Design Aspects of Carry Lookahead Adders with Vertically-Stacked Nanowire Transistors

This paper discusses the newly introduced vertically-stacked silicon nanowire gate-all-around fieldeffect-transistor technology and its advantages for higher density layout design. The vertical nanowire stacking technology allows very-high density arrangement of nanowire transistors with near-ideal characteristics, and opens the possibility for design optimization by adjusting the number of nanowire stacks without affecting the footprint area of the device. Several libraries for combinational logic synthesis have been designed and implemented for the synthesis of carry-lookahead adders, using the vertically-stacked nanowire technology. The reduction in silicon active area occupancy of vertically-stacked gates are envisaged of great significance for regular cell mapping, in disruptive future applications based on nanowire transistor arrays.