Reverse short channel effect and channel length dependence of boron penetration in PMOSFETs

Abstract

The anomalous increase in reverse-short-channel effect of PMOSFETs, in the presence of boron penetration from the gate, is examined here. Based on an extensive simulation and experimental study, we demonstrate that the degree of boron penetration is a function of the channel length and that long channel transistors are more susceptible to boron penetration compared to short channel devices. This leads to the observed decrease in threshold voltage with increasing channel length and hence, an enhanced reverse-short-channel-like behavior in PMOSFETs. Using length scale arguments, we propose that silicon interstitial absorption into the gate oxide is responsible for blocking boron penetration at the edges of the channel as compared to the middle, thus making the short channel length transistors more immune to boron penetration as compared to long channel length ones.