After routing at the stage of filler cells adding to the design::
can we add all spare cells in the design instead of filler cells. ofcourse filler cells will be used for N-well continuity between standard cells.
But why dont we use spare cells instead of fillers..
While fabricating the chip the fabricator should fabricate the spare cells(at transistor level) like std cells at that time also we'l have N-well continuity, then why dont we prefer spares instead fillers??
What will be the draw back if we use spares in empty places of design??
Can some one please explain....
Leakage current, compare the leakage current on a filler vs. standard cell. The lower tech nodes tend to fill first with large decoupling caps then the smaller filler cells.
Using standard cells in place of fillers may also cause some extra routing congestion because the inputs of each spare cell will need to be routed to ground.
Also, note that decap cells have power leakage as well.