S. G. Dmitriev

Distribution of mobile ions in thin insulator films at the insulator-semiconductor interface

The influence of a semiconductor on the mobile ion distribution in insulator thin films at the insulator-semiconductor interface was considered. The degree of ion localization at the interface under the field effect in the film was calculated. The threshold of the ion delocalization with a decrease in the voltage applied to the structure was determined. The relation between the delocalization thresholds and ion current peaks in dynamic current-voltage characteristics of the system is discussed.

Macroscopic ion traps at the silicon-oxide interface

The drift kinetics of the mobile charge in SiO2 films, its capture on ion traps localized at the Si-SiO2 interface, and ion emission from these traps are investigated by measuring the capacitance-voltage characteristics, the dynamic current-voltage characteristics, and the thermally stimulated depolarization current of the insulator. The current components (peaks) associated with the emission of particles trapped on the interface during thermofield treatment are isolated in an explicit form. The charge of the surface ions is shown to be neutralized mainly by Si electrons, and the field dependence of the ion emission currents is characterized by an anomalous Schottky effect associated with opening of the ion-trap potential by the external field. The relationship between these traps and the potential inhomogeneities, i.e., potential wells for mobile particles, on the interface under consideration is discussed. It is noted that the mobile ions in the insulator can be used for interface potential inhomogeneity diagnostics.

Semiconductor surface potential relaxation in the MIS structure in the presence of convective currents in insulator and through its boundaries

It is shown that the Berglund method for determining the metal-insulator-semiconductor surface potential relaxation as the structure voltage changes is valid only in the absence of convective currents in the insulator. A method for determining the potential relaxation in the presence of convective currents is suggested. The currents induced in the structure due to changes in the contact potential difference during temperature variations are also considered.

Relation between currents and charges measured in samples during diagnostics of inhomogeneous insulating films

The relation between currents and charges measured in samples during diagnostics of inhomogeneous insulating films is presented. Examples of multilayer structures, quasi-static diagnostic methods, and other examples are considered taking into account currents through film interfaces.

Sodium-peak splitting in dynamic current-voltage characteristics of convective ion currents in metal-oxide-semiconductor structures

The results of simultaneous measurements of dynamic current-voltage and capacitance-voltage characteristics are presented for metal-oxide-semiconductor structures in the temperature range T = 420–470 K and voltage-sweep rates βv = 0.5–1000 mV/s. The convective currents Icon (V) in oxide are extracted from usual ion currents in the I-V characteristics. In Icon (V) curves, the Na+-ion peaks are split. In addition, an envelope curve is seen in initial portions of “fast” Icon(V) curves with βV ≳ 10 mV/s that indicates to the presence of a certain quasi-steady ion-transport mode. A more equilibrium mode at slow rates βV < 1 mV/s manifests itself in the form of stabilization of convective-current peak shapes. The nature of efficient neutralization of the second peaks in the Icon(V) dependences is discussed.

Separation of dynamic current-voltage characteristics (DCVCs) of an oxide film from the DCVC of ionic currents in a metal/oxide/semiconductor structure: Universal quasi-static DCVCs of a film

Analytic results for a quasi-equilibrium distribution of mobile ions in an oxide film contained in a metal/oxide/semiconductor (MOS) structure, as well as formulas for the concentration of ions at the center of the film and on its boundary and formulas for the ionic centroid, are reviewed. Thresholds for the emergence of a U-shaped distribution of ions with characteristic accumulation of ions near the film’s boundary (segregation of ions) are analyzed; the case of a half-space is considered as well. A method to determine the dynamic current-voltage characteristic (DCVC) of the film’s ionic currents is proposed. This method uses an experimental DCVC of the entire structure and a quasi-equilibrium (low-frequency) electronic voltage-capacitance characteristic of the structure. The film’s DCVC has to be separated to eliminate masking effects of the semiconductor’s capacitance on the structure’s DCVC. An analytic method for calculation of the film’s quasi-static DCVC is developed for a model of a homogeneous film. When expressed in dimensionless units, such DCVCs, which are shown to depend on only the dimensionless concentration of ions in the film (per unit area), prove to be universal functions. The population of ionic traps on the film’s boundary is described using the energy Gibbs distribution of ions. The presence of traps is shown to result in the emergence of an additional “trap” peak on the film’s DCVC only if the concentration of traps is low; when this concentration is large, a single peak is observed on the DCVC.

Manifestations of the deneutralization of mobile charges in SiO2 in the spectroscopy of the silicon-oxide interface

The total number of mobile ions in the oxide film in a Si-based MOS structure is determined by the conventional methods of recording capacitance-voltage and dynamic current-voltage characteristics. The fraction of ions in the neutral state at the Si-SiO2 interface is determined. Spectroscopy of the interface reveals a peak of the effective density of interface states. It is shown that the number of states in this peak corresponds to the number of neutralized particles. The mechanism for neutralization of the mobile charge of ions is discussed.

Segregation of mobile ions on insulator-semiconductor interfaces in metal-insulator-semiconductor structures

The equilibrium distribution of mobile ions was considered in metal-insulator-semiconductor (MIS) structures with ionic surface states at the insulator-semiconductor interface. The quasi-steady currentvoltage characteristics were calculated for ion currents in MIS structures. The population of surface states by ions was described by the Gibbs distribution.

Quasi-static ion currents in thin insulating films of metal-insulator-semiconductor structures and the distribution of ions in the films

A method for calculating the quasi-static current-voltage characteristics for ion currents in a metal-insulator-semiconductor structure is suggested. Theoretical and experimental peaks of ion currents in the current-voltage characteristic were compared. The influence of a semiconductor on the characteristic current-voltage shape was considered. The distribution of ions in the insulator film was calculated. Formulas for determining both the background concentration of ions in thefilm and their concentration at the insulator-semiconductor interface are suggested.

Determination of a Mobile-Ion Concentration in the Dielectric Films of Metal–Insulator–Semiconductor Structures

An experimental technique for determining the surface concentration NSof mobile ions in dielectric films of metal–insulator–semiconductor (MIS) structures is described. The technique is based on synchronous recording of the dynamic volt–ampere and low-frequency capacity–voltage characteristics of a sample under investigation. These experimental dependences are shown to ensure accurate extraction of the ion current peaks whose areas are proportional to NS. These characteristics also allow the relaxation of the surface semiconductor potential to be found, which is needed for reconstructing the dependence of the convection ion current on the voltage drop across the insulation gap of the MIS capacitor. A comparative analysis with other known methods for determining NSis carried out. The proposed technique helps find a mobile-ion concentration from a ∼ 5 × 109to 1013-cm–2range, including the case when ion current peaks do not appear on the current–voltage characteristics.