Sensors are devices that provide an interface between electronic equipments and the physical world; they help electronics to "see", "hear", "smell", "taste" and "touch" In their interface with the real world, sensors, typically, convert non electrical physical or chemical quantities into electric signals (MEMS).To built MicroElectroMechanical System Silicon plays, as material, a dominant role. Its elastic and mechanical properties are comparable to those of steel and it is not subjected to mechanical hysteresis. In this work using a modified epitaxial technique, we were able to obtain the first prototypes of accelerometers and gyroscopes fully working. Using this technique developed in the Cornaredo R&D labs of SGS-Thomson, it is possible to grow, selectively and at the same time, a monocrystalline EPI layer for the active structures and a polycrystalline one for MEMS. At the end of the process, using "trench" like etches, it is possible to create the accesses for the sacrificial layer removal obtaining the mobile masses anchored to the bulk with elastic silicon suspensions for an acceleration sensors or gyroscopes.Such kind of technique allows to realise the sensing element in the same silicon chip as the control circuitry.In contrast to conventional surface micromachining, where structures present some drawbacks, caused by the limited thickness of the constructional layer (2μm), these epipoly microelectromechanical devices are countersunk in the epitaxial layer, yielding a highly planar structure, and are rather stiff in the vertical direction due to their large epipoly thickness (10μm). This lowers the probability of stiction of these devices to the underlying substrate. In addition the thicker layer leads to a relatively large value of both proof mass and readout capacitance (1pF). The whole characterisation is running; from the first data the lack of hysteresis is confirmed.
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