In-situ doped and tensily stained ge junctionless gate-all-around nFETs on SOI featuring I<inf>on</inf> = 828 μa/μm, I<inf>on</inf>/I<inf>off</inf> ? 1×10<sup>5</sup>, DIBL= 16-54 mV/V, and 1.4X external strain enhancement
Journal
International Electron Devices Meeting, IEDM
Journal Volume
2015-February
Journal Issue
February
Pages
9.6.1-9.6.4
Date Issued
2015
Author(s)
Wong, I.-H.
Chen, Y.-T.
Huang, S.-H.
Tu, W.-H.
Chen, Y.-S.
Shieh, T.-C.
Lin, T.-Y.
Lan, H.-S.
Abstract
In-situ CVD doping and laser anneal can reach [P] and tensile strain as high as 2×10 20 cm -3 and 0.34%, respectively, in Ge on SOI with low defect density and high activation rate (nearly 100% near the surface), and enables high performance of the junctionless (JL) Ge gate-all-around (GAA) nFETs. The device with the W fin of 13 nm, EOT of 10 nm, and nominal L G of 280 nm has I on = 350 μA/μm, I on /I off = 3×10 6 , SS = 185 mV/dec, and DIBL = 16 mV/V. The device with the W fin of 9 nm and EOT of ~ 0.8 nm achieves the record high I on of 828 μA/μm at V GS - V T = 1.5 V and V DS = 2 V with DIBL = 54 mV/V, I on /I off = 1×10 5 and SS = 150 mV/dec. Besides the epitaxial tensile strain (0.34%) generated by laser anneal due to the misfit of thermal expansion coefficients between Ge and Si, the enhanced tensile strain by the microbridge structure is also beneficial for I on . The drain current enhancement of ~40% is achieved under the mechanical uniaxial tensile strain of ~0.25% due to sub-band splitting and carrier repopulation into the L4 valleys with the small conductive effective mass. The non-uniform shape of Ge channel with a minimum width at the center leads to enhanced I on as compared to uniform channel. The extracted mobility of JL devices increases with increasing temperature, indicating the domination of impurity scattering. The threshold voltage of JL devices has the negative temperature coefficient and EOT scaling reduces the temperature dependence.
Type
conference paper