Abstract: In this paper, a methodology to simulate the electric behavior of spiral inductances is presented and discussed. All the methodology is built with the Comsol software used with the Matlab scripting interface and then allows performing fully parameterized simulations. The program architecture is explained and is used to simulate two applications. The first calculates the voltage induced by an external AC magnetic field. The second is to detect the presence of moving metallic particles of micrometric dimensions; the program thus extracts the varying inductances values. The final goal of this approach is to manufacture sensors in MEMS technologies and co-integrate them with CMOS circuits. Keywords: Inductance, FEM simulation, magnetic sensor, spiral-shaped. 1. Introduction Magnetic sensors are needed in a lot of applications but because of the increasing complexity and consumption of systems, they have to be miniaturized to reach confined areas and work at very low power. The methodology presented here is used to simulate the electric response of a square-shaped spiral MEMS inductor in the case of two applications, magnetic field measurement and metallic particle detection. The future purpose of this work is to manufacture inductance in MEMS technologies and to integrate them with CMOS circuit to limit the impact of wire connections; it thus becomes easier to extract the information provided by the sensor. Several works have been achieved in the MEMS inductor fabrication like [3], [4] and [5]. The methodology starts from the existing library Comsol model of the square inductor [1]. We largely extend this approach and explain it with a more electronical than mathematical point of view on the parameter values. This paper is divided in three sections. The first explains which equation model is used to solve the problem and presents the system geometry. The second part develops the programming structure and describes the strategy used to build a robust finite element structure. The last section shows the simulation results by extraction of the electric response. The inductance and resistance values are calculated before showing the magnetic field and particle detection results. 2. Model description 2.1 Equation model The electromagnetic module is used for all the simulations; it consists in the general expression of the electric and magnetic potentials (expression 1 and 2). The system is defined by four variables to solve, one for the electric potential and three for the magnetic potential. All symbols are described in Table 1.                      (1)                                (2) Table 1: equation parameter description Parameter description Symbol Units Type Electric potential V [V] / Magnetic potential A [T.m] / Angular frequency ω [rad.s -1 ] variable Electric conductivity σ S.m -1 variable Relative permittivity ε0 [-] constant Absolute permittivity εr [F.m -1 ] constant Relative permeability μ0 [-] constant Absolute permeability μr [H.m -1 ] constant 2.2 Inductance geometry The geometry is built with the Matlab scripting interface and is generated automatically according to the input parameters. Fig. 1 shows an example of the geometry built with the input parameters described in Table 2. The outer domain is divided into two parts, the substrate (lower box) and the air (upper box) which are large enough to avoid boundary effects. All the simulations are based on the resulting magnetic field generated in the system. A Methodology for the Simulation of MEMS Spiral Inductances used as Magnetic Sensors Sylvain Druart, Denis Flandre, and Laurent A. Francis Université catholique de Louvain – ICTEAM Institute B-1348 Louvain-la-Neuve, Belgium {Sylvain.Druart, Denis.Flandre, Laurent.Francis}@uclouvain.be Excerpt from the Proceedings of the COMSOL Conference 2010 Paris