A CMOS-MEMS Thermopile with an Integrated Temperature Sensing Diode for Mid-IR Thermometry

In this paper, we describe an infrared thermopile sensor comprising of single crystal silicon p+ and n+ elements, with an integrated diode temperature sensor fabricated using a commercial SOI-CMOS process followed by Deep Reactive Ion Etching (DRIE). The chip area is 1.16 mm × 1.06 mm. The integrated diode, being on the same substrate, allows a more localized measurement of the cold junction temperature compared to a conventional external thermistor. The use of single crystal silicon allows good process control and reproducibility from device-to-device in terms of both Seebeck coefficient and sensor resistance. The device has a measured responsivity of 23 V/W, detectivity of 0.75 × 108 cm√Hz/W, a 50% modulation depth of 60 Hz and shows enhanced responsivity in the 8 – 14 μm wavelength range, making it particularly suitable for thermometry applications.