ABSTRACT
An accelerometer is a spring mass system in a box, plus a sensor to measure the displacement of the mass, and the box will be the silicon chip. The measurement of the displacement is critical, since it determines the resolution of the sensor. As a sacrificial layer, silicon oxide is the ideal partner for polysilicon. Both layers are made by high temperature oven processes, and selective etching is easily possible using hydrofluoric acid HF, which will dissolve oxide but not attack the silicon. Sensor fusion systems estimate a value (inclination, orientation, etc.) and correct the estimation continuously by comparing it to the input from two (or more) sensors working with different physical principles. In this way, they can combine the advantages of both measurement principles.
