Shallow junctions on pillar sidewalls for sub-100-nm vertical MOSFETs

A simple process for the fabrication of shallow drain junctions on pillar sidewalls in sub-100-nm vertical MOSFETs is described. The key feature of this process is the creation of a polysilicon spacer around the perimeter of the pillar to connect the channel to a polysilicon drain contact. The depth of the junction on the pillar sidewall is primarily determined by the thickness of the polysilicon spacer. This processis CMOS compatible and, hence, facilitates the integration of a sub-100-nm vertical MOSFET in a planar CMOS technology using mature lithography. The fabricated transistors have a subthreshold slope of 95 mV/dec (at V-DS = 1 V) and a drain-induced barrier lowering of 0.12 V.