Measurements of characteristics of the inversion channel conductivity of MOS-transistors after the ion polarization and depolarization of samples in the range of values of the induction of the transverse magnetic field of 0 – 5 T at temperatures from 100 K to 200 K were carried out. After the ionic polarization at 420 K under the action of a strong electric field in the oxide at least 6·1013 cm-2 ions flowed. The previously observed increase of the conductivity in the source-drain circuit after the polarization of insulating layers is up to 10 times explained by the formation of a new electrical transfer path through the surface impurity band, associated with delocalized D– states, that are generated by neutralized ions located in the insulating layer at the interface with a semiconductor.
Results of experimental studies of the stability of metal-oxide-semiconductor (MOS) structures with an oxide thickness of less than 40 Å to the effect of strong, but before breakdown electric fields are analyzed. It turned out, that objects with an ultra-small thickness of SiO2 are much more "submissive" to the field stress – they are more easily damaged by external influences, but they are much more quickly restored to their original state at the room temperature. In the process of the exposure of structures in a strong electric field, additional localized electronic boundary states with a concentration exceeding 1013 cm-2 at the silicon-oxide contact are formed. Recharging of newly formed centers with increasing field voltage certainly ensures the accumulation of an excess charge at the silicon-oxide interface, sharply increasing field in the insulating layer. This phenomenon should have a decisive influence on the change in tunnel current-voltage characteristics of Si-MOS structures after the field stress.
Ferroelectric nanodomains were created in Ba0.8Sr0.2TiO3 (BST 80/20) thin films by applying a voltage to a sharp conducting tip of a scanning probe microscope (SPM). The ferroelectric layer were grown on (100)-oriented silicon substrate by radio frequency magnetron sputtering. The surface of the sample shows small grains which diameter ranges from 50 nm to 75 nm and roughness is less than 5 nm. Using the piezoresponse mode of the SPM to detect the out-ofplane film polarization, the domain sizes were measured as a function of the applied writing voltage and the pulse time. It was found that the time dependence of the domain diameter in a 400 nm thick BST 80/20 film well described by logarithmic law observed earlier in Pb(Zr0.2Ti0.8)O3 (PZT) films. The dynamics of domain growth is analyzed theoretically taking into account the strong inhomogeneity of the external electric field in the film and the influence of the bottom electrode. Therefore, the BTS film with good polarization switching properties could act as a memory element in nonvolatile ferroelectric random access memory (NV-FRAM) devices.
The analysis algorithm of quasistatic C-V-characteristics of MIS-structures in the range of the depletion of the semiconductor
surface of main carriers of the charge are developed. This algorithm provides the quantitative determination of a
concentration of doping impurity, the <<flat bands>> voltage and efficient values of a capacity and a thickness of a gate insulator.
On this data, obtained within the framework of the single experiment on the Al-SiO2-(100) n-Si MOS-structure, dependencies
of ψs(Vg),Qs[ψs(Vg)] and Vi(Vg) (where ψs and Qs - a surface potential and a density of the surface charge in n-Si, Vg - a gate potential, Vi - a voltage drop on an oxide) are reduced. These dependencies without any a priori information about the
state of the electronic gas under the strong accumulation or deep inversion are found. Experimental curves of ψs(Vg) and Qs[ψs(Vg)] are possible considered as the criterion of the correct of the theory of the semiconductor space charge region, take
into account electron gas degeneration and quantum confinement effects, as observed maximum layered densities of electrons
and holes exceed 1013cm-2. The dependency of Vi(Vg) necessary to use under investigations of the conductivity through
gate insulators, particularly, in cases their small and ultrasmall of the thickness, when the leakage current is defined basically
by the tunnel effect.
Based on the Hall-Shockley-Read formalism we have successfully demonstrated that of the surface generation of minority carriers (MC) in a semiconductor of the Si-MOS-structure, leaded in the strong in-equilibrium depletion state, is ineffective due to rapid establishment of the quasi-equilibrium between surface generation centers and MC band. At the silicon surface without deep levels MC can be appeared only due to the diffusion from the quasi-neutral region. However, this diffusion takes place only at T> 100°C. Thus, in the perfect Si-MOS-structure at room temperature the state of non-equilibrium depletion can be conserved the infinitely long time, as a MC thermodiffusion from a Si electroneutral volume at the T<100°C is ineffective. In this situation single source of the MC generation is the edge effect. This effect can be artificially enhanced by staggered inhomogeneity gate oxide. Then, in depletion layer under the (thick) oxide the quasi-equilibrium between surface generation centers and MC band will be not established due to continuous MC leakage in the more deep potential well under (thin) oxide. The MC leakage is continued until homogenezation of a semiconductor surface. Next, a MC generation velocity will be determined the edge effect only. Experimental time dependences of the generation current Ig(t) are found to be in accordance with these concepts. On dependences Ig(t) are observed two discrete current steps. The height of steps undepends from depletion voltage Vg and their durability increase with growth of Vg. The MC generation rate and surface recombination velocity were obtained by Ig(t) curves. Increasing of grading of a gate oxide thickness allow to rise a number of steps on the Ig(t) dependence. The edge effect in a MIS-structure easily is increased of external stresses that it is allowed to use the edge effect for the creation sensor-devices of a new type.
The nanometer scaling of metal-oxide-semiconductor (MOS)-devices requires a transition to thin and ultrathin gate insulators. Their tunneling conductance in such insulators essentially changes of the process of the minority carrier (MC) generation. In n-Si-MOS-structures with a insulator thickness below 100Å the tightly growth and sharply dropping peak is appeared on the time dependence of the generation current Ig(t). The peak is completed a transition of a MOS-structure to the equilibrium inversion state. In this state the stationary tunnel current It∞ flows through a MOS-structure. The amplitude peak and its position in the time strongly depend from the structure construction, its prior history and external factors and can to change in wide limits. The sequential description of phenomenon is based on presentations about a impact ionization of the MC band, tunneled through oxide in semiconductor by heat electrons. The developed algorithm allows to divide of the contributions of generation and tunnel current component in dependences I(t, Vg) and to characterize of oxide tunnel conductance. The algorithm too allows to determine set of base electronic characteristics of MOS-structures: the impact ionization coefficient α, sign and integral density of fixed charge in a oxide, a rate of the MC generation and a velocity of the surface recombination, and the time evolution of the semiconductor surface potential. These data are base for the physical diagnostic of degradation mechanisms of the semiconductor/insulator interface region. The strong dependence of kinetics of the thermo-tunnel generation of MC from a composition of a surrounding medium can to use for a creation of gas sensors of new type.
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