Micro-infrared thermometry for characterizing microscale heating devices

Abstract

Infrared thermometry is a non-destructive and non-contact temperature measurement technique that allows for real-time, full-field imaging. However, the limited spatial resolution of infrared detectors and the scarcity of mid- and far-infrared lenses have hindered its use in microscale applications. To address this, we introduce an infrared microscope that employs a bolometer-type infrared detector and a reflective objective lens, enabling high-resolution temperature measurements of microscale heating devices. The reflective objective lens used in the microscope introduces intensity reduction due to magnification and undesirable background radiation caused by its cavity effect. To mitigate these issues, we utilized a custom-built micro-blackbody for calibrating intensity reduction and eliminating background radiation. The proposed micro-infrared thermometry setup was characterized by MDTD and MRTD measurements, as well as an MTF curve with a pixel resolution of 6.7μm/pixel and a spatial resolution of 12.5μm. To evaluate the effectiveness of the micro-infrared thermometry, we fabricated a suspended microscale heating device that can exhibit a clear temperature distribution. The temperature distribution obtained using both the differential conversion and Fast Fourier-Transform methods to eliminate background radiation agreed well, with a maximum difference of 3.2°C and 4.1°C in the range from room temperature to 77°C and 145°C, respectively. Furthermore, we compared our experimental results with COMSOL simulations and found them to be reasonably consistent, with a maximum difference of 6.1°C and 7.0°C in the range from room temperature to 77°C and 145°C, respectively.