Abstract
The study presents an ammonia microsensor integrated with a readout circuit on-a-chip fabricated using the commercial 0.18 μm complementary metal oxide semiconductor (CMOS) process. The integrated sensor chip consists of a heater, an ammonia sensor and a readout circuit. The ammonia sensor is constructed by a sensitive film and the interdigitated electrodes. The sensitive film is zirconium dioxide that is coated on the interdigitated electrodes. The heater is used to provide a working temperature to the sensitive film. A post-process is employed to remove the sacrificial layer and to coat zirconium dioxide on the sensor. When the sensitive film adsorbs or desorbs ammonia gas, the sensor produces a change in resistance. The readout circuit converts the resistance variation of the sensor into the output voltage. The experiments show that the integrated ammonia sensor has a sensitivity of 4.1 mV/ppm.
Highlights
Ammonia sensors are already widely applied in industrial and environmental monitoring.Various microsensors have been developed using microelectromechanical system (MEMS)technology, and the advantages of their microsensors are small size, high performance low cost and easy mass-production [1]
The sensitive film of the ammonia sensor was zirconium dioxide prepared by the sol-gel method [13,14] as follows: zirconium n-propoxide (Zr (OC3H7)4, 70 wt%) precursor was dissolved in ethylene glycol (C2H4(OH)2) with stirring for 3 hours until the solution was mixed uniformly
An ammonia sensor integrated with a readout circuit, proposed by Yang et al [15], was manufactured by the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and a post-process
Summary
Ammonia sensors are already widely applied in industrial and environmental monitoring. An ammonia sensor, proposed by Patois et al [5], was manufactured using silicon microtechnology, and the sensitive film of polypyrrole was electrochemically deposited on platinum microelectrodes. The ammonia sensors, presented by Lee et al [2], Yoon et al [3], Carquigny et al [4], Patois et al [5], Triantafyllopoulou et al [6] and Llobet et al [7], were not integrated with circuitry on-a-chip. The CMOS-MEMS technique uses the commercial CMOS process to develop MEMS devices [8,9] Microdevices fabricated by this technique can be integrated with circuits as a system on a chip (SOC). An ammonia sensor with a readout circuit on chip is developed utilizing the CMOS-MEMS technique. The post-process consists of etching the sacrificial oxide layer and depositing the sensitive film
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