Double Vias and Antenna Violations

A Search and Repair run done later to resolve DRC may cause antenna violations.
Turning on antenna checking rolls double vias back to single vias, which reduces antenna violations.

KEY Double vias themselves are usually safe; later DRC repair can cause antennas, and antenna checking rolls them back.

Filler Cell Insertion

For good yield, the chip density needs to be uniform, but some placement sites on certain rows remain empty.
The tool accepts two lists of filler cells - with metal and without metal.
Cells without metal are inserted without DRC checking, so you must provide cells that have no metal.
Cells with metal are inserted only where they do not cause a DRC violation.
Filler cells are inserted in the specified order, and inserting from larger to smaller is recommended.
By default, filler insertion honours hard and soft placement blockages.

KEY Filler cells fill empty placement sites to keep density uniform for yield, honouring blockages and DRC.

Non-uniform metal density causes manufacturing problems, especially during chemical mechanical polishing (CMP).
Extraction in the FILL view does not account for metal fill.
Extraction in the CELL view does not correctly account for fill.
Timing analysis does not consider metal fill.

KEY Metal fill keeps metal density uniform for CMP, but extraction and timing do not fully account for it.