Quantum Diamond Microscope II – Imaging of electrical currents
The large-area magnetic imaging technique of the QDM (see page 1)opens up new applications, one of which we would like to present here.
Every current generates a magnetic field and vice versa. It therefore makes sense to use QDM for imaging currents in electrical components. The distribution of current densities in active integrated circuits (ICs) contains information about the structure and function of the circuit. The magnetic fields penetrate common materials used in the semiconductor industry and thus offer an effective way of analyzing the operating behavior of an IC. The magnetic fields vary depending on the operating state. Magnetic imaging can provide information about the structure and behavior of the circuit, which can be used for testing and troubleshooting. QDM can be used to map the magnetic fields of ICs under operating conditions. Edlyn V. Levine (Havard University), together with Amir Yacoby, Marko Loncar and other colleagues, has shown how information about the function and state of the IC can be derived from the field distribution [1]. Figure 1 shows the field distribution in the X, Y and Z directions for two different areas of a field programmable gate array (FPGA). Each area contains a cluster of 200 ring oscillators (ROs). The currents flowing through the vertical traces on the right-hand side of the image are clearly visible. In Figure 2, the measured magnetic field is plotted over an image of the circuit. The group has used machine learning techniques to classify operating states of both decapsulated and intact FPGAs based on the correlation of magnetic field patterns. This makes it possible to recognize the activity of individual areas and whether the operation corresponds to the norm.
[1] Matthew J. Turner, Nicholas Langellier, Rachel Bainbridge, Dan Walters, Srujan Meesala, Thomas M. Babinec, Pauli Kehayias, Amir Yacoby, Evelyn Hu,Marko Loncar, Ronald L. Walsworth,and Edlyn V. Levine, Magnetic Field Fingerprinting of Integrated-Circuit Activity with a Quantum Diamond Microscope, Phys. Rev. Applied 14, 014097 - Published July 31, 2020