Y. C. Cheng

Nitridation‐enhanced conductivity behavior and current transport mechanism in thin thermally nitrided SiO2

Conduction enhancement characteristics and the conduction mechanism in nitroxide are reported in this paper. Thermally grown oxides with various thicknesses were nitrided in pure ammonia for different nitridation times. Conduction in thick oxide after short‐time nitridation is dominated by Fowler–Nordheim tunneling with lowered barrier height. A trap‐assisted tunneling model was used to explain the effect of the degree of nitridation on current enhancement in heavily nitrided films. A theoretical calculation was carried out to fit the theory to the experimental results, and the trap density and trap energy level were found to be in the ranges of 1.2×1019–7.2×1020 cm−3 and 2.46–2.56 eV, respectively. These results are explained satisfactorily by the Auger spectroscopic data.

Characterization of Si‐SiO2 interface traps in p‐metal‐oxide‐semiconductor structures with thin oxides by conductance technique

There has been a substantial effort made on the application of Nicollian–Goetzberger’s conductance technique to probe the Si‐SiO2 interface traps on n‐type substrates. However, it was reported that conductance measurement on the p‐type substrate was impossible due to the strong surface potential fluctuations. By using metal‐oxide‐semiconductor (MOS) capacitors with thin (88–434 A) oxides to damp out the fluctuations arising from the interface charge inhomogeneities, it is possible to carry out an accurate conductance measurement on as‐oxidized p‐MOS capacitors. A systematic dependence of the interface trap density on the oxide thickness and oxidation temperature is observed. The hole capture cross sections have no obvious dependence on the process conditions, but show an exponential dependence on the energy. Both the magnitude and bias dependence of the measured time‐constant dispersion parameters are found to be much larger than those theoretically predicted. Results of numerical simulation show that the...

A new model for the growth of silicon dioxide layers

A new model is proposed to account for the growth of both thin and thick silicon dioxide layers. The main assumption of the model is the presence of an exponential distribution of total net charges during oxidation, which strongly affects the oxidation kinetics if the oxidizing species is in ionic form. Theoretical calculation, taking into account the influence of this internal electric field, agrees reasonably well with experimental data covering both thin and thick oxides. The model can be reduced to the well‐known formula of Deal and Grove in the limit of thick oxide, and can also explain satisfactorily the effect of an external field on the oxidation rates.

Instabilities of metal-oxide-semiconductor transistor with high-temperature annealing of its gate oxide in ammonia

This paper deals with the instabilities of the metal‐oxide‐semiconductor (MOS) transistors with nitrided oxides as gate insulators. In order to relate, and to trade off among, the instabilities, the noise behaviors, and other electrical characteristics in these devices, extensive investigations on the electrical properties—including the flatband‐voltage shift, fixed‐oxide charge, interface‐state density, surface mobility, transconductance, and the electronic conduction in the insulating layer—were conducted with various amounts of hot‐electron injections. From the noise‐temperature and the interface‐state density measurements, we found that the electronic trap density at the nitrided‐oxide/silicon interface is significantly enhanced at around an energy level of 0.43 eV below the conduction‐band edge of silicon. On the other hand, results also suggest that the nitridation of the gate insulator in a MOS transistor can improve the stabilities again by hot‐electron bombardment, but suppresses the electron con...

Comment on ‘‘A new model of the rapid initial oxidation of silicon’’

The basic assumptions of a recent model of the rapid initial oxidation of silicon by Schafer and Lyon are examined. It is found that the hypothesis is inconsistent with existing experimental data. Instead, our previous model on initial oxidation is used to satisfactorily explain their experimental data. The charge density at the interface and the equilibrium concentration of oxygen in the oxide are estimated based on this model, which agrees well with measured results. These comparisons suggest that our previous model of oxidation gives an overall satisfactory picture of the rapid initial thermal oxidation of silicon.

Characterization of metal‐oxide‐semiconductor transistors with very thin gate oxide

Metal‐oxide‐semiconductor field‐effect transistors with very thin (100–400 A) gate oxides are fabricated. With improved procedures for extracting the various physical parameters from the capacitance‐voltage curves and carefully controlled experiments, it is confirmed that the fixed oxide charge density increases inversely with the oxide thickness. The surface mobilities at both room temperature and 77 K are also characterized. It is found that the mobility in general decreases as the oxide thickness is reduced. The mobility results are interpreted in terms of the coulomb and surface roughness scattering. A plausible model explaining the correlation of oxide thickness, growth condition, and the above physical parameters is also proposed.

An analytical model for the inverse narrow‐gate effect of a metal‐oxide‐semiconductor field‐effect transistor

A closed‐form analytical expression is derived to predict the threshold voltage of a narrow‐gate metal‐oxide‐semiconductor field‐effect transistor with a fully recessed field‐isolation structure. The calculation is based on a simple conformal transform and a physical model employing the depletion approximation. The physical origin of the inverse narrow‐gate effect is mentioned. Threshold‐voltage variations under the influence of various physical parameters are discussed, and a comparison with published data shows that the present model is useful.

A new model for dielectric-breakdown phenomenon in silicon dioxide films

A new model is proposed to interpret the breakdown phenomenon of dielectric thin films such as SiO2 films over the whole range of an applied field. It is suggested that two main mechanisms are responsible for the dielectric breakdown which is influenced by the geomorphic and physical parameters, and the examination conditions. One of the mechanisms is the avalanche breakdown, the so‐called intrinsic type, which is caused by impact ionization. The other, the extrinsic type, is the filament‐heating transport which induces a destructive breakdown. A simple mathematical model invoking the role of photon absorption is constructed to describe the effects of the band gap and the insulator thickness on the dielectric breakdown. It can be deduced from the model that (i) the mean distance of impact ionization is equivalent to the minimum thickness of the film generating the impact ionization and (ii) the probability of impact ionization is a function of the width of the band gap of the insulator under an applied fi...

A new growth model of thin silicon oxide in dry oxygen

This paper presents a new growth kinetic model for thermal oxidation of silicon in dry oxygen, taking into account the effect of charged oxygen on the growth rate. Two parallel oxidizing species are assumed to be transported during oxidation, i.e., neutral ones via interstitial sites and charged ones through the network. The kinetic model has sufficient physical justifications and agrees with a recent dry oxidation study using 18O/16O sequential treatment. The model is found to correlate very well with experimental data at an O2 pressure of 1 atm in the temperature range 850–1000 °C in dry oxygen for both 〈100〉 and 〈111〉 silicon. Special emphasis is placed on the thin initial regime (10–300 A) where this model is in excellent agreement with the experiments. The maximum error does not exceed 0.2 A/min in the curve fitting.

Modification of open‐circuit voltage of metal‐insulator‐semiconductor solar cells due to a nonuniform insulating layer

The effect of nonuniformity of the insulating layer on metal‐insulator‐semiconductor, open‐circuit voltage is examined. It is based on a simplified model in which insulator limits the dark current via different effects. The enhancement in Voc could be greatly degraded by surface roughness.