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 com pared with a study of the defect generation in the 3 nm gate oxide dur ing tunnel injection of electrons. In these ultrathin SiO2 layers, dir ect tunneling of electrons becomes very important. An increase of the direct tunnel and Fowler-Nordheim tunnel current during high-field str essing was observed and is explained by the creation of a positive cha rge in the oxide associated with slow interface traps. It is demonstra ted that a higher current instability corresponds with a lower charge to breakdown value (Q(BD)) of the oxide. From these results we conclud e that the creation of slow interface traps is an important precursor effect for the 3 nm gate breakdown. (C) 1996 American Institute of Phy sics.