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This work is focused on the developing of silicon resonant microcantilevers for the measurement of the absolute pressure. The microcantilevers have been fabricated through two different versions of bulk micromachining processes. The first release is based on a 2-masks mixed front and back-side bulk micromachining process. Vertical resonant actuation and resonance detection are both externally implemented, respectively through an adequately driven piezoelectric actuator and an optical lever exploting a PSD photodetector. The variation in resonance response of microcantilevers was investigated as a function of pressure (0,1 to 100000 Pa), both in terms of resonance frequency and quality factor. A theoretical description of the resonating microstructure is given according to different molecular and viscous regimes. Also a brief discussion on the different quality factors contributions is presented. Theoretical and experimental data show a very satisfying agreement. The microstructure behaviour demonstrates the feasibility of an absolute pressure sensor working over a six decades range. The second release is based on a 4-masks front-side bulk micromachining process. Lateral resonating microcantilevers are obtained through a high aspect ratio Deep Reactive Ion Etching. A significative upgrade is represented by the integration of the actuator and the sensing directly on chip providing a more compact and potentially interesting solution for industrial vacuum applications. Actuation is performed exploiting an electrostatic modulated force, while detection relies on a capacitive readout scheme, so all the sensing chain (actuation, sensor structure and detection) is based on standard MEMS technologies and electronics for a truly integrated microsystem prototype. First experimental evidences show encouraging results towards the target to replicate the outstanding results obtained with the first version. |