50-nm vertical sidewall transistors with high channel dopingconcentrations

摘要

Vertical MOSFETs have been proposed in the roadmap ofsemiconductors as a candidate for sub 100 nm CMOS technologies. Aprocess flow using sidewall gates and implantations instead of multiplelayer depositions reduces process complexity and offers better CMOScompatibility. High doping concentrations in the channel are needed forsub 100 nm devices. Especially for vertical transistors the uniformchannel doping is more critical than for a planar technology, whereoptimized profiles can be easier implemented. Therefore, we investigatedfor the first time vertical MOSFETs with high channel dopingconcentration up to 1*1019 cm-3 and channellengths down to 50 nm. The impact of the high doping levels on thresholdvoltage and on tunneling currents is discussed. Finally, by using slightprocess modifications first results on vertical double gate MOSFETs willbe presented, which in principle can operate with an undoped channelregion