Real Transistor Research Articles

Physical and CAD models for the implanted-channel VLSI MOSFET

A new approach is described for the modeling of practical MOS transistors that have nonuniform substrate doping profiles. The threshold characteristic is used to provide an accurate measure of body charge and thereby to give operating point dependences of the threshold voltage, body effect, mobility, and weak-inversion conduction. The results are incorporated into a simple and flexible CAD model suitable for existing and foreseeable devices. The model has continuity of current and all derivatives throughout all regions of operation. It provides an accurate representation of real transistors and minimizes numerical problems of convergence and stability. It has been implemented as level-4 in SPICE 2G.5 and is freely available for VLSI circuit design.

Three-Dimensional Small-Signal Analysis of Bipolar Transistors

One-dimensional transistors are well-understood today; computer techniques for detailed large-signal and small-signal analyses are available. Real transistors are three-dimensional, however, and lateral effects are only understood qualitatively. Accurate modeling of lateral effects cannot be accomplished without quantitative analyses of three-dimensional transistors. Unfortunately, even the simplest analysis of lateral effects leads to a partial differential equation. In this paper, a fast and accurate numerical technique is used to solve the partial differential equation. This makes feasible a three-dimensional small-signal analysis of transistors operating in the low-injection regime. Calculated h-parameters for a high-frequency, double-diffused, silicon transistor are in good agreement with experimental values.