Keep portions of wires you might like to cut or connect in topmost metal layer.
The points you might want to connect should not be far apart.
The spot you prepare for FIB operation should not be densely populated by unrelated wires or devices.
"So in FIB it is possible to connect M6 with via and M7? Or do I have to draw M7 on top of the via?"
1. yes it can do M6+Via+M7
2. To save money (time spend in FIB process), you should always put your METAL option as top metals.
As I know, FIB means only for test.
If someone find a defect in design after manufacturing.
It can be done by chip level (with decap) or wafer level.
Is it right?
Focused Ion Beam (FIB) is a method where you can deposit new metal and/or remove/cut existing metal traces on a fabricated IC. This is done as the name implies by a Focused Ion Beam.
To be able to use the technique you first have to etch a hole in the package and afterwards you can deposit metal traces between the existing metal traces even at different layers. The main drawback is the very high resistivity in the deposited metal traces (in the order of kiloohms) so the use for RF signals is limited.
It is mainly used for debug/bugfix's of ICs.