A MEMS-CMOS Microsystem for Contact-Less Temperature Measurements

This paper presents a microsystem suitable for contact-less human body temperature measurements, as well as for presence, motion and proximity detection. It consists of a 130-nm CMOS-SOI MEMS (Micro-Electro Mechanical System) thermal sensor, referred to as “TMOS”, and its 130-nm CMOS interface circuit. The TMOS, based on a micromachined transistor, being an active device, features advantages in terms of internal gain: with optimal biasing, indeed, the TMOS achieves 274- $\mu \text{V}/^\circ \text{C}$ input-referred sensitivity at 3-cm distance and 50.33° field-of-view (FOV), outperforming thermopile detectors. The sensor and the interface circuit, featuring a chopper-stabilized-based analog readout with a 12-bit SAR ADC (Successive Approximation Register Analog-to-Digital Converter), were mounted in the same package and extensively measured: the microsystem achieves repeatability and ±0.17°C precision, thus satisfying the requirements for contact-less human body temperature measurements; furthermore, its performance as presence, motion and proximity detector was also verified.