N. Zamani

Bio: N. Zamani is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Tunnel effect & Quantum tunnelling. The author has an hindex of 1, co-authored 1 publications receiving 266 citations.

Behavior of the Si/SiO2 interface observed by Fowler-Nordheim tunneling

Abstract: Thin‐oxide (40–50 A) metal oxide semiconductor (MOS) structures are shown to exhibit, prior to large levels of electron tunnel injection, the near‐ideal behavior predicted for a uniform trapezoidal barrier with thick‐oxide properties. The oscillatory field dependence due to electron‐wave interference at the Si/SiO2 interface indicates an abrupt, one‐monolayer barrier transition (∼2.5 A) consistent with earlier work. After tunnel injection of 1017 –5×1018 electrons/cm2, the barrier undergoes significant degradation leading to enhanced tunneling conductance, with reproducible behavior observed among different samples. This effect is consistent with the generation of positive states in the region of the oxide near the Si/SiO2 interface (<20 A), where the tunneling electrons emerge into the oxide conduction band. Densities of positive‐charge and interface‐state buildup are also observed from capacitance‐voltage (C‐V) measurements and are found to be consistent with the observed tunneling dependence on positiv...

Mechanism for stress-induced leakage currents in thin silicon dioxide films

Abstract: Leakage currents introduced in the low‐field, direct‐tunneling regime of thin oxides during high‐field stress are related to defects produced by hot‐electron transport in the oxide layer. From these studies, it is concluded that the ‘‘generation’’ of neutral electron traps in thin oxides is the dominant cause of this phenomenon. Other mechanisms due to anode hole injection or oxide nonuniformities are shown to be unrealistic for producing these currents. Exposure of thin oxides to atomic hydrogen from a remote plasma is shown to cause leakage currents similar to those observed after high‐field stress, supporting the conclusion that these currents are related to hydrogen‐induced defects.

Modeling CMOS tunneling currents through ultrathin gate oxide due to conduction- and valence-band electron and hole tunneling

Abstract: A semi-empirical model is proposed to quantify the tunneling currents through ultrathin gate oxides (1-3.6 nm). As a multiplier to a simple analytical model, a correction function is introduced to achieve universal applicability to all different combinations of bias polarities (inversion and accumulation), gate materials (N/sup +/, P/sup +/, Si, SiGe) and tunneling processes. Each coefficient of the correction function is given a physical meaning and determined by empirical fitting. This new model can accurately predict all the current components that can be observed: electron tunneling from the conduction band (ECB), electron tunneling from the valence band (EVB), and hole tunneling from the valence hand (HVB) in dual-gate poly-Si/sub 1-x/Ge/sub x/-gated (x=0 or 0.25) CMOS devices for various gate oxide thicknesses. In addition, this model ran also be employed to determine the physical oxide thickness from I-V data with high sensitivity. It is particularly sensitive in the very-thin-oxide regime, where C-V extraction happens to be difficult or impossible (because of the presence of the large tunneling current).

Tunneling spectroscopy and inverse photoemission: Image and field states

Abstract: Tunneling spectroscopy performed with the scanning tunneling microscope is used to study image-type surface states. The tunneling tip causes a Stark shift and expansion of the hydrogenic image-state spectrum, permitting a clear resolution of the individual states. A simple theoretical model provides a quantitative connection between the tunneling data and both previous and new inverse-photoemission data.

High-field-induced degradation in ultra-thin SiO/sub 2/ films

Abstract: Very thin thermal oxides are shown to exhibit a failure mode that is undetected by conventional breakdown tests. This failure mode appears in the form of excessive leakage current at low field and is induced by high-field stresses. The stress-induced oxide leakage is permanent and stable with time and thermal annealing. It becomes the dominant failure mode of thin oxides because it always precedes destructive breakdown. Experimental results and theoretical calculations show that the leakage current is not caused by positive charge generation and accumulation in the oxide. It is proposed that the oxide leakage originates from localized defect-related weak spots where the insulator has experienced significant deterioration from electrical stress. The leakage conduction mechanism appears to be thermally assisted tunneling through the locally reduced injection barrier, and the model seems to be consistent with both I-V measurements at temperatures from 77 K to 250 degrees C and theoretical calculations. >