Micromachined Silicon Transducers for Measuring Force, Pressure, and Motion

Integrated-circuit technology has provided the capability of defining very precise patterns on a silicon surface. When these patterns are used with advanced chemical etching techniques, well defined, very small structures can be formed from a silicon wafer, thereby suggesting a low-cost method of batch fabricating highly uniform, highly repeatable physical shapes. The combination of IC photolithography plus controlled etching of silicon has been labelled "micromachining," because of the inherent precision it provides. Certain kinds of silicon are highly piezoresistive, in that the resistivity changes very significantly with applied stress. Piezoresistors formed in such silicon enable us to convert mechanically induced stress into an electrical signal. Including piezoresistors into appropriate micromachined silicon shapes thus yields transducers for measuring such physical quantities as acceleration, pressure, and force, as will be described in this paper.