Statistical analysis of four write stability metrics in fully depleted silicon-on-thin-BOX (SOTB) and bulk SRAM cells at low supply voltage

Statistical distributions of four write stability metrics at low supply voltage (V
DD
) were measured in 1k fully depleted (FD) silicon-on-thin-BOX (SOTB) and bulk SRAM cells. It is found that butterfly curve shows abnormal “two-mode” distributions, while bit-line and word-line margins maintain good normality even at low V
DD
, which demonstrates bit-line and word-line margins as preferred write stability metrics.