Thin film stress sensor suitable for different substrates

In this paper we present a device, based on amorphous silicon technology, able to perform mechanical stress measurement with both good linearity and sensitivity. A room temperature process is performed to form a very thin film of chromium silicide on the top of an amorphous silicon layer. The chromium silicide acts as the active region of the device. From an electrical point of view, the sensor can be considered as a bridge of resistances. Two contacts of the bridge are used to apply the bias current to the sensing element, while the other two, orthogonal to the previous ones, provide an output voltage proportional to the anisotropic modification of the resistivity induced by the mechanical deformation. The device is able to measure both the bending and torsion force, depending on orientation and geometries with respect to shape and location of the contacts. In this paper, results obtained on devices fabricated on several materials (glass, metal and ceramic) will be discussed.