Procedia Engineering 00 (2009) 000–000 Procedia Engineering www.elsevier.com/locate/procedia Proc. Eurosensors XXIV, September 5-8, 2010, Linz, Austria Ultra Low Power flow-to-frequency SOI MEMS transducer N. André, B. Rue, D. Van Vynckt, L. A. Francis, D. Flandre and J.-P. Raskin Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Université catholique de Louvain, Place du Levant, 3, Louvain-la-Neuve B-1348, Belgium Abstract Silicon-on-Insulator (SOI) technology, with unique properties such as harsh environment resistance and lower power consumption [1], is presented here as a platform for CMOS and MEMS co-integration. An original CMOS-compatible process has been developed for the design and the co-fabrication of out-of-plane (3D) movable cantilevers and ring oscillators (RO) circuits on the same chip. The measured transducer, by deflection of the out-of-plane MEMS component, shows until 10% variation of the frequency under different flow rates. © 2009 Published by Elsevier Ltd. Keywords: CMOS; Thin Films; Ultra Low Power 1. Introduction Co-integration of CMOS circuits and MEMS within a single package or die is the objective of many research groups to improve sensors performance or integration level as well as the cost. To interface extremely small capacitance variations (several hundred femtofarads depending on the out-of-plane beams deflection) from a capacitive transducer, co-integration of the MEMS transducer with an integrated read-out IC is mandatory to minimize parasitic elements and thus provide high sensitivity. A SoC (System-on-Chip) technology, building the sensor and the circuit on the same substrate using thin film SOI technology wafers and traditional CMOS- compatible layers, following by a post-process release as in [2]-[3], is presented in this work. 2. Fabrication Classically with micro-electro-mechanical system (MEMS), microcantilevers are widely used in atomic force microscopy (AFM), mass sensing, contact sensing and force measurements. A change in surface tension or surface stress, due to interfacial interactions between the surface and the environment or intermolecular interactions on the surface, is detected electrically whether it is by resistive or capacitive measurements. In this section, we introduce a method to fabricate three-dimensional cantilevers using both microfabrication techniques and mechanical stress in multilayered thin films and to co-integrate this mechanical sensing component and the complementary metal-oxide semi-conductor (CMOS) circuit on a same silicon chip. The term three- dimensional (or 3-D) is used here to design a structure presenting a non-flattened geometry, i.e. an out-of-plane