V. A. Gritsenko

Excess silicon at the silicon nitride/thermal oxide interface in oxide–nitride–oxide structures

The chemical composition and structure of Si3N4/thermal (native and wet) SiO2 interface in oxide–nitride–oxide structures are studied by using secondary ion mass spectroscopy, electron energy loss spectroscopy (EELS) and Auger electron spectroscopy (AES) measurements. EELS and AES experiments show the existence of excess silicon at the Si3N4/thermal SiO2 interface. Excess silicon (Si–Si bonds) at Si3N4/SiO2 interface exists in the form of Si-rich silicon oxynitride. Numerical simulation of the Si–Si bond’s electronic structure by using semiempirical quantum-chemical method (MINDO/3) shows that Si–Si defects act as either electron or hole traps. This result explains the abnormally large electron and hole capturing at this interface reported earlier.

Short-range order in non-stoichiometric amorphous silicon oxynitride and silicon-rich nitride

By de-convoluting the Si 2p X-ray photoelectronic spectra, it was found that the short-range order in amorphous silicon oxynitride ðSiOxNyÞ films with different compositions can be quantitatively described by the random bonding model. In this model the SiOxNy consists of five types of randomly distributed tetrahedra and it indicates that metal– oxide–semiconductor transistor with this gate dielectric will not result in any gigantic potential fluctuation in the conduction channel. On the contrary, the structure of silicon-rich silicon nitride SiNx can only be described by the random mixture model where the local composition fluctuations in this film will result in gigantic potential contravariant fluctuation. 2002 Elsevier Science B.V. All rights reserved.

Electronic structure of δ-Ta2O5 with oxygen vacancy: ab initio calculations and comparison with experiment

Electronic structure of oxygen vacancies in Ta2O5 have been studied theoretically by first-principles calculations and experimentally by x-ray photoelectron spectroscopy. Calculations of δ-Ta2O5 were performed using density functional theory within gradient-corrected approximation with the +U approach. Results indicate that the oxygen vacancy causes a defect level in the energy gap at 1.2 eV above the top of the valence band. To produce oxygen vacancies, amorphous films of Ta2O5 were bombarded with Ar+ ions. XPS results indicate that the Ar-ion bombardment leads to the generation of the oxygen vacancies in Ta2O5 that characterize the peak at 2 eV above the valence band. The calculated spectrum of crystalline δ-Ta2O5 demonstrates qualitative correspondence with the XPS spectrum of the amorphous Ta2O5 film after Ar-ion bombardment.

Electronic structure of α-Al2O3: Ab initio simulations and comparison with experiment

Al2O3 films 150 Å thick are deposited on silicon by the ALD technique, and their x-ray (XPS) and ultraviolet (UPS) photoelectron spectra of the valence band are investigated. The electronic band structure of corundum (α-Al2O3) is calculated by the ab initio density functional method and compared with experimental results. The α-Al2O3 valence band consists of two subbands separated with an ionic gap. The lower band is mainly formed by oxygen 2s states. The upper band is formed by oxygen 2p states with a contribution of aluminum 3s and 3p states. A strong anisotropy of the effective mass is observed for holes: mh⊥* ≈ 6.3m0 and mh‖* ≈ 0.36m0. The effective electron mass is independent of the direction me‖* ≈ me⊥* ≈ 0.4m0.

Silicon dots/clusters in silicon nitride: photoluminescence and electron spin resonance

Abstract Photoluminescence (PL) properties of SiN x (0.51 x x is proposed to explain these observations. In addition, non-radiative recombination centers (N 3 Si·, N 2 SiSi·, NSi 2 Si·, or Si 3 Si·), which have prominent effect on the luminescence intensity, are also studied using electron spin resonance (ESR) measurement. The ESR results suggest that the excess silicon content should not be too high in order to have a strong PL.

Two-bands charge transport in silicon nitride due to phonon-assisted trap ionization

The charge transport in the amorphous Si3N4 is studied experimentally and theoretically. We have found, that widely accepted Frenkel model of the trap ionization gives the unphysical low value of the attempt to escape factor, and the enormously high value of the electron tunnel mass. Experimental data are well described by theory of the two-bands conduction and the phonon-assisted trap ionization in Si3N4.

Charge transport mechanism in amorphous alumina

The charge transport mechanism in amorphous Al2O3 was examined both experimentally and theoretically. We have found that electrons are dominant charge carriers in Al2O3. A satisfactory agreement between the experimental and calculated data was obtained assuming the multiphonon ionization mechanism for deep traps in Al2O3. For the thermal and optical trap ionization energies in Al2O3, the values WT=1.5 eV and Wopt=3.0 eV were obtained.

Electronic Structure of Silicon Dioxide (A Review)

Silicon dioxide amorphous films are the key insulators in silicon integrated circuits. The physical properties of silicon dioxide are determined by the electronic structure of this material. The currently available information on the electronic structure of silicon dioxide has been systematized.

Bonding and band offset in N2O-grown oxynitride

Using high-resolution angle-resolved x-ray photoelectron spectroscopy (ARXPS) measurements, the chemical bonding, and valance-band offset of ultrathin (16 and 24 A) N2O-grown oxide were studied. We confirmed that the composition of N2O-grown oxide is mainly silicon oxide with both the concentration and band offset values measured using ARXPS. The surface density of nitrogen is about (3±1)×1014 cm−2 near the Si/dielectric interface. The valence- and conduction-band offsets for N2O-grown oxide are the same as those for the Si/SiO2 interface because the nitrogen content is too low to have any pronounced effects. In addition, we found that most of the nitrogen atoms at the interface appeared in the form of Si–N bonding instead of N–O bonding.

Composition and structure of hafnia films on silicon

Ellipsometry, electron microscopy, and x-ray photoelectron spectroscopy data indicate that, during HfO2 deposition onto silicon, the native oxide reacts with the HfO2 deposit to form an amorphous intermediate layer which differs in refractive index (≃1.6) from both HfO2 (1.9–2.0) and SiO2 (1.46). Thermodynamic analysis of the Si-SiO2-HfO2-Hf system shows that Si is in equilibrium with Si/HfO2 − y only at low oxygen pressures. Starting at a certain oxygen pressure (equivalent to the formation of a native oxide layer), the equilibrium phase assemblage is Si/HfSiO4/HfO2 − y.