Adjusting the Routing Pitch: Most processes allow diagonal vias when the routing pitch is set to line-to-via. In some cases it is necessary to adjust the vertical routing pitch to allow diagonal vias. This adjustment is referred to as expanded line-to-via spacing.
Expanded line-to-via pin spacing gives better routing density than via-to-via spacing. Use via-to-via spacing only if your process requires large vias. This is illustrated in the figure below.
If diagonal vias are not allowed when using the line-to-via routing pitch, expand the routing pitch just enough to make diagonal vias allowed. The amount that the pitch must be expanded depends on the cap size of the vias.
When diagonal vias are placed, the spacing (d) must be greater than the M1-to-M1, M2-to-M2, and M3-to-M3 spacing rule, depending on the layers in the via.
Guidelines for Setting Cell Porosity and High Density in a Cell Library
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