Contents - Akademi Sains Malaysia

ASM Sci. J., 7(1), 27–36Investigations on Physical Characteristics ofThree-dimensional Coil Structure forMEMS MagnetometerN. Sulaiman 1 * and B. Y. Majlis 1Measurement of low magnetic field has played an important role in many electronics applications such asnavigation, military, non-destructive test, traffic detection as well as medical diagnosis and treatment. Thepresence of magnetic field, particularly its strength and direction, can be measured using magnetometer. Thereare many types of magnetometers being investigated through the years and one of the prominent types isfluxgate magnetometer. The main components of fluxgate magnetometer consisting of driving coils, sensingcoils and magnetic core are developed by MEMS silicon processing technology. In this paper, an investigationon physical characteristics of the three-dimensional coil structure for a micro-scaled fluxgate magnetometeris presented. The physical characteristics such as width of the coil, distance between successive coils, and gapbetween the top and bottom coils which would influence the magnetic energy in magnetometer is discussed.In this work, finite-element method simulations to investigate the physical characteristics of the sensing coilswere carried out, where the parameter of interest is the coils’ inductance as well as the magnetic flux density.Based on the simulation results, the varying of physical characteristics of the coils had its effects particularlyin coil inductance, magnetic flux density, and magnetic energy. It could also be seen that the simulated resultsagreed with the theoretical aspects of magnetism in a coil. From the investigations, suitable coil dimensionswere proposed.Key words: Coil; magnetic flux density; energy; MEMS device; fluxgate magnetometer; simulationMagnetometer is a device mainly used to measure thestrength and direction of magnetic fields. It has a widerange of application which includes space exploration,navigations, geology studies, geophysics analysis andmedical diagnosis. Many types of magnetometer withdifferent principle of operation have been invented.Fluxgate is a type of magnetometer in which the principleof operation is based on second harmonics detection ofvoltage induced in sensing coil (Ripka 2003).In recent years, the miniaturization of fluxgatemagnetometer has come into interest due to the advantageof its smaller size, less power utilization and lowfabrication costs. Miniaturized fluxgate with different coildesigns have been reported that includes spiral single layerplanar (Yunas et al. 2010), multilayer/double coil (Atta2004; Ripka et al. 2001), double axis type (Baschirottoet al. 2007), toroidal type (Dezuari et al. 1999), and threedimensionalsolenoid type (Liakopoulos et al. 1999;Wanget al. 2006; Lei et al. 2009).The performance of fluxgate is closely related to the coildesign type. This is due to the fact that different coil designproduces different inductances, and magnetic flux densitywhich among others are the parameters that influence theperformance of the device.In this paper, we investigated the physical characteristicsof three-dimensional coils and its correlation withmagnetic energy. The investigation was done by meansof FEM simulation. The parameters of interest in thesimulation were coil inductance and magnetic flux density.Information from the simulation results could aid in propergeometry design of three-dimensional coils.THREE-DIMENSIONAL COILFluxgate coils consist of a driving coil and a sensing coil.In order to achieve three-dimensional structure, the coilsare designed in such a way that it consists of three parts1 1Institute of Microengineering an Nanoelectronics, University Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia.* Corresponding author (e-mail: nad0903@gmail.com; burhan@vlsi.eng.ukm.my)27