Discussion of the Role of Distributed Effects in Latch-Up

摘要

Latch-up in monolithic integrated circuits, the activation of parasitic four-layer paths capable of regeneration, has long posed a significant reliability problem, especially to the radiation effects community. While methods for the prevention of latch-up have been proposed and implemented, the question of elimination remains at best uneasily answered in the advent of reduced geometries. This seems to be due to a lack of a fundamental understanding of the SCR phenomena in parasitic structures, as proposed solutions have generally been based on a classical analysis or on intuition. Certain distributed and parasitic aspects of four-layer structures that play significant roles in latch-up, i.e., contact and spreading resistance effects and the selection of proper lumped model parameters for the discrete cross-coupled bipolar model, are discussed. The distributed effects of contact resistance and spreading resistance and the drive conditions of the coupled transistor pair are shown to be of particular importance in applying the lumped model theory to parasitic latch-up phenomena and in understanding parasitic latch-up. The lumped model will continue to be a useful conceptualization and analysis vehicle but must allow for additional parasitic elements, and coupled shunt paths must be considered. Possible changes in device parameters reflecting the distributed nature of the devices with changes in modes of operation of the latch-up path should be taken into account. (ERA citation 06:022456)