Fabrication of 32 nm Vertical nMOSFETs with Asymmetric Graded Lightly Doped Drain Structure

The 32 nm channel length vertical negative metal-oxide semiconductor field-effect transistors (nMOSFETs) with asymmetric graded lightly doped drain (AGLDD) structure were experimentally demonstrated. Compared with the conventional LDD structure, due to the reduced peak electric field near the drain junction and the increased potential barrier of the channel in the off state, the vertical AGLDD structure can reduce the off-state leakage current and suppress the short-channel effects dramatically. The fabricated 32 nm AGLDD device with 4.0 nm gate oxide still shows excellent short-channel performance. The off-state leakage current (I off ) and the ratio of on current (I on ) to off-current I off are 3.7 X 10 -11 A/μm and 2.1 X 10 6 , respectively.