A silicon bulk micromachined capacitive force feedback accelerometer

The object of this work was to make a capacitive accelerometer using the same silicon technology as a resonant pressure sensor. The target was for a full scale range of ±2g, for which there are a number of applications such as short term inertial navigation and heading sensors. The sensor consists of three Si chips bonded together by layers of insulating glass. The centre chip has a moving mass supported by flexures formed using a boron etch stop. The outer two chips form electrodes which are spaced about 10 μm away from the moving mass. The movement of the mass can be sensed by the differential change in capacitance as the mass moves nearer one electrode and away from the other