Direct measurement of V/sub th/ fluctuation caused by impurity positioning

This paper studies a local fluctuation of channel impurity on the source edge. Our direct measurement successfully separates the local (intra-FET) and global (inter-FET) factors. The quite local region (/spl Lt/L/sub eff//spl times/W/sub eff/) significantly affects V/sub th/ distribution in a high V/sub d/, which exceeds the global factor in the smallest MOSFETs. The local fluctuation inevitably affects MOSFETs in SRAM cells even though global fluctuation is reduced by process optimization.