Single Wafer Miniature Hall-Effect Keyboard

A new design of a miniature Hall-effect keyboard for use in hand-held calculators is proposed. The keyboard includes a set of MOSFET's as the Hall effect sensors and all the necessary electronic components for keyboard control and communication on a single silicon substrate. Due to 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 to low power consumption. Some design aspects including mask layout and process steps are described.