Repeatability analysis of the mechanical sensitivity in MEMS gyroscopes based on piezoresistive nano-gauges

The field of Micro Electro-Mechanical Systems (MEMS) has emerged, over the last 20 years, as a technology that promises to have significant impact on daily life. The state of the art in the MEMS field is represented by capacitive read out devices. The aim of this work is to improve the repeatability of a MEMS gyroscope sensitivity, in presence of a piezoresistive read out approach instead of a capacitive one; the piezoresistive element is implemented through a nanometric gauge coupled with micormetric inertial masses. The designed gyroscopes are intended to low-power systems, they are thus suitable for consumer electronic systems and for biomedical engineering.\\ The device sensitivity depends on the process imperfections; although the electronics can in part mitigate this non-homogeneity (through a device dedicated calibration), it is desirable to gain a design that allows to gain structures as much repeatable as possible. The aim of this work is to obtain a device geometry that minimizes the sensitivity fluctuations. Another important issue is that during the lifetime of a device, some intrinsic parameters can deviate from the nominal value (e.g. due to temperature variations), compromising the whole sensitivity. In order to ensure the nominal sensitivity, the drive waveform amplitude is controlled through a motion control feedback.\\ The work is divided into two parts: a design part and an experimental one. In the design part, to face the device behavior in presence of technological imperfections Matlab models have been implemented. Innovative structure geometries have been designed and simulated using finite element analysis software, to improve the repeatability; finally the drive motion control feedback, and the overall drive system is simulated using PSpice. During the experimental part, a complete characterization setup has been developed, to investigate both the gyroscope parameters (in a clean room ambient) and its in-operation performances. The obtained results are in line with the theoretical predictions.