  Current density distributions in active integrated circuits (ICs) result in
patterns of magnetic fields that contain structural and functional information
about the IC. Magnetic fields pass through standard materials used by the
semiconductor industry and provide a powerful means to fingerprint IC activity
for security and failure analysis applications. Here, we demonstrate high
spatial resolution, wide field-of-view, vector magnetic field imaging of static
(DC) magnetic field emanations from an IC in different active states using a
Quantum Diamond Microscope (QDM). The QDM employs a dense layer of fluorescent
nitrogen-vacancy (NV) quantum defects near the surface of a transparent diamond
substrate placed on the IC to image magnetic fields. We show that QDM imaging
achieves simultaneous $\sim10$ $\mu$m resolution of all three vector magnetic
field components over the 3.7 mm $\times$ 3.7 mm field-of-view of the diamond.
We study activity arising from spatially-dependent current flow in both intact
and decapsulated field-programmable gate arrays (FPGAs); and find that QDM
images can determine pre-programmed IC active states with high fidelity using
machine-learning classification methods.
