G. Erdélyi

University of Debrecen, Debrecen, Hajdu-Bihar, Hungary

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Publications (25)8.74 Total impact

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    ABSTRACT: Low temperature analysis of diffusion and intermixing of Co–Si systems are very important in applications for microelectronics and Ultra Large Scale Integration (ULSI). In this communication a comprehensive report has been given on degradation and diffusion processes in the Si(substrate)/Co(150 nm)/Ta(10 nm) system. The samples were prepared by DC magnetron sputtering and were annealed in argon ambient at several temperatures ranging from 400 to 623 K for various times. The composition of the samples was investigated by Secondary Neutral Mass Spectrometry (SNMS). The degradation/intermixing starts with fast (grain boundary (GB)) diffusion of the Si into the Co layer. After some incubation time Si atoms appear and spread over the Co/Ta interface. This amount of Si accumulated at the Co/Ta interface acts as a reservoir for back-diffusion into the Co layer from the Co/Ta interface through the slower grain boundaries. At higher temperatures the formation of a Co–Si phase was detected at the Co/Si and Co/Ta interface. Three different diffusion coefficients were calculated from the SNMS concentration–depth profiles using “Central-gradient” (CG) and “First-appearance” methods. The observed intermixing was interpreted as a mixture of different “C-type” grain boundary diffusion processes. Furthermore, the experimental results are also compared with computer simulations modelling the grain-boundary diffusion through different grain-boundary paths. From the SNMS profiles measured at different temperatures the activation energy of the GB interdiffusion coefficients was deduced using the “CG method”.
    Vacuum. 01/2012; 86(6):724-728.
  • Defect and Diffusion Forum 01/2011; 312-315:1208-1215.
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    ABSTRACT: The effect of hydrostatic pressure on photo-induced surface expansion in As0.2Se0.8 thin films has been studied in the pressure range of 0–0.5GPa. The development of the surface relief was investigated at different intensities and exposure of laser irradiation. We have observed that the applied pressure suppressed the rate of the surface relief formation, therefore the pressure dependent components of the structural transformations in glasses should be included to the model of this phenomenon.
    Journal of Non-Crystalline Solids 01/2011; 357(11):2349-2351. · 1.60 Impact Factor
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    ABSTRACT: Proper understanding of the degradation mechanisms and diffusion kinetics of copper and cobalt interconnections for advanced microelectronics is important from the point of view of fundamental research and technology as well. In this paper Si(substrate)/Ta(10nm)/Cu(25nm)/W(10nm) and Si(substrate)/Co(150nm)/Ta(10nm) samples, prepared by DC magnetron sputtering, were in investigated. The samples were annealed at several temperatures ranging from 423K to 823K for various times. The composition distributions were detected by means of Secondary Neutral Mass Spectrometry (SNMS). Microstructural characterization of samples was carried out by means of Transmission Electron Microscopy (TEM). It is shown that the changes in the composition profiles were mainly caused by grain boundary, GB, diffusion and the effective GB diffusion coefficients of Ta in Cu were determined both by the “first appearance” and “centre-gradient” methods. The activation energy is 100kJ/mol. The importance of the Ta penetration into the Cu and its accumulation at the Cu/W interface can lead to an increase of the Ta content in the copper film. This can be an important factor in the change/degradation of the physical parameters (e.g. the electrical resistance) of interconnects. Furthermore a Ta segregation factor in Cu was evaluated. Preliminary results in the Si(substrate)/Co(150nm)/Ta(10nm) indicate fast (GB) diffusion of the Si into the Co layer, formation of a cobalt silicide layer at the Co/Si interface and Si accumulation first at the Ta/Co interface and later a retarded accumulation at the free Ta surface.
    Vacuum. 01/2010; 84(7):953-957.
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    ABSTRACT: Proper understanding of the degradation mechanisms and diffusion kinetics of copper and cobalt interconnections for advanced microelectronics is important from the point of view of fundamental research and technology as well. In this paper Si(substrate)/Ta(10 nm)/Cu(25 nm)/W(10 nm) and Si(substrate)/Co(150 nm)/Ta(10 nm) samples, prepared by DC magnetron sputtering, were in investigated. The samples were annealed at several temperatures ranging from 423 K to 823 K for various times. The composition distributions were detected by means of Secondary Neutral Mass Spectrometry (SNMS). Microstructural characterization of samples was carried out by means of Transmission Electron Microscopy (TEM). It is shown that the changes in the composition profiles were mainly caused by grain boundary, GB, diffusion and the effective GB diffusion coefficients of Ta in Cu were determined both by the “first appearance” and “centre-gradient” methods. The activation energy is 100 kJ/mol. The importance of the Ta penetration into the Cu and its accumulation at the Cu/W interface can lead to an increase of the Ta content in the copper film. This can be an important factor in the change/degradation of the physical parameters (e.g. the electrical resistance) of interconnects. Furthermore a Ta segregation factor in Cu was evaluated. Preliminary results in the Si(substrate)/Co(150 nm)/Ta(10 nm) indicate fast (GB) diffusion of the Si into the Co layer, formation of a cobalt silicide layer at the Co/Si interface and Si accumulation first at the Ta/Co interface and later a retarded accumulation at the free Ta surface.
    Vacuum. 01/2010; 85(4):493-497.
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    ABSTRACT: One of the most important processes in Cu metallization for highly integrated circuits is to fabricate reliable diffusion barriers. Recently, thin films made of refractory metals and their compounds have been widely used in solid-state electronics as barriers because of their good electric properties, favourable thermal properties and chemical stability. Thermal stability of Tantalum (Ta) and Tantalum-oxide (TaOx) layers as a diffusion barrier in Si/Ta/Cu, Si/TaOx/Cu and Si/Ta-TaOx/Cu systems have been investigated. Si/Ta (10 nm)/Cu (25 nm)/W (10 nm), Si/TaOx (10 nm)/Cu (25 nm)/W (10 nm) and Si/Ta (5 nm)TaOx (5 nm)/Cu (25 nm)/W (10 nm) thin layers were prepared by DC magnetron sputtering. A tungsten cap layer was applied to prevent the oxidation of the samples during the annealing process. The samples were annealed at various temperatures (473 K–973 K) in vacuum. Transmission Electron Microscopy, X-ray diffraction, X-Ray Photoelectron Spectroscopy and Secondary Neutral Mass Spectrometry were used to characterize the microstructure and diffusion properties of the thin films. Our results show that at the beginning phase of the degradation of the Si/Ta/Cu system Ta atoms migrate through the copper film to the W/Cu interface. In the Si/TaOx/Cu system the crystallization of TaO and the diffusion of Si through the barrier determine the thermal stability. The Ta–TaO bilayer proved to be an excellent barrier layer between the Si and Cu films up to 1023 K. The observed outstanding performance of the combined film is explained by the continuous oxidation of Ta film in the TaOx–Ta bilayer.
    Vacuum. 08/2009;
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    ABSTRACT: Thermal annealing of Si/Si1-xSbx/Si amorphous thin film tri-layer samples (x=18 and 24 at%Sb) under 100 bar Ar pressure results in an interesting pattern formation. In pictures, taken by means of cross-sectional transmission electron microscopy (TEM), stripe-shaped contrast, with three maxima, parallel with the interfaces can be seen. Secondary neutral mass spectrometer (SNMS) measurements revealed that the regions with different contrasts correspond to Sb-rich and Sb-depleted regions. Furthermore, the Sb concentration peaks in the Sb-rich regions, especially at longer annealing times, are different: the peak developed at the Si/SiSb interface closer to the free surface decays faster than that of the inner one closer to the substrate. The pattern formation is interpreted by segregation-initiated spinodal-like decomposition, while the difference of the Sb concentration peaks is explained by the resultant Sb transport to and evaporation from the free surface. The possible role of formation of nanocrystalline grains, in the explanation of the fast transport under pressure as compared to vacuum is also discussed.
    03/2009;
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    ABSTRACT: Amorphous silicon materials and its alloys become extensively used in some technical applications involving large area of the microelectronic and optoelectronic devices. However, the amorphous-crystalline transition, segregation and diffusion processes still have numerous unanswered questions. In this work we study the Sb diffusion into an amorphous Si film by means of Secondary Neutral Mass Spectrometry (SNMS). Amorphous Si/Si1-xSbx/Si tri-layer samples with 5 at% antimony concentration were prepared by DC magnetron sputtering onto Si substrate at room temperature. Annealing of the samples were performed at different temperature in vacuum (p<10-7 mbar) and 100 bar high purity (99.999%) Ar pressure. During annealing a rather slow mixing between the Sb-alloyed and the amorphous Si layers was observed. Supposing concentration independent diffusion, the evaluated diffusion coefficients are in the range of ~10-21 m2s-1 at 823 K.
    03/2009;
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    ABSTRACT: CONF_NAME: Book of abstracts of 4-th Symposium on Vacuum based Science and Technology in conjunction with 8-th Annual Meeting of German Vacuum Society., CONF_PLACE: Kolobrzeg, Lengyelország
    01/2009: pages 44;
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    ABSTRACT: CONF_NAME: International Workshop Diffusion and Solid State Reactions on Nanoscale, CONF_PLACE: Debrecen, Magyarország
    01/2009: pages 23;
  • G. Erdélyi, Cs. Guthy, D. L. Beke
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    ABSTRACT: The pressure dependence of point-defect concentrations is calculated on the basis of two recently published models. It is demonstrated that the effective formation volume of vacancies shows asymmetrical character about stoichiometry. For Ni-rich and stoichiometric compositions, the concentration of Ni vacancies versus pressure can be described by a simple exponential function. The concentration of Ni antisite defects is independent of pressure. For Al-rich compositions, the concentration of Ni vacancies shows a more complex behaviour. At low pressures the vacancy concentration is independent of pressure, the effective formation volume is zero, while above a critical pressure the vacancy concentration becomes pressure dependent. This can be explained by the annihilation reaction of Ni vacancies. The pressure of complete replacement depends on the stoichiometry and has proved to be very sensitive to the input parameters used in the different models. The changes expected in diffusion activation energy and activation volume with composition are discussed on the basis of calculated temperature and pressure dependence of Ni vacancy concentration, assuming vacancy-mediated diffusion. The pressure effect on the boundary that separates regions in which triple defects or interbranch defects dominate was also investigated. It was observed that pressure expands the region in which Al interbranch defects dominate.
    Philosophical Magazine A 05/2003; 83(1):109-123.
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    ABSTRACT: The crystallization of amorphous SiSb mono-, Si/SiSb/Si tri- and Si/SiSb multilayers, carried out at 883 K under different hydrostatic pressures has been investigated by cross-sectional transmission electron microscopy (TEM). After annealing crystallization of the amorphous SiSb layer was observed, while the pure Si layer remained amorphous. It was observed that hydrostatic pressure and the initial Sb concentration enhance crystallization and decomposition processes.In the case of the Si/SiSb/Si trilayer films, the nanocrystalline SiSb layer underwent a spinodal-like decomposition resulting in straight stripes parallel to the surface.
    Vacuum. 01/2003;
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    ABSTRACT: Radio-tracer diffusion measurements of 63Ni have been performed in Ni75AlxGe25−x ternary intermetallic compounds at various temperatures. The tracer diffusivity was found to depend exponentially on the Ge content of the alloy. These compounds are ordered with the L12 structure, where the Ni atom diffusion proceeds mainly via Ni sublattice site jumps. The change of the diffusivity can be attributed to the change in vacancy concentration on the Ni sublattice as well as to the composition dependence of the saddle-point energy of the diffusion jumps.
    Intermetallics 01/2002; 10(9):887-892. · 1.86 Impact Factor
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    ABSTRACT: The volume diffusion of Ni was studied in a nearly equiatomic B2 NiTi compound at 1285 K in the pressure range of 0–0.91 GPa. Our measurements, carried out by the tracer technique, proved that the volume diffusion coefficient is independent of the external pressure, and the evaluated activation volume is close to zero. Results may refer either to the interstitial diffusion mechanism or vacancy-mediated diffusion, indicating that in the latter case the vacancy concentration is pressure independent in the investigated pressure range.
    Physical review. B, Condensed matter 10/2000; 62(17).
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    ABSTRACT: mbar were investigated by means of Auger electron spectroscopy in the temperature range 893–978K. Measuring the time dependence of the normalized Auger intensity of Cu, we concluded that the process is controlled by asurface reaction at the perimeters of beads. From the temperature dependence of the initial and final parts of these curves we were able to determine the energy of activation of the desorption of Cu and of the surface reaction as well.
    Applied Physics A 12/1997; 66(1):93-98. · 1.55 Impact Factor
  • Defect and Diffusion Forum 01/1997;
  • Solid State Phenomena. 01/1997; 56:181-182.
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    ABSTRACT: Morphological changes of beaded Ag film on sapphire and on alumina scale were investigated by means of scanning electron microscopy and Auger spectroscopy in the temperature range of 822–973 K. It was found that the decrease of the effective thickness and the shift of the boundary of the layer can be attributed to the evaporation of silver into the gas phase. Experimental results were analyzed in terms of the model developed by Kaganovskii and Beke. Our results show that the process is controlled by surface diffusion and temperature dependence of the surface mass transport coefficients is deduced from the experimental data. © 1996 American Institute of Physics.
    Journal of Applied Physics 09/1996; · 2.21 Impact Factor
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    ABSTRACT: The structures of symmetrical <111> tilt boundaries, formed in a two-dimensional array of steel balls placed (between two glass-sheets) into an alternating magnetic field, were investigated. It was observed that coincidence Σ13, Σ39, Σ7, Σ19, and Σ37 boundaries were more or less ordered and their structure can be composed of mixtures of two (slightly distorted) structural units. Different defects (e.g. volume and grain-boundary dislocations, steps, faceting) can also be observed ; their presence caused difficulties in identification of the periodicity in boundaries investigated. It was shown for an asymmetrical Σ7 boundary that energetically a curved boundary was more favourable than a plane one. Having increased the intensity of the magnetic field the dynamic properties of grain-boundaries (grain-boundary migration, diffusion) can also be visualized by a videotape-recording.
    http://dx.doi.org/10.1051/jphyscol:1990150. 01/1990;
  • Philosophical Magazine A 11/1987; 56(5):673-680.