FILL factor

Hi,
When I every time send GDSII file to the foundry, I need to check the
pattern density. Every layer must take a certain percentage in the chip.
For example, the PC layer must be bigger than 10% but be less than 30%.
I don't know very clearly why I need to do it every time. Does anyone know
it very clearly?

Thank you very much!


sincerely

 

you need to do it every time because you're submitting every time!
Normally, you'd have check this before starting any layout. So, if
it is required you can implement it when you're doing your cells and
by the end of you're finish you can correct for the small percentage
error.(make sure that you're turning the appropriate drc switches)
The other way around is if you learn that is required afterwards,
so you can go ahead and fill empty spaces and verify thru drc.
the filling is to solve the planarization problem.
Some times the foundry may fill it for you and thus does not require
you to do it. But it is wise to do yourself so you know exactly what
is on your chip.
hth