Charge centers induced in thermal SiO2 films by high electric field stressat 80 K

Charge centers induced in wet and dry SiO2 films by high electric field str ess [Fowler-Nordheim (FN) stress] at 80 K were characterized. The gate curr ent of wet oxides was found to increase steeply during the FN-stress applic ation at 80 K. In contrast, the gate current of dry oxides increased little . The thermally stimulated current of the oxides stressed by a high electri c field and that of oxides irradiated with vacuum-ultraviolet light were me asured. The measurements revealed one negative charge center (tr-1) and thr ee positive charge centers (tr-2-tr-4) in the temperature range of 80-350 K . Their activation energies were estimated to be 0.26 eV (tr-1), 0.50 eV (t r-2), 0.60 eV (tr-3), and 0.86 eV (tr-4). The wet oxides were found to have a higher density of charge centers than the dry oxides. In particular, pos itive charge center tr-3 was characteristic of the wet oxides. The steep in crease in the gate current of the wet oxides during the application of FN s tress is attributed to tr-3. This center appears to be related to H+. (C) 2 001 American Institute of Physics.