this issue arrive during the foundry process.
the metal layer are charge by the process, and when the final connection is done, this electical charge discharge in the gate which could not be enought strong, and the gate "burn".
During the routing phase, this will solved.
When a metal layer is being etched during process, charge particles are deposited on the metal due to friction. More the length of the net more is the charge accumulated.
Suppose in my design I has a long running net connected to std cell gate then the charge particles deposited on a net will be more and this charge can develop a voltage more than the vth of std cell, resulting in the damage of the gate.
When ever the antenna effect is identified in the design. Following ways can be used to fix them.
1. Long running nets have to be broken.
2. Placing a reverse-biased diode