Low-Frequency Noise Assessment of Vertically Stacked Si n-Channel Nanosheet FETs With Different Metal Gates

This article presents a comparative low-frequency noise (LFN) characterization of gate-all-around nanosheet n-channel Si metal-oxide-semiconductor field effect transistors, processed with three different metal gates (MGs): an aluminum-based reference process and two alternative effective work function (EWF) stacks. In all cases, the gate dielectric is composed of HfO₂ over an SiO₂ interfacial layer. The LFN figures of merit are extracted, such as the oxide trap density and Coulomb scattering coefficient, and the correlations with the threshold voltage and the electron mobility are investigated. Carrier number fluctuations are confirmed as the dominant mechanism of the 1/f noise for all evaluated devices. Additionally, it is shown that the specific MG can contribute to the carrier scattering, degrading the electron mobility. The most promising results are obtained for one of the alternative MGs, exhibiting a low oxide trap density level, a low threshold voltage and insignificant mobility degradation.