Magnetic Field Fingerprinting of Integrated-Circuit Activity with a Quantum Diamond Microscope

Current density distributions in active integrated circuits result in patterns of magnetic fields that contain structural and functional information about the integrated circuit. Magnetic fields pass through standard materials used by the semiconductor industry and provide a powerful means to fingerprint integrated-circuit activity for security and failure analysis applications. Here, we demonstrate high spatial resolution, wide field-of-view, vector magnetic field imaging of static magnetic field emanations from an integrated circuit in different active states using a quantum diamond microscope (QDM). The QDM employs a dense layer of fluorescent nitrogen-vacancy (N-$V$) quantum defects near the surface of a transparent diamond substrate placed on the integrated circuit to image magnetic fields. We show that QDM imaging achieves a resolution of approximately $10\phantom{\rule{0.1em}{0ex}}\ensuremath{\mu}\mathrm{m}$ simultaneously for all three vector magnetic field components over the $3.7\ifmmode\times\else\texttimes\fi{}3.7\phantom{\rule{0.2em}{0ex}}{\mathrm{mm}}^{2}$ field of view of the diamond. We study activity arising from spatially dependent current flow in both intact and decapsulated field-programmable gate arrays, and find that QDM images can determine preprogrammed integrated-circuit active states with high fidelity using machine learning classification methods.