Process steps for a double gate MOSFET with vertical layout

In addition to the high demands on lithography, short channel behaviour is a problem for miniaturisation of devices. Double gate MOSFETs are known to improve the short channel effect and are traded in the ITRS roadmap as a part of non-classical CMOS, which can provide a path to scaling MOSFETs below the 65 nm node. For the centre of a special vertical layout a silicon web with 300 nm height and 20 nm width is required. The web lines are made by electron beam lithography with hydrogen silsesquioxane (HSQ) as negative tone resist. 23 nm wide and 100 nm high lines in HSQ were attained. The transfer of the structures to substrate by dry etching results in 30 nm wide and 300 nm high silicon lines. First transistors with a channel length of 100 nm and gate oxide thickness of 6 nm were fabricated. These first transistors show transconductances of up to 40 μS/μm.