C. Schwebel

Raman scattering and stress measurements in Si1−xGex layers epitaxially grown on Si(100) by ion‐beam sputter deposition

Si1−xGex thin films have been grown on silicon substrates by ion‐beam sputter deposition (IBSD). Film stress has been determined from the change in deflection curvature of the substrate after deposition and strain has been investigated by using Raman scattering spectroscopy. These properties have been studied as a function of different parameters: growth temperature, layer thickness, and annealing conditions. Raman and stress results are in close correspondence with regard to effects of deposition temperature. Si‐rich films (0≤x≤0.3) were compressively strained for all deposition temperatures. A compressive to tensile stress change was observed in the Ge‐rich alloys (x=0.6) when the growth temperature reached Tg ≊ 500 °C. In addition, the strain as a function of depth from the surface has been studied by changing the laser wavelength. The strain has been shown to increase from the surface to the interior of the film. The origin of the stress observed in IBSD films is discussed and we show that this stress...

Ion beam sputtering deposition of tungsten: energy and mass effects of primary ions

Abstract The present work reports a study on the dependence of the properties of ion beam sputter deposited (IBSD) tungsten on silicon upon energy and mass effects of primary ions. Properties of thin W films ( t = 100–3000 A ) such as morphology (SEM), microstructure (XRD), impurity content (RBS) and resistivity were investigated. XRD patterns exhibit only the bcc α-W whatever the experimental parameters. The use of xenon leads to the best electrical characteristics; in this case resistivity depends weakly on incident ion energy and its variation versus thickness is rather well described in terms of a grain boundary scattering mechanism, whereas layers obtained with argon exhibit higher resistivities, which strongly depend on ion energy. We show that back-scattered ions from the target can account for the observed argon content. The more efficient electron-scattering centers appear to be argon atoms embedded in the growing film. This explanation agrees fairly well with results we obtained for DC magnetron sputter deposition and post deposition 45 keV Ar+ implantation.

Epitaxial growth of single-crystal Si1−xGex on Si(100) by ion beam sputter deposition

The first results are reported on Si1−xGex epitaxial layers grown on Si(100) by ion beam sputter deposition in ultrahigh vacuum. Growth temperatures were varied from 300 to 700°C, for compositions in the range 0.05 < x < 0.5. The properties of the grown films, such as morphology and structure, were studied by scanning electron microscopy and reflection high-energy electron diffraction respectively. Results indicate good monocrystallinity for the entire range of deposition temperature used. For deposition temperatures over 300°C, the films have smooth surfaces for all compositions and thicknesses. The distorted lattice parameters of epitaxial Si0.7Ge0.3 layers were measured by double-crystal diffractometry and the tetragonal strain was calculated. Increasing deposition temperature results in strain relaxation. Layers 3000 A thick grown at 400°C still retain a larger strain than that measured in a similar layer grown by molecular beam epitaxy. All these results may show the effects of energetic bombardment on the growing film.

EFFECT OF GROWTH CONDITIONS ON THE STRUCTURAL PROPERTIES OF ION BEAM SPUTTER DEPOSITED SIGE EPILAYERS

Structural properties of Si1−xGex layers epitaxially grown on Si(100) by Ion Beam Sputter Deposition were studied as a function of growth temperature and film thickness. It was shown that the structure of defects strongly depends on the growth temperature, Tg. The dislocations cross grid which is observed at the SiGe/Si interface for layers grown at high (700 °C) Tg is missing in layers grown at low (≲550 °C) Tg, while a new type of defects parallel to {001} and {113} lattice planes appear at these temperatures. The optimal Tg for a Ge content of 20‐25 at. % was found to be close to 550‐625 °C. Surface roughness for all the growth temperatures was found to be less than that for such a ‘‘smooth’’ technique as MBE. Photoluminescence studies revealed, to the best of our knowledge for the first time, two peaks on the low energy side in the neighborhood of the Si(TO) peak of the epilayers. The evolution of the intensity of these peaks is strongly correlated with the dynamics of strain relaxation and can be att...

Structural disorder in SiGe films grown epitaxially on Si by ion beam sputter deposition

Abstract SiGe/Si heterostructures grown by ion beam sputter deposition were characterized by high-resolution X-ray diffraction and transmission electron microscopy. Agglomerates of point defects, formed under ion bombardment during growth, were observed in electron microscopy images. These specific defects resulted in structural disorder which could be described in terms of local fluctuations of interplanar distances. The averaged magnitudes of the fluctuations were derived from X-ray diffraction spectra using a novel simulation procedure based on the direct summation of scattered waves in imperfect heterostructures. This approach allowed us to characterize quantitatively the degree of the structural disorder, and to follow defect transformations as a function of growth and annealing temperatures.

Characterization of ion-beam-sputtered tungsten films on silicon

Abstract The present work reports a study of the dependence of the properties of ion-beam-sputtered tungsten on silicon upon deposition parameters, especially deposition temperature and nature of the working gas. The physical characteristics of W layers such as morphology (SEM), texture (RHEED) and resistivity were investigated. The thermal stability and the silicide formation were studied by means of in situ AES and ex situ RBS. When W was deposited on heated substrates, the metal could react and disilicide (WSi 2 ) could form at temperature as low as 450°C. The nature of the rare gas had a great influence on layer properties: roughness, density, room temperature resistivity, resistivity dependence on layer thickness and measurement temperature. Resistivities of layers grown with xenon exhibited rather normal behaviour, i.e. characteristic of electron-phonon scattering, whereas layers obtained with argon gave rise to abnormal results that revealed that these layers had a great defect concentration and were polluted with a rather large amount of argon. This rare gas contamination was independent of the deposition temperature. We believe that energetic particles, bombarding the deposit as it accumulates, produce defects in the W layer and induces the abnormal properties of the metal layers. These particles are generated by reflection of the primary ions on the target, and they are expected to be more numerous when the working gas is argon according to its very low atomic mass relative to tungsten.

Stress in Si1−xGex films prepared by ion sputtering: origin and relaxation

Abstract Si1−xGex thin films were grown on silicon substrates by ion beam sputter deposition (IBSD) in an ultrahigh vacuum system. The film stress was determined from the change in deflection curvature of the substrate after deposition and was studied as a function of different parameters: growth temperature, composition (0% ⩽ × ⩽ 60%) and annealing conditions. The stress is mostly compressive and greater than that observed in films prepared under similar deposition conditions by molecular beam epitaxy (MBE). We observed an additional contribution of about 1 GPa independent of the film composition and thickness. The evolution of stress upon post-growth annealing conditions was followed. A plot of ln(σ) as a function of 1/kTa reveals a thermally activated process. All samples (0% ⩽ × ⩽ 8%) yield a similar value for the activation energy (QSR=0.1−0.3 eV). This value is considerably lower than that obtained for epitaxial films deposited by MBE or LRP-CVD. We speculate that the stress observed in IBSD layers is due to the effect of bombardment of the growing film by energetic particles. Measurements by Rutherford backscattering spectrometry show that the concentration of rare gas (xenon) incorporated in the films is too low to account for the stress. However, it is found that backscattered ions and (or) sputtered atoms that strike the growing film may have energies large enough to displace atoms and lead to compressive strain. To support this model quantitatively, computer calculations were carried out using an advanced version of the Monte Carlo transport of ions in matter, TRIM.

Growth mode of Ge films on Si(100) substrate deposited by ion beam sputtering

Abstract Germanium thin films have been grown on silicon(100) substrates by ion beam sputter deposition (IBSD) in an ultrahigh vacuum system. The growth mode of the films as a function of the growth temperature and the ion incidence angle was investigated by in situ Auger electron spectrometry. The morphology of the film surface was examined by scanning electron microscopy. The effect of the deposition temperature on the interface roughness was investigated after selectively etching the Ge film. We have found that the growth mode of IBSD-Ge on silicon does not agree with a layer-by-layer growth. The decay of the Si signal as the growth proceeds may be interpreted in terms of either a Stransky-Krastanov growth mode with island formation after two-dimensional growth or Si segregation to the surface. We showed that IBSD leads to more abrupt interfaces than molecular beam epitaxy. This last result may be related to the energetic bombardment of the film during deposition. To support this model more quantitatively, computer calculations have been carried out by using an advanced version of the Monte Carlo “transport of ions in matter” code ( trim ).

Stress in Si1-xGex Films Prepared by Ion Beam Sputtering

Si1-xGex thin films have been grown on silicon substrates by Ion Beam Sputter Deposition (IBSD) in a UHV system. Film stress has been determined from the change in deflection curvature of the substrate after deposition and strain has been investigated by double-crystal X-ray diffractometry. This property has been studied as a function of growth temperature and composition (0≤x≤60%). The stress is mostly compressive and greater than that observed in MBE films prepared under similar deposition conditions and therefore cannot be explained by the lattice mismatch. The excess stress, due to the deposition technique, is discussed in terms of incorporation of rare gas and bombardment effects on the growing film.

Growth of Thin Films by Ion Beam Sputtering: Study of Rare Gas Incorporation

This paper reports the results on a study of rare-gas incorporation in films deposited by ion beam sputter deposition (IBSD). It has been observed that electrical properties of metallic and semiconductor films depend on the nature and concentration of rare gas trapped in the layers. The origin of this rare gas is discussed. Angular distributions of rare gas emitted from a sputtered target are shown.