RELIABILITY OF ULTRA-THIN GATE OXIDE BELOW 3 NM IN THE DIRECT TUNNELING REGIME

Cluster tool furnace technology was used to control the growth of extr emely uniform ultra-thin 1.5 nm to 3 nm SiO2 layers on Si. The transit ion from Fowler-Nordheim tunneling to direct tunneling electron inject ion for sub-3-nm oxide poly-Si gate metal-oxide-silicon capacitor stru ctures is described and the influence on the oxide reliability is disc ussed. It is shown that oxide breakdown can still occur at low voltage s in the direct tunneling regime under the condition of electron injec tion from the poly-Si gate. Soft breakdown of these ultra-thin oxide l ayers, accompanied by the occurrence of complex fluctuations in the di rect tunneling current, is demonstrated. Using this as the definition of sub-3-nm oxide breakdown, it is shown for the first time that the t ime to dielectric breakdown of the sub-3-nm gate oxide in the direct t unneling regime is determined by the electrical field strength in the oxide similarly to the case of the sub-3-nm dielectric breakdown in Fo wler-Nordheim tunnel stressing.