25 nm CMOS design considerations

This paper explores the limit of bulk (or partially-depleted SOI) CMOS scaling. A feasible design for 25 nm (channel length) CMOS, without continued scaling of oxide thickness and power supply voltage, is presented. A highly 2-D nonuniform profile (super-halo) is shown to yield low off-currents while delivering a significant performance advantage for a 1.0 V power supply. Several key issues, including source-drain doping requirements, band-to-band tunneling, and poly depletion effects, are examined and quantified. It is projected, based on Monte-Carlo simulations, that the delay performance of 25 nm CMOS is 3× higher than 100 nm CMOS, and that the nFET fT exceeds 250 GHz.