The limit of MOSFET oxide scaling is examined from the viewpoint of reliabi
lity. Measurements of the voltage dependence of the defect generation rate
and the thickness dependence of the critical defect density, together with
the breakdown statistics for ultra-thin oxides, are used to provide a gener
al framework for predicting the lifetime of ultra-thin oxides at operating
voltage. It is argued that reliability is the limiting factor for oxide thi
ckness reduction.