Guidelines for Converting an Existing Library into Gridded Library

The following guidelines apply if you have to create a routing grid for a library that was not designed with a routing grid in mind, or for a library that has a routing grid designed for an older technology that needs to be reduced.

• Calculate all minimum line-to-via and via-to-via pitches for all the layers. Calculate minimum xy distances for all diagonal vias.
• Determine the routing pitch and offset for each layer by examining some cell layouts from the existing library.
  You can get the M2 preferred pitch (x coordinate) from the pin center-to-center distance of layout shapes. Getting the M1 pitch (y coordinate) might be harder because many cells in older libraries were not designed with a y pitch in mind.
• If the designed x or y pitch is larger than the line-to-via minimum, reduce the pitch.
  It might be easier to reduce the y pitch than the x pitch. Reset cell boundaries to be a multiple of the new pitch.
• Define different M1 and M3 pitches to maximize routing resources.
  Remember to use simple ratios. The cell boundary must be a multiple of both layers.
• Use rectangular vias for routing if that allows the grid you want.

Related Topics

Guidelines for Setting Pitch in a Cell Library