Can we add the FILLER cells after routing completed

Hello Mastaru !! ,

One should do FILLER cell addition before GDS strimout ( i.e after fixing DRC by P&R [after routing] )

Please go through some basics CMOS design rules process to know more about it.

Have you heard of postmaskECO ??

for what type of FILLER cell you are talking about ??
like i) subcon** ii) SPLIT** iii) CLIP** iv) CAP** ??

Was there any difference in nanoroute and Magma Fix-cell options in your run ??

Were you able to fix timing issues according to sign-off .

Hi Prashant,

I prefer to add std filler cell after routing if possible. It is not possilbe if there are metal blockage in the filler cell except at the power rail. Most of the std fiiller cell I worked with does not have metal blockage that will affect detailed routing.

However, it is better to add pad filler before rouitng as the router can use those space for routing if it is not fill by pad filler.

Advantage of adding filler cell later is database size. The number of std filler can be several time of the other logic cell. The overhead is not small. I can't think of disadvantage, except that you have to be sure that the filler does not have blockage that will affect routing.

Nowsaday all P&R tool can remove and add filler cells after detailed rouitng to fix timing or crosstalk. However, with nanometer process, adding of std filler cell can take awhile. So it is ready good if you can add the std filler cell just before performing full DRC.

Regards,
Eng Han

Hi Eng Han

Thanks for the explanation.

Actually i had experiece that, my design was DRC cleaned after post route optimization and when i added Filler cells, then i found some number of DRC in the design. that is why i posted this question on the portal.

Thanks & Regards,
Prashant