metal density is just a check to make sure there is uniform density across the chip for manufacturing reasons.
In FE you can add metal for each layer. First you setup some parameters like fill density, fill spacing between active layers etc. Then you run addmetalfill command. This should be the last step in the flow because modifying it is not easy.
generally we try to meet around 30% coverage for each layer. Since FE does not account for analog blocks, we will go with even less than 30% in FE.
-pOriginally posted in cdnusers.org by pjayasekharan