Sensing Electric Currents in an a-IGZO TFT-Based Circuit Using a Quantum Diamond Microscope

Abstract: The Quantum Diamond Microscope (QDM) is an emerging magnetic imaging tool enabling noninvasive characterization of electronic circuits through spatially mapping current densities. In this work, we demonstrate wafer-level current sensing of a current mirror circuit composed of 16 amorphous-indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). a-IGZO TFTs are promising for flexible electronics due to their high performance. Using QDM, we obtain two-dimensional (2D) magnetic field images produced by DC currents, from which accurate current density maps are extracted. Notably, QDM measurements agree well with conventional electrical probing measurements, and enable current sensing in internal circuit paths inaccessible via conventional methods. Our results highlight QDM's capability as a noninvasive diagnostic tool for the characterization of emerging semiconductor technologies, especially oxide-based TFTs. This approach provides essential insights to fabrication engineers, with potential to improve yield and reliability in flexible electronics manufacturing.