Experimental verification of SRAM cell functionality after hard and soft gate oxide breakdowns

The effect of hard and soft gate oxide breakdown on SRAM cells is investigated experimentally. SRAM cells based on two FET widths are used. We demonstrate that while SRAM cells with wide gates can retain information even after a hard breakdown, SRAM cells with more typical, narrow gates fail after a hard breakdown of the same magnitude. This is because the narrow FETs cannot compensate the additional current flowing through the hard breakdown path. However, both types of SRAM cells can retain information after their gate oxide undergoes soft breakdown. Soft breakdown is the expected mode of gate oxide failure at operating conditions in present and upcoming CMOS technologies.