K. G. Grigorov

Aluminium diffusion in titanium nitride films. Efficiency of TiN barrier layers

Two kinds of reactively evaporated titanium nitride films with columnar (B0 films) and fine-grained (B+ films) film structures, respectively, have been examined as diffusion barriers for preventing aluminium diffusion. The aluminium diffusion profiles have been investigated by 2 MeV 4He+ Rutherford backscattering spectrometry (RBS) at temperatures up to 550° C. The diffusivity from 300° C to 550° C is: D[m2s−1]=3×10−18 exp[−30/(RT)] in B0 layers and D[m2s−1]=1.4×10−16 exp[−48/(RT)] in B+ TiN layers. The activation-energy values determined indicate a grain boundary diffusion mechanism. The difference between the diffusion values is determined implicitly by the microstructure of the layers. Thus, the porous B0 layers contain a considerable amount of oxygen absorbed in the intercolumnar voids and distributed throughout the film thickness. As found by AES depth profiling, this oxygen supply allows the formation of Al2O3 during annealing the latter preventing the subsequent diffusion of the aluminium atoms.

Diffusion of silicon in titanium nitride films. Efficiency of TiN barrier layers

Two kinds of reactively evaporated titanium nitride films with columnar (B0 films) and fine-grained film structure (B+ films) have been examined as diffusion barriers, preventing the silicon diffusion in silicon devices. The silicon diffusion profiles have been investigated by 2 MeV 4He+ Rutherford backscattering spectrometry (RBS) after annealing at temperatures up to 900° C, in view of application of high-temperature processes. The diffusivity from 400 to 900° C: D (m2 s−1)=2.5×10−18 exp[−31 kJ/mol/(RT)] in B0 layers and D (m2 s−1)=3×10−19 exp[−26 kJ/mol/(RT) in B+ TiN layers. The diffusivities determined correspond to grain boundary diffusion, the difference being due to the different microstructure. The very low diffusivity of silicon in B+ TiN layer makes it an excellent high-temperature barrier preventing silicon diffusion.

SYNTHESIS AND CHARACTERIZATION OF CONDUCTIVE TITANIUM MONOXIDE FILMS. DIFFUSION OF SILICON IN TITANIUM MONOXIDE FILMS

Abstract Titanium monoxide films of about 100 μm thickness have been deposited onto Si (100) by reactive ion beam deposition. The established experimental conditions provided reproducibility of synthesised films. With a fcc cubic structure and a lattice parameter of 4.17A, as found by X-ray diffraction ; this lattice value corresponded to an oxygen content of about 52%. The composition was confirmed by Auger electron spectroscopy based on the O-KLL\Ti-LMM integral ratio and on the observation of the fine features of the Ti-LMM peaks. The films were electrically conducting with a resistivity of 170 μΩ cm−1. The low diffusivity of Si in TiO films, as estimated by RBS analysis, offers potential application in microelectronics of the conductive oxide form.

XPS study of Au/GaN and Pt/GaN contacts

Au/GaN and Pt/GaN contacts have been studied with XPS. According to XPS depth profiling, the N signal is weak in the region below the metal contact and the Pt or Au signal decreases much more slowly than expected for a sharp interface. Next, we have performed in situ studies of the formation of Au contacts on GaN. In contrast to the results from depth profiling, we observe 2D growth and little or no chemical interaction between Au and GaN. This suggests that conventional calculations of sputtering yields and ion-beam-induced mixing cannot be applied to the analysis of noble metal/GaN depth profiles. Heating during or after Au deposition results in strong clustering, observed by both XPS and AFM. The Schottky barrier height measured by XPS is 1.15 eV.

Iron diffusion from pure Fe substrate into TiN buffer layers

Abstract The diffusivity of iron in TiN films has been determined in samples prepared by reactive evaporation of Ti in N 2 atmosphere on silicon substrates followed by evaporation of pure iron. The iron diffusion profiles have been investigated by 2 MeV 4 He + Rutherford backscattering spectroscopy (RBS) after annealing at temperatures up to 600°C. The diffusivity from 200°C to 600°C, D [m 2 /s] = 1.4 × 10 −15 exp[−46/( RT )] is rather high when compared to the diffusivity of other atom species, as for example Si and Al, in TiN films.

Hollow cathode magnetron deposition of AlN thin films: crystalline structure and morphology

A new dc hollow cathode plasma source has been assembled whith a conventional planar magnetron cathode used together with another plane cathode plate to form a hollow cathode cavity. The system comprises two cathode plates of aluminium separated by a distance d, one of them acting as target of the magnetron cathode, the other being an ordinary plate. The discharge anode is a metallic flange of the vacuum chamber. This leads to enhanced ionization in the cathode cavity region and enables the discharge to operate at significantly lower pressures than for a typical planar magnetron configuration. As a consequence, sputtered atoms can reach a substrate with minimum energy loss due to collisions with filling gas atoms. The discharge gas was a mixture of argon and nitrogen. AlN thin films were grown on silicon substrates, at ambient temperature, and characterized with respect to the structure and morphology by XRD and AFM analyses respectively. The structure and roughness of the AlN films were studied as a function of the deposition parameters.

A simple estimate of deposited energy and concentration profiles in films produced by Ion-Assisted Physical Vapour Deposition

Analytical expressions for estimating the energy dissipation and the film constituent concentration profiles in films grown by Ion-Assisted Physical Vapour Deposition (IA PVD) are given. Two cases of IA PVD are considered: ion-assistance performed by inert-gas ions as well as by ions of a film constituent. As an example of application, concentration and damage depth profiles in h-BN films grown by IA PVD are calculated and a comparison is made with results obtained by computer simulation.

Structural and Magnetic Properties of Nanosized Barium Hexaferrite Powders Obtained by Microemulsion Technique

Thin hexagonal barium hexaferrite particles synthesized using the microemulsion technique were studied. A water-in-oil reverse microemulsion system with cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, n-butanol as a co-surfactant, n-hexanol as a continuous oil phase, and an aqueous phase were used. The microstructural and magnetic properties were investigated. The particles obtained were mono-domain with average particle size 280 nm. The magnetic properties of the powder were investigated at 4.2 K and at room temperature. The saturation magnetization was 48.86 emu/g and the coercivity, 2.4 x 105 A/m at room temperature. The anisotropy field Ha and magneto-crystalline anisotropy K1 were 1.4 x 106 A/m and 2.37 x 105 J/m3, respectively.

Ion-induced densification of pvd films—a choice of the optimum density of ion bombardment

The densification process by ion-assisted physical vapour deposition of films is considered as a consequence of rearrangement of atoms in the near-surface film layer. A model is proposed allowing the quantitative estimate of the optimum ion current density required to produce a film with maximum density.

Surface modification of EPDM rubber by microwave excited plasmas

Abstract In the present work, a microwave excited plasma (2·45 GHz, 1 kW) was used to modify the surface characteristics of the ethylene propylene diene monomer rubber. The samples were treated with a mixture of nitrogen, hydrogen and argon plasmas. The operating gas pressure was in the 0·2–1 Torr range, the gas flowrate between 5 and 100 sccm and the treatment time varied from 10 to 600 s. The influence of the plasma treatment on the superficial characteristics of the samples was analysed by contact angle measurements and atomic force microscopy. The results show that the plasma treatment can promote an important decrease in the contact angle from 101° for untreated sample to 34° for samples treated in a mixture of H2/N2/Ar for 2 min, which corresponds an increase on the rubber surface adhesion work from 59 to 133 mJ m−2.