Device- and Circuit-Level Variability Caused by Line Edge Roughness for Sub-32-nm FinFET Technologies

Abstract

The variability impact of line edge roughness (LER) on sub-32-nm fin-shaped FET (FinFET) technologies is investigated from both device- and circuit-level perspectives using computer-aided design simulations. Resist-defined FinFETs exhibit sizeable device performance variation (up to 10% fluctuation in threshold voltage and 200% in leakage current) when subjected to fin roughness up to 1 nm root-mean-square amplitude. Spacer-defined FinFETs show negligible device performance variation and exhibit quadratic dependence with LER amplitude. For both patterning technologies, the resulting impact on large-scale digital-circuit performance variation is found to be minimal in terms of the overall delay mean and variation. This is attributed to self-averaging of uncorrelated LER effects between individual devices within the circuits, resulting in minimal delay impact for digital-circuit design. The impact of LER on leakage power variation is also found to be minimal for all technologies; however, the mean value increases by up to 40% for 15-nm resist FinFETs. On this basis, the impact of LER on sub-32-nm FinFET device-level variability is only significant for resist devices, whereas the resulting digital-circuit impact is important only in terms of mean leakage power increase.