Why filler cells are deleted by the tools?

[jaya sree]

Hai ,

In my project ,after cts tree is built , i have seen tool adding fill cells. then tool does clock routing ( real/global routing) . in the end tool again deletes added fill cells. why these fill cells are added? does clock routing is effected by fill cells. tool used is synopsys zroute. Options for clock routing are timing driven - true

 

[rca]

Re: deleting filler cell

The tool removes the filler cell to have place to add buffer during post route/si setup/hold steps.

 

[jaya sree]

Re: deleting filler cell

o.k but why tool is adding filler and routing clock nets? the tool can route nets without adding also right.why to add and then to delete. please clear doubt

 

[rca]

Re: deleting filler cell

some filler cells contains some metal1 blockage, so it is better to place them before routing.

 

[jaya sree]

Re: deleting filler cell

o.k thank you very much