Breakdown measurements of ultra-thin SiO₂ at low voltage

MOSFETs with oxide thickness from tox = 1.4 to 2.2 nm have been stressed for times exceeding one year, at voltages in the range Vg = 1.9-4 V. The data are compared with previous model calculations. The voltage acceleration of the charge-to-breakdown (QBD) is explained in terms of a weak yet statistically significant voltage dependence of the critical defect density at breakdown (NBD), and a stronger than expected voltage dependence of the defect generation probability (Pg) for the thinnest oxides studied.