Non-uniform bipolar conduction in single finger NMOS transistors and implications for deep submicron ESD design

Abstract

This paper presents a detailed study of the nonuniform bipolar conduction phenomenon in single finger NMOS transistors and analyses its implications for deep submicron ESD design. It is shown that the uniformity of lateral bipolar triggering is severely degraded with device width (W) in advanced technologies with silicided diffusions and low resistance substrates, and that this effect can only be improved up to a maximum W by increasing the substrate bias. Additionally, the concept of intrinsic second breakdown strength is introduced, which is substrate bias independent and represents the maximum achievable breakdown current for a given technology.