Optimization of MEMS-Based Capacitive Sensor with High-k Dielectric for Detection of Heavy Metal Ions

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Nowadays, all the countries worldwide facing lots of environmental issues out of which Heavy Metal Ions (HMIs) contamination is extremely harmful and hazardous to human health. Many countries were facing enormous challenges to solve this HMIs problem. Air and Water pollution due to HMIs is a global issue and required to solve as early as possible to maintain today’s air and water quality demands. A portable device made using MEMS-based sensors technology recommended to detect the multiple analytes simultaneously for environmental monitoring applications. Accordingly, our main objective is to optimize and design a capacitive MEMS-Based sensor platform utilized for sensing the low concentration of HMIs. As we know, a proposed capacitive sensor is designed using MEMS-based technology, which ultimately produces the capacitance in the femtofarads (fF) range. It is tough and costly to measure this fF range of capacitance. An individual capacitance to digital converter (CDC) circuit is required to measure this capacitance produced by MEMS-based sensors. Hence, we have used the HfO2 as High-k dielectric layer to increase the sensor capacitance in picofarads (pF) range to use the market available CDC circuit AD7150. This mixed dielectric approach is beneficial to solve the problem of measurement in capacitive sensors for the low-cost application using the market available embedded systems. In this work, we try to optimize the microcantilever-based capacitive MEMS sensor with a different thickness of HfO2 as a High-k material using COMSOL Multiphysics 5.3 software. The FEA analysis for an optimized capacitive sensor with HfO2 as a High-k dielectric shows the maximum capacitance variation 3.5 fF compared to 0.3 fF without High-k for HMIs mass between 1 and 1000 µg.