Impact of Cross-Sectional Shape on 10-nm Gate Length InGaAs FinFET Performance and Variability

Abstract

Three cross sections (rectangular, bullet shaped, and triangular), resulting from the fabrication process, of nanoscale In0.53Ga0.47As-on-insulator FinFETs with a gate length of 10.4 nm are modeled using in-house 3-D finite-element density-gradient quantum-corrected drift–diffusion and Monte Carlo simulations. We investigate the impact of the shape on ${I}$ – ${V}$ characteristics and on the variability induced by metal grain granularity (MGG), line-edge roughness (LER), and random dopants (RDs) and compared with their combined effect. The more triangular the cross section, the lower the OFF-current, the drain-induced-barrier-lowering, and the subthreshold slope. The ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ratio is three times higher for the triangular-shaped FinFET than for the rectangular-shape one. Independent of the cross section, the MGG variations are the preeminent fluctuations affecting the FinFETs, with four to two times larger $\sigma {V}_{T}$ than that from the LER and the RDs, respectively. However, the variability induced threshold voltage ( ${V}_{T}$ ) shift is minimal for the MGG (around 2 mV), but ${V}_{T}$ shift increases 4-fold and 15-fold for the LER and the RDs, respectively. The cross-sectional shape has a very small influence in ${V}_{T}$ and OFF-current of the MGG, LER, and RD variabilities, both separated and in combination, with standard deviation differences of only 4% among the different device shapes. Finally, the statistical sum of the three sources of variability can predict simulated combined variability with only a minor overestimation.