Correlation of fin shape fluctuations to FinFET electrical variability and noise margins of 6-T SRAM cells

The impact of fin line-edge roughness on threshold voltage and drive current of LSTP-32 nm Fin-FETs is estimated through TCAD simulations. A Monte Carlo approach highlights an increase in the average V_T and a decrease in the average I_ON w.r.t. sensitivity analysis based predictions. Correlations of fin shape fluctuations to electrical performance are investigated. An equivalent fin width is calculated, which allows reducing the spread in I_ON scatter plots and highlights relative importance of LER in different fin regions. Simplified device instances with linearly varying fin width are simulated to better assess the impact of local thinning/thickening in the channel, S and D extensions, revealing asymmetries in the device behavior upon swapping the taper direction. Impact of LER on noise margins of FinFET-based SRAMs is investigated in the hold, read and write mode of cell operation. Results are compared to published data on fabricated cells with similar device features. mu-6sigma statistics helps with assessing variability concerns for mainstream integration of FinFET-SRAMs in future technology nodes.