During the IC fabrication process, what is the primary cause of the 'antenna effect', and what is a common physical design solution to mitigate it?
The antenna effect (or Plasma Induced Gate Oxide Damage) occurs during plasma etching. A long metal trace connected to a transistor gate acts like an antenna, collecting charge. This charge can build up to a voltage high enough to damage the thin gate oxide. Common fixes include inserting a reverse-biased diode (antenna diode) near the gate to provide a safe discharge path, or 'jumpering' the long lower-level metal trace to a higher metal layer, which is etched later in the process, thus reducing the effective antenna ratio.
