M. L. Kosinova

Growth of PbS and CdS thin films by low-pressure chemical vapour deposition using dithiocarbamates

Abstract Thin films of cadmium and lead sulphides grown by chemical vapour deposition (CVD) and remote plasma enhanced chemical vapour deposition (RPECVD) using dithiocarbamates as precursors were prepared on fused silica, sapphire, (111)Si and (111)InP substrates. These films were deposited in the temperature range 473–873 K. It was established that the activation energy of the CVD process is 191.5±1.5 kJ mol −1 . The structure of polycrystalline films was halenide for PbS and wurtzite for CdS. It was also found that r.f.-plasma activation of the gas phase decreases remarkably the growth temperature and orders the film structure. RPECVD sulphide films had a high degree of preferred orientation.

Synthesis of nanocrystalline silicon carbonitride films by remote plasma enhanced chemical vapor deposition using the mixture of hexamethyldisilazane with helium and ammonia

Abstract The silicon carbonitride films were synthesised by remote plasma enhanced chemical vapor deposition (RPECVD) using a mixture of ammonia, helium and hexamethyldisilazane Si2NH(CH3)6 as the volatile single-source precursor. Different analysis techniques such as IR, Raman spectroscopy, ellipsometry, X-ray photoelectron spectroscopy, EDS, scanning electron microscopy, high-resolution electron microscopy, selective area electron diffraction and X-ray diffraction using synchrotron radiation were used to study their physical and chemical properties. The formation of chemical bonding was shown to occur between Si, C, N atoms in the ternary compound. The chemical composition of these films depended mainly on the ammonia concentration in the gaseous phase. It was established that there is a distribution of nanocrystals in the amorphous matrix in these films.

The investigation of properties of silicon nitride films obtained by RPECVD from hexamethyldisilazane

Abstract The silicon nitride films were obtained by remote plasma enhance chemical vapor deposition (RPECVD) using hexamethyldisilazane or its mixture with ammonia in the range 373–773 K. The correlations between the chemical composition, deposition rates, optical, electrical and structural properties and the growth conditions were established. It was found that the formation of two polycrystalline hexagonal phases SiC and Si3N4 was realized by using pure hexamethyldisilazane as precursor. The ammonia addition in gas mixture leaded to change of the chemical composition and structure of silicon nitride films, namely, the disappearance of carbon-bonding and SiC formation, and the order of hexagonal silicon nitride.

On thermodynamic equilibria of solid BN and gas phases in the B−N−H−Cl−He system

Abstract Thermodynamic analysis of the chemical vapour deposition (CVD) of boron nitride was performed for the B−N−H−Cl−He system, with new thermodynamic data for different modifications of boron nitride (hexagonal h-BN, cubic c-BN and wurtzite w-BN). The phase equilibria were calculated for the temperature region 673–2273 K, at total pressures of 1.013 × 10 3 and 1.013 × 10 5 Pa and fora wide range of atomic ratios of elements in the system. The results arc presented in the form of CVD phase diagrams which are a good way of illustrating the influence of the system parameters on the formation of stable phases. c-BN is formed in a quasi-equilibrium process at temperatures below 1804 K, the h-BN modification is most stable above this temperature, and w-BN is a metastable phase for all possible variations of the process conditions.

Chemical stability of hydrogen-containing boron nitride films obtained by plasma enhanced chemical vapour deposition

The purpose of this paper is the investigation of the dehydrogenation kinetics of boron nitride films during thermal annealing. BNx:H films on silicon substrates were prepared by remote plasma enhanced chemical vapour deposition at 473 K using a mixture of borazine and helium. IR spectroscopy and ellipsometry were used to characterize the film properties and composition. The films contain a certain amount of hydrogen in BH and NH bonds. The breakage kinetics of these bonds is different. The breakage of NH bonds determines the hydrogen annealing kinetics at 973–1073 K. The low-temperature annealing (673–873 K) of BH bonds is sensitive to the generation of hydrogen from NH bonds. Heat treatment leads to ordering of the films.

Chemical Composition of Boron Carbonitride Films Grown by Plasma-Enhanced Chemical Vapor Deposition from Trimethylamineborane

Boron carbonitride and boron nitride films were grown by plasma-enhanced chemical vapor deposition using trimethylamineborane and its mixtures with ammonia, hydrogen, or helium. The effects of the starting-mixture composition and substrate temperature on the chemical composition of the deposits was studied by ellipsometry, scanning microscopy, IR spectroscopy, Raman scattering, and x-ray photoelectron spectroscopy. The results indicate that the initial composition of the gas mixture, the nature of the activation gas, and substrate temperature play a key role in determining the deposition kinetics and the physicochemical properties of the deposits. Depending on these process parameters, one can obtain h-BN, h-BN + B4C, or BCxNy films.

Nondestructive and Nonpreparative Chemical Nanometrology of Internal Material Interfaces at Tunable High Information Depths

Improvement in the performance of functional nanoscaled devices involves novel materials, more complex structures, and advanced technological processes. The transitions to heavier elements and to thicker layers restrict access to the chemical and physical characterization of the internal material interfaces. Conventional nondestructive characterization techniques such as X-ray photoelectron spectroscopy suffer from sensitivity and quantification restrictions whereas destructive techniques such as ion mass spectrometry may modify the chemical properties of internal interfaces. Thus, novel methods providing sufficient sensitivity, reliable quantification, and high information depths to reveal interfacial parameters are needed for R&D challenges on the nanoscale. Measurement strategies adapted to nanoscaled samples enable the combination of Near-Edge X-ray Absorption Fine Structure and Grazing Incidence X-ray Fluorescence to allow for chemical nanometrology of internal material interfaces. Their validation has been performed at nanolayered model structures consisting of a silicon substrate, a physically vapor deposited Ni metal layer, and, on top, a chemically vapor deposited B(x)C(y)N(z) light element layer.

Characterization of some trimethyl(organylamino)silanes—precursors for preparation of silicon carbonitride films

A series of aminosilanes has been synthesized by the reaction of carboxylic acid di(organyl)amides with trimethyliodsilane. A purification method providing an increase in the yield of end products to 82% has been developed. The identity of the products has been confirmed using an elemental analysis and IR, UV, and 1H NMR spectroscopy. The spectral characteristics of the synthesized aminosilanes have been determined. The temperature dependences of the saturated vapor pressure have been established, and the thermodynamic characteristics of the vaporization processes have been calculated. It has been demonstrated that the aminosilanes Me3SiNEt2, Me3SiNHAll, and Me3SiNHPh are heat resistant in the temperature range 296–452 K and have a vapor pressure sufficient for their use in the processes of chemical vapor deposition of a substance, so that they can be recommended as precursors for synthesis of silicon carbonitride films.

Speciation of BCxNy films grown by PECVD with trimethylborazine precursor

Films of BCxNy were produced in a plasma-enhanced chemical vapor deposition process using trimethylborazine as precursor and with H2, He, N2, and NH3, respectively, as auxiliary gas. These films deposited on Si(100) wafers or fused quartz glass substrates were characterized chemically by X-ray photoelectron spectroscopy and by synchrotron radiation-based total-reflection X-ray fluorescence combined with near-edge X-ray absorption fine structure. Independent of the auxiliary gas, the B–N bonds are dominating. Furthermore, B–C and N–C bonds were identified. Oxygen, present in the bulk (in contrast to the surface layer of some nanometers, where molecular oxygen and/or water are absorbed) as an impurity, is bonded to boron or to carbon, respectively. The relation of boron and nitrogen changes with the character of the auxiliary gas: cB/cN ≈ 4:3 (for H2 and He) and cB/cN ≈ 1 (for N2 or NH3). Furthermore, physical properties such as the refractive index and the optical band-gap energy were determined.

The structure study of thin boron and silicon carbonitride films by diffraction of synchrotron radiation

Abstract Crystalline structure and phase composition of thin boron and silicon carbonitride films were investigated using diffraction of synchrotron radiation (SR). These films were synthesized by RPECVD using nontraditional volatile precursors. The diffraction measurements were performed at the station “Anomalous Scattering”, existed at the second canal of colliding electron–positron beam accelerator VEPP-3 of the Siberian center of SR (Institute of Nuclear Physics of SB RAS, Novosibirsk, Russia). The formation of polycrystalline novel phase not coinciding with known phases of boron carbide and boron nitride was observed in boron carbonitride films by diffraction experiments. The boron carbonitride films are not a mixture of boron carbide and boron nitride phases. We propose that these films are probably BCN phase. The X-ray diffraction and RHEED investigations revealed fine crystals of hexagonal Si 3 N 4 phase in amorphous matrix of silicon carbonitride films.