V. O. Borisov

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.

Plasma-chemical deposition of SiCN films from volatile N-bromhexamethyldisilazane

Process of silicon-carbonitride (SiCN) film production from a new volatile organosilicon, N-bromhexamethyldisilazane, is developed. The use of this chemical comprising the relatively week N-Br bond makes it possible to increase the film growth velocity in the plasma-chemical process with remote plasma in comparison with the processed in which hexamethyldisilazane and hexamethylcyclotrisilazane are used. The chemical composition of the films is determined using a complex of spectroscopic methods. It is found that inorganic SiCN films containing Si-N, Si-C, and C-N bonds are deposited at temperatures 570–870 K. The C-N bonds are formed already at a temperature of about 470 K. It is shown that the use of this volatile organosilicon material makes it possible to synthesize silicon carbonitrides with various ratios of the Si-C, Si-C, and C-N bonds. This enriches the possibilities of producing films and coatings with various functional parameters. The nanohardness of 100-nm films prepared at T > 770 K is 17 GPa.

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).

Effect of the chemical structure of silyl derivatives of unsymmetrical dimethylhydrazine on the composition and structure of silicon carbonitride films: Theoretical and experimental studies

Quantum-chemical calculations are used to analyze the homolytic decomposition of 1,1-dimethyl-2-(dimethylhydrazino)silane (DMDMHS) and bis(2,2-dimethylhydrazino)dimethylsilane (bisDMHDMS)—precursors for the growth of silicon carbonitride films. The results indicate that the homolytic decomposition of DMDMHS is a highly endothermic process, whereas bisDMHDMS decomposition is almost thermally neutral, owing to the strong bond in the N2 molecule. This indicates that the probability of the breaking of the Si-N bond and the formation of volatile silanes, free of nitrogen, is higher in bisDMHDMS, and accounts for the absence of Si-C groups in films grown from this precursor at room temperature. The conclusions drawn from quantum-chemical calculations are supported by experimental data on the growth kinetics, chemical structure, and composition of layers grown from DMDMHS and bisDMHDMS.

Composition and Structure of Films Deposited from Silyl Derivatives of Asymmetrical Dimethylhydrazine

Si–N–C films were produced by remote-plasma chemical vapor deposition using silyl derivatives of asymmetrical dimethylhydrazine as precursors and were characterized by optical spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscopy, and synchrotron x-ray diffraction. The results demonstrate that Si–N and Si–C bonds prevail in the films deposited using excited hydrogen, while the structure of the films deposited using excited helium is dominated by Si–N and C–N bonds. The films contain both amorphous and crystalline silicon carbonitride. The crystalline phase can be indexed in a tetragonal cell with lattice parameters a= 9.6 Å and c= 6.4 Å. The formation of the crystalline phase and the shape of the crystallites are not correlated with the deposition temperature, which gives grounds to believe that the crystallization process may occur in the gas phase or on the film surface as a result of the increase in mechanical stress with increasing film thickness.

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

X-ray photoelectron spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy (over thickness profiling of the elemental and phase compositions of the samples) are used to investigate the elemental and phase compositions, structures, and microstructures of films synthesized in La–Hf–O and Sc–Hf–O systems from organometallic volatile compounds. The dependence of the phase compositions and microstructures of films on the concentration of a doping rare earth element is determined. It is found that lanthanum and scandium doping of hafnium oxide results in the formation of solid solutions of a hightemperature cubic modification. The conditions for obtaining the pyrochlore phase are determined in the nanocrystalline Hf–La–O system.