Concurrent enhancement of thermopile responsivity and response speed via thermocouple number and multi-dielectric layer engineering

Abstract

Fast response and high-sensitivity are both required for thermopiles used in real-time non-contact temperature monitoring. However, as a thermal detector, the response speed of a thermopile is often subject to a trade-off with its sensitivity. Existing solutions, such as combining small sensing structures, high-infrared-absorption materials, and high-Seebeck-coefficient thermoelectric materials, have challenges in complex design and CMOS compatibility. Here, we report a new design strategy that concurrently enhances responsivity and response speed by engineering the number of thermocouples and SiO2/SiNx multi-dielectric layers, with little added complexity or cost. The fabricated sensor with 90 thermocouple pairs and two pairs of SiO2/SiNx layers achieves a response time of 27.30 ms, and a responsivity of 71.76 V/W, which is 9.12% and 119.58% enhancement, respectively, compared to the reference sensor with 45 thermocouple pairs and a single pair of SiO2/SiNx layers (30.05 ms, 32.68 V/W). Simulation and experimental results reveal that the increased number of thermocouples enhances both thermal conductance and cumulative voltage signal, while the two-pair multi-dielectric layers improve infrared absorption. This work demonstrates that engineering both thermocouple number and multi-dielectric layers is a simple, CMOS-compatible and cost-effective way to concurrently enhance response speed and sensitivity. This design strategy is a promising route for developing high-performance photo-thermo-electric devices.