Breakdown and defect generation in ultrathin gate oxide

In this work the dielectric reliability of thermally grown ultrathin 3 nm SiO2 layers in poly-Si/SiO2/Si structures is examined. This is compared with a study of the defect generation in the 3 nm gate oxide during tunnel injection of electrons. In these ultrathin SiO2 layers, direct tunneling of electrons becomes very important. An increase of the direct tunnel and Fowler-Nordheim tunnel current during high-field stressing was observed and is explained by the creation of a positive charge in the oxide associated with slow interface traps. It is demonstrated that a higher current instability corresponds with a lower charge to breakdown value (Q(BD)) of the oxide. From these results we conclude that the creation of slow interface traps is an important precursor effect for the 3 nm gate breakdown. (C) 1996 American Institute of Physics.