Why do we insert antenna fillers into the chip? I'm talking about cells that are left unconnected, not cells that are inserted to fix specific antenna violations that are reported by the tools (Magma, Calibre etc.)?
I don't think there are any specific Antenna Fillers placed.
Once we complete the place, route, time the design and verify the design, the left over place will be filled with dummy cells called filler cells which are not used any where.
The usage of these fillers is to maintain continuation of active regions.
Also can be replaced with new gates/cells of same type base layers for applying ECOs