A Low cost micro-inertial and flow sensors based on the Direct Integration technology

The penetration of a MEMS technology into the automobile industry strongly depends on its cost. Such penetration can be accomplished by using a low cost MEMS technology that can be easily integrated with conventional silicon based microelectronics. The Direct Integration technology, presented in this paper, offers a low cost integration of displacement sensing of micro-beams with conventional microelectronics. The micro-beams, with typical cross section of 2 mm x 20 mm, are fabricated from single crystal silicon using SCREAM process, and have an in-plane degree of freedom. The sensors, made of p-n diodes and nMOS transistors, are fabricated at the beam’s support close to their root. When the beams deform stresses develop at their root that modulate the band gap energy of the silicon. This modulation affects secondary properties of the sensors at the beam’s root, that is translated into electrical signals, that are further processed by on chip ICs. The sensors and the ICs were fabricated by a conventional microfabrication facility and the mechanical elements were integrated subsequently. This integration adds only one lithography step to the fabrication steps of the IC insuring low cost integration.

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