Variability analysis of the epitaxial layer TFET due to gate work function variation, random dopant fluctuation, and oxide thickness fluctuation using the statistical impedance field method

In this paper, a comparative study on process variability considering work function variation (WFV), random dopant fluctuation (RDF), and oxide thickness fluctuation (OTF) in epitaxial layer tunnel field effect transistor (TFET) with SiGe source (SiGe-ETLTFET) is statistically analyzed using impedance field method (IFM) in Santaurus TCAD tool. Effect of different grain sizes of the gate metal and other device parameter scaling on the variability source are investigated by evaluating the standard deviation of threshold voltage (V (th)), on current (I (ON)), and off current (I (OFF)). At smaller AverageGrainSize, the dispersions in electrical parameters are close to normal, whereas for large AverageGrainSize dispersion increases and deviates from the normal distribution. Compared to RDF and WFV, OTF is not a significant cause of variability in SiGe-ETLTFET. It is found that RDF is the most sensitive variability source while device scaling is concerned. Moreover, L (ov) scaling causes the most acute fluctuation of electrical parameters for all considered variability sources. The slope of the Pelgrom plot, A (VT), of SiGe-ETLTFET considering all variability sources, is smaller than the already reported values for the FinFET and MOSFET.