Investigation on Variability in Metal-Gate Si Nanowire MOSFETs: Analysis of Variation Sources and Experimental Characterization

The characteristic variability in gate-all-around (GAA) Si nanowire (NW) metal-oxide-semiconductor field-effect transistors (SNWTs) is analyzed and experimentally investigated in this paper. First, the main variation sources in SNWTs are overviewed, with the detailed discussion on the specific sources of NW cross-sectional shape variation, random dopant fluctuation in NW source/drain extension regions and NW line-edge roughness (LER). Then, following the measurement-modeling approach, via calibrated statistical simulation that is based on the modified analytical model for GAA SNWTs with corrections of quantum effects and quasi-ballistic transport, the variability sources in SNWTs are experimentally extracted from the measured devices with 10-nm-diameter NW channels and TiN metal gate. The results indicate that NW radius variation and metal-gate work function variation dominate both the threshold voltage and ON-current variations due to the ultrascaled dimensions and strong quantum effects of GAA NW structure. The NW LER also contributes, but relatively less, to the threshold voltage variation.