L. V. Yakovkina

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.

Plasma-Enhanced Chemical Vapor Deposition of Silicon Carbonitride Films from Volatile Silyl Derivatives of 1,1-Dimethylhydrazine

Silicon carbonitride films were synthesized from new volatile precursors by plasma-enhanced chemical vapor deposition. Based on a detailed study of the morphology of film surfaces, it was found that the layer material was an amorphous matrix with inclusions of nanosized crystals. Calculation of the structure of the crystalline phase from synchrotron X-ray diffraction patterns demonstrated that the entire set of the diffraction peaks detected is indexed by a tetragonal structure with the lattice parameters a = 9.6 Å and c = 6.4 Å. This is consistent with the fact that the carbon 1s and nitrogen 1s core level X-ray photoelectron spectra exhibited only sp3 bonding, which was expected for superhard carbon nitride phases.

Microstructure and Chemical Bonding in Silicon Carbonitride Films Synthesized by Plasma Enhanced Chemical Vapor Deposition

Silicon carbonitride films were synthesized by plasma enhanced chemical vapor deposition using silyl derivatives of asymmetric dimethylhydrazine, (CH3)2HSiNHN(CH3)2 and (CH3)2Si[NHN(CH3)2]2, as molecular precursors. The film material consists of an amorphous matrix with nanocrystalline inclusions. Indexing of synchrotron radiation X‐ray diffraction patterns suggests that the structure of the nanocrystals is tetragonal with lattice parameters a = 9.6Å and c = 6.4Å. X‐ray photoelectron spectra indicate that Si—N and C—N sp3 hybrid bonds are predominant. The absence of G‐ or D‐modes in Raman spectra, which are otherwise typical of structures possessing sp2 bonding, provides further support for the tetragonal structure of the nanocrystals.

Synthesis and properties of dielectric (HfO2)1 − x(Sc2O3)x films

Abstract(HfO2)1 − x(Sc2O3)x films have been grown by chemical vapor deposition (CVD) using the volatile complexes hafnium 2,2,6,6-tetramethyl-3,5-heptanedionate (Hf(thd)4) and scandium 2,2,6,6-tetramethyl-3,5-heptanedionate (Sc(thd)3) as precursors. The composition and crystal structure of the films containing 1 to 36 at % Sc have been determined. The results demonstrate that, in the composition range 9 to 14 at % scandium, the films are nanocrystalline and consist of an orthorhombic three-component phase, which has not been reported previously. Using Al/(HfO2)1 − x(Sc2O3)x/Si test structures, we have determined the dielectric permittivity of the films and the leakage current through the insulator as functions of scandium concentration. The permittivity of the films with the orthorhombic structure reaches k = 42–44, with a leakage current density no higher than ∼10−8 A/cm2.

Structure and properties of films based on HfO2-Sc2O3 double oxide

The results of the investigation of the chemical constitution and structure of (HfO2)x(Sc2O3)1−x thin films are reported. The films are obtained by chemical vapor deposition (CVD) from hafnium 2,2,6,6-tetramethyl-3,5-heptandionate (Hf(thd)4) and scandium 2,2,6,6-tetramethyl-3,5-heptandionate (Sc(thd)3) coordination compounds. It is demonstrated by powder X-ray diffraction and infrared spectroscopy that depending on the scandium content in the films the structure is changed from monoclinic to cubic. Voltage-capacity dependences of test Al/(HfO2)x(Sc2O3)1−x/Si structures are used to calculate the dielectric constant of the films. For the films with the cubic structure it is found that k = 21, while for the films with the monoclinic structure k = 9.

Structure of HfO2 films and binary oxides on its base

The chemical composition and structure of HfO2 films and binary oxides formed by their doping with aluminum and scandium are analyzed. It is shown that aluminum doping of HfO2 causes film amorphization: at the Al concentration above 30 at.% the film becomes amorphous. Scandium doping of HfO2 modifies the monoclinic structure, and in the Sc concentration range from ∼9 at.% to ∼14 at.% Sc under non-equilibrium conditions of the CVD process at 600°C a solid solution film of the orthorhombic structure forms.

Growth, chemical composition, and structure of thin LaxHf1 − xOy films on Si

The chemical structure, phase composition, and crystal structure of LaxHf1 − xOy films grown on Si using volatile metalorganic compounds as Hf and La precursors have been studied by X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray microanalysis, and atomic force microscopy. By varying the lanthanum and hafnium source temperatures, we were able to grow films with 2 at % < CLa < 30 at %. The Hf 4f and La 3d peak positions in the XPS spectra of the films correspond to hafnium and lanthanum in the Hf4+ and La3+ states. With increasing La concentration, the reflections in the X-ray diffraction patterns of the films shift to smaller 2θ angles, indicating the formation of solid solutions. At 18 at % La, we observed a transition from a fluorite-like structure to the pyrochlore structure (La2Hf2O7). The film containing 30 at % La consisted of a mixture of c-La2O3 and La2Hf2O7. The surface roughness of the films was shown to increase with increasing La concentration. Capacitance-voltage (C-V) measurements were used to assess the relative permittivity (k) of the films as a function of La concentration. The minimum k value was obtained at the La concentration corresponding to the transition from the fluorite structure to an ordered pyrochlore structure (second-order phase transition).

Thermodynamic approach to optimization of SrTiO3 chemical vapor deposition from volatile metalorganic precursors

AbstractThermodynamic analysis is used to examine the possibility of producing SrTiO3 films in two precursor systems containing different volatile Ti compounds: TiO(dpm)2–Sr(dpm)2–N2O–Ar (I) and Ti(OPri)2(dpm)2–Sr(dpm)2–N2O–Ar (II). The results demonstrate that, at an initial Ti : Sr atomic ratio of 1 : 1 and a ratio of flow rates

Phase composition of nanosized oxide film structures based on lanthanum and scandium doped HfO 2

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