4. Applications for micromachined structures

4.1 Pressure sensors

Many of these sensors consist of a silicon membrane a few tens of micrometers in size, with lateral dimensions of 1 to 5 mm. The pressure difference between the two faces is detected, either by measuring stresses at embedding with diffused piezoresistive gauges, or by evaluating deformation using a capacitive structure. Competing principles exploit non-linear effects inducing a variation in the resonance frequency of the diaphragm or an associated structure (vibrating bridge).

Several processes can be used to produce the membrane:

• anisotropic etching of the back of the substrate and control of membrane thickness based on etching speed and time. On the front face, any trenches of controlled depth...