Lightly doped Schottky MOSFET

Platinum silicide Schottky barrier p-MOSFETs were built with additional acceptor doping surrounding the S/D areas to increase their current drive and to decrease their drain leakage, while maintaining a low minority carrier injection efficiency into the substrate. Using ion implantation to controllably introduce the S/D dopant we found experimentally that, for the actual prcess used, 3E13 cm-2BF2 is the minimum dose that is required to achieve full current drive. However, the drain leakage does not decrease to a satisfactory level until a dose of 1E14 cm-2is used but the higher dose increases the minority carrier injection into the substrate. An unexpected high series resistance is explained by analyzing the conduction process in the weakly doped regions of the source overlapped by the gate when the polysilicon gate and the S/D regions are doped with opposite type impurities. These devices have direct application for latch-up free CMOS.