A Model for Anomalous Short-Channel Behavior in Submicron MOSFET’s

Abstract

This paper reports experimental data and simulation results on submicron MOSFET’s, which are used to support a physical explanation for two important anomalies in the dependence of device threshold voltage on channel length. The widely observed increase in threshold voltage with decreasing channel length (roll-up), and the more recent observation that the ultimate threshold voltage decrease (roll-off) occurs at a rate which is far in excess of that which can be explained with conventional models of laterally uniform channel doping. A new model is proposed that attributes roll-up as well as roll-off to lateral redistribution of doping near the source and drain junctions. This lateral redistribution is caused by crystal defects formed during post-source / drain-implant anneal. The resulting profile consists of an enhancement of background doping adjacent to the junction edge, bounded by a depression of the doping farther into the channel. © 1993 IEEE