Toward an Accurate IR Remote Sensing of Body Temperature Radiometer Based on a Novel IR Sensing System Dubbed Digital TMOS

Abstract

A novel uncooled thermal sensor based on a suspended transistor, fabricated in standard CMOS-SOI process, and released by dry etching, dubbed Digital TMOS, has been developed. Using the transistor as the sensing element has advantages in terms of internal gain, low power, low-cost technology, and high temperature sensitivity. A two channel radiometer, based on the new nano-metric CMOS-SOI-NEMS Technology, enables remote temperature sensing as well as emissivity sensing of the forehead and body temperatures of people, with high accuracy and high resolution. Body temperature is an indicator of human physiological activity and health, especially in pediatrics, surgery, and general emergency departments. This was already recognized in past pandemics such as SARS, EBOLA, and Chicken Flu. Nowadays, with the spread of COVID-19, forehead temperature measurements are used widely to screen people for the illness. Measuring the temperature of the forehead using remote sensing is safe and convenient and there are a large number of available commercial instruments, but studies show that the measurements are not accurate. The surface emissivity of an object has the most significant effect on the measured temperature by IR remote sensing. This work describes the achievements towards high–performance, low-cost, low power, mobile radiometry, to rapidly screen for fever to identify victims of the coronavirus (COVID-19). The main two aspects of the innovation of this study are the use of the new thermal sensor for measurements and the extensive modeling of this sensor.

Novel Grey Body for Accurate Radiometric Measurements

“…Figure 3 exhibits the measured data of the blackbody temperature and emissivity. The two-channel radiometer based on the Digital TMOS [11] has been reported in Micromachines, 2022, Toward an Accurate IR Remote Sensing of Body Temperature Radiometer Based on a Novel IR Sensing System Dubbed Digital TMOS [12]. The TMOS is a micromachined n-MOS CMOS transistor operating at subthreshold and performing as a thermal IR uncooled sensor.…”

Reference Temperature Sensor for TMOS-Based Thermal Detectors

“…T HERMAL detectors, including bolometers, pyrometers, thermopiles and the recently developed TMOS, are employed in a wide range of applications: contactless absolute temperature measurements, presence and movement detection, gas analysis, climate control systems, space and military applications, security systems, medical devices, temperature monitoring in manufacturing processes, appliances and consumer products (microwave ovens, clothes driers, laser printers) [1]. Thermopiles [2]- [8] and the TMOS sensor [9]- [13], [15], in particular, have proven to be the most apt thermal detectors as they are compatible with standard CMOS processes and, therefore, enable large volume low cost production. Thermopiles operation relies on the Seebeck effect [1], [2], [7], while the TMOS sensor, consisting of a thermally isolated equivalent transistor able to absorb thermal radiation, exploits how the transistor I-V characteristics change depending on the temperature variation caused by the absorbed thermal radiation [1], [10]- [12].…”

“…Furthermore, the reference sensor does not measure the blind TMOS temperature as it is not located on the TMOS chip, but on its readout circuit chip. Indeed the TMOS sensor is sealed under vacuum employing wafer level packaging while its bias and readout circuit are integrated on a separate chip, which is subsequently bonded on the same package as the TMOS sensor [15]. This paper proposes a solution to measure the reference temperature accurately and directly, with the aim of enabling the use of TMOS sensors, now limited on the market to presence and motion detection solutions, to absolute temperature measurements applications, and in particular human body temperature measurements.…”