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

摘要

The impact of fin line-edge roughness on threshold voltage and drive current of LSTP-32nm Fin-FETs is estimated through TCAD simulations. A Monte Carlo approach highlights an increase in the average VT 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. μ - 6σ statistics helps with assessing variability concerns for mainstream integration of FinFET-SRAMs in future technology nodes.