Investigation of tunneling current through thin dielectrics

Currents through SiO/sub 2/ ultrathin dielectric films are used for storage and erase charge in EEPROM. The influence of different parameters such as substrate doping level and type, oxide thickness and post-metalization treatments are investigated in detail. MOS structures with aluminium and polysilicon gates were used for study. The substrate doping level influences the Fowler-Nordheim current significantly and this influence is decreased with increasing oxide thickness. Annealing in hydrogen and in H/sub 2/O reduce the Fowler-Nordheim current. The influence of H/sub 2/O is stronger. In order to explain observed experimental results, the influence of charge at the Si-SiO/sub 2/ interface and in SiO/sub 2/ on experimental I(V) characteristics and corresponding Fowler-Nordheim curves of MOS structures was used. The charge at the Si-SiO/sub 2/ interface and in SiO/sub 2/ was determined by step-by-step etching of silicon dioxide and measurements of C(V) characteristics. The influence of charge build-up in SiO/sub 2/ on the I(V) characteristics of the MOS structure is based on the oxide charge induced tunnel transparency modification. The Fowler-Nordheim current in a MOS structure was calculated in Wentzel-Kramers-Brillouin transparency approximations.