What are filler cells？

Filler cellsare just cells which do nothing..

If any changes are required in the layout after the whole layout process is complete(say u encounter a hardware bug), one can remove the filler cells and place actual logic instead of that.

Typical use is when ECOs occur in the design.

FIller Cell are empty Cells with only Power and Ground Rails. After Place and Route there will be enpty areas left in the row and hence the power will not reach all the cells due this discontinuity. After adding filler cells this discontinuity will go away. Also few people make use of filler cell for increasing the metal density and poly density by using the empty space in filler Cell.

filler cells also have two types : with cap or not. please add the cap first

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E文交流综合征~ 哈哈，

thx for focus, hei hei...

it is very hard question