Review—System-on-Chip SMO Gas Sensor Integration in Advanced CMOS Technology

Abstract

The growing demand for the integration of functionalities on a single device is peaking with the rise of IoT. We are near to having multiple sensors in portable and wearable technologies, made possible through integration of sensor fabrication with mature CMOS manufacturing. In this paper we address semiconductor metal oxide sensors, which have the potential to become a universal sensor since they can be used in many emerging applications. This review concentrates on the gas sensing capabilities of the sensor and summarizes achievements in modeling relevant materials and processes for these emerging devices. Recent advances in sensor fabrication and the modeling thereof are further discussed, followed by a description of the essential electro-thermal-mechanical analyses, employed to estimate the devices' mechanical reliability. We further address advances made in understanding the sensing layer, which can be modeled similar to a transistor, where instead of a gate contact, the ionosorped gas ions create a surface potential, changing the film's conduction. Due to the intricate nature of the porous sensing films and the reception-transduction mechanism, many added complexities must be addressed. The importance of a thorough understanding of the electro-thermal-mechanical problem and how it links to the operation of the sensing film is thereby highlighted.

Mass Sensors Based on Capacitive and Piezoelectric Micromachined Ultrasonic Transducers—CMUT and PMUT

“…The etching is done up to the SOI wafer and then the insulation layer, formed at the beginning, is removed, as illustrated in Figure 12e,f. The backside etching technique has been reported to be used for backside cavities in PMUT-based sensor fabrication ranging over hundreds of microns [49,50].…”

Thermo-Electro-Mechanical Simulation of Semiconductor Metal Oxide Gas Sensors

“…There are many different gas sensing principles under investigation today and some have already found success in industry and research. These include semiconducting materials, optical devices, thermal conductivity sensors, infrared (IR) detectors, quarz microbalance sensors, catalytic detectors, dielectric detectors, electro-chemical sensors, and electrolyte based sensors [44,45,46,47]. While all types have their advantages and disadvantages, the semiconducting metal oxide gas sensor appears to be the most appropriate choice for miniaturization, low power conduction, and thereby portable applications.…”

“…The primary classification for gas sensor devices includes those whose sensing mechanism is based on a change in the electric properties of a film and those whose sensing mechanism is based on a variation of another material property, when a target gas is found in the ambient [48]. Table 1 stems from a collection of recent reviews from Korotcenkov [45], the updated discussion by Dey [46], as well as the updates and additions of photoionization and piezoelectric devices from Filipovic and Lahlalia [47].…”

“…Furthermore, the temperature provided has a large impact on the sensing response, while knowing the exact microheater behavior is not always possible, especially since the properties of the microheater materials change with time under operation. These changes can be brought up by the induced thermal stresses, thermo-migration, or electro-migration [47]. The SMO’s selectivity is another concern.…”

Solución Analítica de la Distribución de Temperaturas en un Medio Homogéneo Debido a un Cable Eléctrico con Forma de Onda Rectangular

“…Utilizando la solución analítica obtenida, se presenta una ecuación simple que permite calcular la conductividad térmica efectiva de un cuerpo a partir de los datos experimentales de temperatura y posición. Dado que la situación física es similar a la encontrada en calentadores eléctricos [22,23], dispositivos termo-ópticos y dispositivos microfluídicos termo-regulados [24][25][26], los resultados de esta investigación pueden ser usados en el diseño de estos aparatos y ofrecen la posibilidad de establecer procedimientos experimentales que faciliten la determinación de la conductividad térmica efectiva de un material.…”