Unified Model for Electric Fields in LDD-Type MOSFETs

A self-consistent analytic model is proposed for the lateral and transversal fields in an LDD-type MOSFET and is compared with simulations and experiments. The relevant formulae are based on a 2-D potential band model. An LDD MOSFET exhibits in general three lateral field peaks, one at the source, and two at the drain side. They are governed by different mechanisms and all three can cause hot carrier degradation at different biasing conditions. The model is formulated in terms of independent local parameters into which device and technology data must be translated to predict the dependence of the electric field upon various process parameters. The model allows a straightforward explanation of a variety of experimental measurements of substrate and gate currents, and degradation behavior of LDD MOSFETs.