FIB (Focused Ion Beam)

From Ref [2], Focused Ion Beam (FIB) circuit edit allows the customer to cut traces or add metal connections within a chip.

From Ref[3],

What are Spare Gates and what are the advantages of having Spare Gates in a Design
...
They can be used to do FIB(focused ion beam(it uses an ion beam to cut and expose various metal lines on a functional chip and to deposit platinum thereby reconnecting the gates into a new logic structure))
for the bug in lab before committing to a second tapeout with fix for the bug in place. FIBing is one way of
guaranteeing that the fix for the bug is going to work or not.
References
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1. http://www.eag.com/mte/focused-ion-beam-circuit-edit.html
2. http://en.wikipedia.org/wiki/Focused_ion_beam
3. CPU Design: Answers to Frequently Asked Questions