High-Spatial-Resolution Near-Infrared Thermography Using an Uncooled Silicon-Based Camera

Abstract

The demand for noncontact temperature measurements is growing as the microelectronic features to be probed become progressively smaller. However, traditional thermal imaging with infrared cameras is fundamentally constrained by the micron-long wavelength of thermal emission. In this study, we explore a cost-effective, high-spatial-resolution thermography technique utilizing an uncooled silicon CMOS camera with an optical microscope setup. By detecting the integrated near-infrared (NIR, 700–1100 nm) thermal emission from Joule-heated metallic microstructures, our method successfully bypasses the traditional microbolometer’s diffraction limit and spatial resolution constraints. To ensure accurate temperature estimation, the camera is calibrated by leveraging the temperature-dependent Raman peak shift of hexagonal boron nitride flakes. Our optical microscope setup is in an oversampling condition, allowing us to exploit digital binning to achieve significant noise reduction and to directly visualize and map thermal emission at temperatures as low as 413 K for our titanium sample, which has an emissivity of around 0.4 in the NIR. This method provides a robust, highly capable tool for diagnosing localized thermal bottlenecks and mapping heat diffusion in high-density microelectronics.