Defect generation and reliability of ultra-thin SiO2 at low voltage

Electrons tunneling through the gate oxide generate defects until a critical density is reached and the oxide breaks down. The critical defect density is explained by the formation of a percolation path of defects across the oxide. The rate of defect generation decreases exponentially with supply voltage, but the tunnel current also increases exponentially with decreasing oxide thickness, leading to a diminishing margin for reliability as device dimensions are scaled.