Interactive two-dimensional design of barrier-controlled MOS transistors

An interactive program has been developed for the graphic generation and the solution of two-dimensional impurity, carrier, potential, and field distributions in small-geometry MOS transistor configurations. Emphasis is placed on conversational operation and three-dimensional display on a graphics terminal with a generation rate, for any self-consistent two-dimensional solution, of less than few minutes for each computation and drawing. Although this limited the approach to a solution of the potential problem only, the barrier-controlled characteristics in weak inversion and weak injection (punch-through) are produced efficiently and provide quantitative data for slopes, threshold voltages, and punchthrough voltages, as well as their two-dimensional dependence on device geometry, doping, and terminal voltages. Examples are presented for NMOS transistors with various enhancement and buried channel implants. The program is useful both as a pre-selector for structures to be simulated with a more elaborate two-dimensional potential and transport program and as a generator of parameters for a device model in a circuit simulator.