Quasi-breakdown of ultrathin gate oxide under high field stress

A new oxide failure mode of ultrathin gate oxide is reported. During high constant current stressing, V/sub G/ variation with time shows two distinct modes, i.e., a stable mode and a fluctuation mode named as quasi-breakdown. Once the quasi-breakdown starts, gate current in low field abruptly increases. From the experimental results, it could be concluded that the quasi-breakdown occurs when injected electrons travel in the oxide conduction band ballistically. Localized physical damage near the Si/SiO/sub 2/ interface is believed to be the cause of the quasi-breakdown, The great increase of gate current after the quasi-breakdown was modeled by a superposition of F-N tunneling current and direct tunneling current with a finite series resistance, and a good agreement has been found.<>