Development of Resonant Magnetic Field Microsensors: Challenges and Future Applications

Abstract

Microelectromechanical Systems (MEMS) integrate electrical and mechanical components with feature sizes in the micrometer-scale, which can be fabricated using integrated circuit batch-processing technologies (Gad-el-Hak, 2001). The development of devices using MEMS has important advantages such as small size, light weight, low-power consumption, high sensitivity and high resolution (Herrera-May et al., 2009a). MEMS have allowed the development of several microdevices such as accelerometers (L. Li et al., 2011), gyroscopes (Che et al., 2010), micromirrors (Y. Li et al., 2011), and pressure sensors (Mian & Law, 2010). Recently, some researchers (Mohammad et al., 2010, 2011a, 2011b; Wang et al., 2011) have integrated acceleration, pressure or temperature sensors using MEMS. A potential market for MEMS will include magnetic field microsensors for applications such as automotive industry, telecommunications, medical and military instruments, and consumer electronics products (Lenz & Edelstein, 2006). The most sensitive magnetic field sensor is the Superconducting Quantum Interference Device (SQUID), which has a resolution on the order of several femptoteslas (JosephsFranks et al., 2003). It operates at low temperature based on two effects: flux quantization and Josephson effects. This sensor needs a sophisticated infrastructure that increases its size and cost, which limits its commercial applications. Hall effect sensors have a low cost, small size, and a power consumption from 100 to 200 mW. They are fabricated on standard Complementary Metal-Oxide Semiconductor (CMOS) technology and can measure either constant or varying magnetic field between temperature ranges from -100 to + 100 oC (Ripka & Tipek, 2007). Nevertheless, Hall effect sensors have a low resolution from 1 to 100 mT and require temperature compensation circuits (Popovic, 2004). Fluxgate sensors can measure static or low frequency magnetic field with a resolution of 100 pT (Ripka & Tipek, 2007). They have a size of several millimeters and a power