Single wafer miniature Hall-effect keyboard

A design is proposed for a miniature Hall-effect keyboard for use in hand-held calculators. The keyboard includes a set of MOSFETs as the Hall effect sensors and all the necessary electronic components for keyboard control and communication on a single silicon substrate. Because of the elimination of wire connections to each key-cap and the use of MOSFET circuitry for key sensing, the implementation is expected to lead to high reliability and low power consumption. Some design aspects, including mask layout, and process steps are described