SiN~-coatings have been deposited by reactive magnetron sputtering. Gas pressure and film thickne... more SiN~-coatings have been deposited by reactive magnetron sputtering. Gas pressure and film thickness have been varied. Scanning electron microsopic views of the cross sections show a columnar structure as well as polycrystalline films varying with deposition parameters. For quantitative comparisons of the film morphology an average column diameter has been used as a characteristic value obtained from T E M images. Similar results have been obtained by scanning tunneling microscope avoiding a large expenditure of preparation. Scanning tunneling microscopy is suitable for investigations of the fractal nature of top surface of thin films and to determine the height function of thin SiN~-coatings on silicon wafers directly. Computer simulations of sputter processes allow to discuss the evolution of microstructures qualitatively.
The applicability of models based on fractal geometry to characterize thin-film surfaces is inves... more The applicability of models based on fractal geometry to characterize thin-film surfaces is investigated. The fractal geometry of sputtered chromium nitride and silicon nitride thin film surfaces is described using Fourier profile analysis of scanning tunneling microscopy images and a box counting method. The CrN x -and SiN xcoatings were deposited on silicon wafers by reactive magnetron sputtering. The columnar structure of the amorphous silicon nitride varied with deposition similarly to the stucture of the polycrystalline chromium nitride films. For quantitative comparison of film morphology, an average column diameter has been used as a characteristic. The average column diameter increases with increasing gas pressure because of shadowing processes during deposition. The fractal dimension decreases with increasing pressure. Films with fine columnar structures are characterized by a larger fractal dimension than films with a coarse columnar structure. The fractal dimension determined by Fourier analysis is larger than the dimension calculated by the box counting method. The reason may be the limited pixel density of digitized images.
The fractal dimension of sputtered thin film surfaces was determined. Topography was measured usi... more The fractal dimension of sputtered thin film surfaces was determined. Topography was measured using scanning tunneling microscopy (STM) and atomic force microscopy (AFM). It can be shown that measuring conditions have an important influence on the topographic data and the obtained fractal dimension. This influence was investigated systematically. The results of STM-and AFM-measurements have been compared. The results for surfaces imaged with AFM give lower values for the fractal dimension than with STM. Measurements were carried out with a standard cantilever and so the data have been filtered. Dynamic behavior of the measuring system is influenced by scanning speed and loop gain factor. During measurement of topographic signal high scanning speed and low loop gain factor produce a low pass behavior and the fractal dimension will be varied. If there is a disturbance in addition to the topographic signal (e.g. a noise) we found power spectra with more than one linear part. The calculated fractal dimension especially depended on the density of measuring points in the profile. The experimental results were verified by calculated Weierstrass-Mandelbrot functions.
Nitrides of refractory metals are investigated as diffusion barriers for Cu metallization. The co... more Nitrides of refractory metals are investigated as diffusion barriers for Cu metallization. The composition, thermal stability and inter diffusion in layered systems are characterized by depth profile analysis. For the quantification of depth profiles determination of sensitivity factors is essential. For nitrogen and other light elements matrix specific standards are often not available and compound standards are used for calibration. We have investigated the systems Ta-N and Ta-Si-N and for comparison Cr-N by means of Auger electron spectrometry (AES) and glow discharge optical emission spectrometry (GDOES). A non-linear calibration curve for the N=Cr intensity ratio was observed with GDOES in the Cr-N-system, probably caused by selfabsorption of the Cr line.
The focus of the investigations presented is to evaluate local alterations caused by chloride ion... more The focus of the investigations presented is to evaluate local alterations caused by chloride ions affecting thin, magnetron-sputtered CrN layers. Scanning-probe microscopy and analysis techniques are used for this estimation. Thin CrN layers were deposited by reactive magnetron sputtering. They were investigated in electrochemical scanning tunnelling microscopy (EC STM) by cyclic voltammetry in 1 mol L(-1) NaCl. Simultaneously, the surface topography changes were recorded with STM. Above 100 mV the anodic oxidation leads to formation of chromium(III) hydroxide and at sample potentials above 350 mV oxidation of Cr(OH)(2) and Cr(OH)(3) towards chromium(VI) as a soluble chromate starts. Transpassive dissolution of the coating takes place above 900 mV. Yellow colour of the electrolyte is a visible sign for the formation of chromium(VI). Changes of the surface topography indicate the formation of surface layers at anodic potentials. At cathodic potentials increase in current is measured...
To represent the corrosion characteristics of thin hard material layers, CrN layers, which were m... more To represent the corrosion characteristics of thin hard material layers, CrN layers, which were magnetron sputtered, have been exposed to solutions with chloride or sulfate ions. The alterations of the layer surfaces were examined. Static immersion tests were carried out ex-situ in 1 mol L(-1) NaCl or 1 mol L(-1) Na(2)SO(4) solution over a period of 14 months. For in-situ measurements, the layers were inserted into the electrochemical cell of an EC STM as the working electrode. The sample potential was altered cyclically. At the same time, voltammograms were taken and the topography alteration was observed. Alterations in the surface structure were documented as hybrid information resulting from changes in topography and the chemical consistency or the thickness of the oxide layers. These modifications were demonstrated with scanning tunnelling spectroscopy before and after the treatment with solutions. Several chemical phases (initial state and oxide layers) were distinguished with...
Nitrides of refractory metals are investigated as diffusion barriers for Cu metallization. The co... more Nitrides of refractory metals are investigated as diffusion barriers for Cu metallization. The composition, thermal stability and inter diffusion in layered systems are characterized by depth profile analysis. For the quantification of depth profiles determination of sensitivity factors is essential. For nitrogen and other light elements matrix specific standards are often not available and compound standards are used for calibration. We have investigated the systems Ta-N and Ta-Si-N and for comparison Cr-N by means of Auger electron spectrometry (AES) and glow discharge optical emission spectrometry (GDOES). A non-linear calibration curve for the N=Cr intensity ratio was observed with GDOES in the Cr-N-system, probably caused by selfabsorption of the Cr line.
Reactively sputtered Ta-Si-N x barrier systems of different nitrogen content on copper were inves... more Reactively sputtered Ta-Si-N x barrier systems of different nitrogen content on copper were investigated by photoelectron spectroscopy (XPS, UPS) and scanning tunnelling microscopy (STM). The measured photoelectron spectra (excitation He-I) showed a clear dependence of the electron state density near the Fermi edge on the content of nitrogen. These results correlate with the I(U) characteristics of the STM measurements and the electrical conductivity of these layers. #
Mechanical stress in atomic-layer deposition (ALD)-Al 2 O 3 films was investigated at room temper... more Mechanical stress in atomic-layer deposition (ALD)-Al 2 O 3 films was investigated at room temperature and during thermal cycling up to 870 8C. The films were generally under tensile stress. Thicker films (25-60 nm) showed a sharp stress increase at about 780-790 8C. X-ray diffraction (XRD)-, X-ray reflectance (XRR)-and X-ray photoelectron spectroscopy (XPS)measurements indicate an irreversible phase transition from amorphous AlO(OH) to a mixture of different crystalline Al 2 O 3 -phases. Annealing at higher temperatures leads to a stress reduction as a result of diffusion and recovery processes. The stress behaviour of thinner films (<20 nm) during thermal cycling is quite different. Tensile stress increases with increasing temperature and decreases to nearly the same value during cooling down. The process is continuous and reversible. #
SiN~-coatings have been deposited by reactive magnetron sputtering. Gas pressure and film thickne... more SiN~-coatings have been deposited by reactive magnetron sputtering. Gas pressure and film thickness have been varied. Scanning electron microsopic views of the cross sections show a columnar structure as well as polycrystalline films varying with deposition parameters. For quantitative comparisons of the film morphology an average column diameter has been used as a characteristic value obtained from T E M images. Similar results have been obtained by scanning tunneling microscope avoiding a large expenditure of preparation. Scanning tunneling microscopy is suitable for investigations of the fractal nature of top surface of thin films and to determine the height function of thin SiN~-coatings on silicon wafers directly. Computer simulations of sputter processes allow to discuss the evolution of microstructures qualitatively.
The applicability of models based on fractal geometry to characterize thin-film surfaces is inves... more The applicability of models based on fractal geometry to characterize thin-film surfaces is investigated. The fractal geometry of sputtered chromium nitride and silicon nitride thin film surfaces is described using Fourier profile analysis of scanning tunneling microscopy images and a box counting method. The CrN x -and SiN xcoatings were deposited on silicon wafers by reactive magnetron sputtering. The columnar structure of the amorphous silicon nitride varied with deposition similarly to the stucture of the polycrystalline chromium nitride films. For quantitative comparison of film morphology, an average column diameter has been used as a characteristic. The average column diameter increases with increasing gas pressure because of shadowing processes during deposition. The fractal dimension decreases with increasing pressure. Films with fine columnar structures are characterized by a larger fractal dimension than films with a coarse columnar structure. The fractal dimension determined by Fourier analysis is larger than the dimension calculated by the box counting method. The reason may be the limited pixel density of digitized images.
The fractal dimension of sputtered thin film surfaces was determined. Topography was measured usi... more The fractal dimension of sputtered thin film surfaces was determined. Topography was measured using scanning tunneling microscopy (STM) and atomic force microscopy (AFM). It can be shown that measuring conditions have an important influence on the topographic data and the obtained fractal dimension. This influence was investigated systematically. The results of STM-and AFM-measurements have been compared. The results for surfaces imaged with AFM give lower values for the fractal dimension than with STM. Measurements were carried out with a standard cantilever and so the data have been filtered. Dynamic behavior of the measuring system is influenced by scanning speed and loop gain factor. During measurement of topographic signal high scanning speed and low loop gain factor produce a low pass behavior and the fractal dimension will be varied. If there is a disturbance in addition to the topographic signal (e.g. a noise) we found power spectra with more than one linear part. The calculated fractal dimension especially depended on the density of measuring points in the profile. The experimental results were verified by calculated Weierstrass-Mandelbrot functions.
Nitrides of refractory metals are investigated as diffusion barriers for Cu metallization. The co... more Nitrides of refractory metals are investigated as diffusion barriers for Cu metallization. The composition, thermal stability and inter diffusion in layered systems are characterized by depth profile analysis. For the quantification of depth profiles determination of sensitivity factors is essential. For nitrogen and other light elements matrix specific standards are often not available and compound standards are used for calibration. We have investigated the systems Ta-N and Ta-Si-N and for comparison Cr-N by means of Auger electron spectrometry (AES) and glow discharge optical emission spectrometry (GDOES). A non-linear calibration curve for the N=Cr intensity ratio was observed with GDOES in the Cr-N-system, probably caused by selfabsorption of the Cr line.
The focus of the investigations presented is to evaluate local alterations caused by chloride ion... more The focus of the investigations presented is to evaluate local alterations caused by chloride ions affecting thin, magnetron-sputtered CrN layers. Scanning-probe microscopy and analysis techniques are used for this estimation. Thin CrN layers were deposited by reactive magnetron sputtering. They were investigated in electrochemical scanning tunnelling microscopy (EC STM) by cyclic voltammetry in 1 mol L(-1) NaCl. Simultaneously, the surface topography changes were recorded with STM. Above 100 mV the anodic oxidation leads to formation of chromium(III) hydroxide and at sample potentials above 350 mV oxidation of Cr(OH)(2) and Cr(OH)(3) towards chromium(VI) as a soluble chromate starts. Transpassive dissolution of the coating takes place above 900 mV. Yellow colour of the electrolyte is a visible sign for the formation of chromium(VI). Changes of the surface topography indicate the formation of surface layers at anodic potentials. At cathodic potentials increase in current is measured...
To represent the corrosion characteristics of thin hard material layers, CrN layers, which were m... more To represent the corrosion characteristics of thin hard material layers, CrN layers, which were magnetron sputtered, have been exposed to solutions with chloride or sulfate ions. The alterations of the layer surfaces were examined. Static immersion tests were carried out ex-situ in 1 mol L(-1) NaCl or 1 mol L(-1) Na(2)SO(4) solution over a period of 14 months. For in-situ measurements, the layers were inserted into the electrochemical cell of an EC STM as the working electrode. The sample potential was altered cyclically. At the same time, voltammograms were taken and the topography alteration was observed. Alterations in the surface structure were documented as hybrid information resulting from changes in topography and the chemical consistency or the thickness of the oxide layers. These modifications were demonstrated with scanning tunnelling spectroscopy before and after the treatment with solutions. Several chemical phases (initial state and oxide layers) were distinguished with...
Nitrides of refractory metals are investigated as diffusion barriers for Cu metallization. The co... more Nitrides of refractory metals are investigated as diffusion barriers for Cu metallization. The composition, thermal stability and inter diffusion in layered systems are characterized by depth profile analysis. For the quantification of depth profiles determination of sensitivity factors is essential. For nitrogen and other light elements matrix specific standards are often not available and compound standards are used for calibration. We have investigated the systems Ta-N and Ta-Si-N and for comparison Cr-N by means of Auger electron spectrometry (AES) and glow discharge optical emission spectrometry (GDOES). A non-linear calibration curve for the N=Cr intensity ratio was observed with GDOES in the Cr-N-system, probably caused by selfabsorption of the Cr line.
Reactively sputtered Ta-Si-N x barrier systems of different nitrogen content on copper were inves... more Reactively sputtered Ta-Si-N x barrier systems of different nitrogen content on copper were investigated by photoelectron spectroscopy (XPS, UPS) and scanning tunnelling microscopy (STM). The measured photoelectron spectra (excitation He-I) showed a clear dependence of the electron state density near the Fermi edge on the content of nitrogen. These results correlate with the I(U) characteristics of the STM measurements and the electrical conductivity of these layers. #
Mechanical stress in atomic-layer deposition (ALD)-Al 2 O 3 films was investigated at room temper... more Mechanical stress in atomic-layer deposition (ALD)-Al 2 O 3 films was investigated at room temperature and during thermal cycling up to 870 8C. The films were generally under tensile stress. Thicker films (25-60 nm) showed a sharp stress increase at about 780-790 8C. X-ray diffraction (XRD)-, X-ray reflectance (XRR)-and X-ray photoelectron spectroscopy (XPS)measurements indicate an irreversible phase transition from amorphous AlO(OH) to a mixture of different crystalline Al 2 O 3 -phases. Annealing at higher temperatures leads to a stress reduction as a result of diffusion and recovery processes. The stress behaviour of thinner films (<20 nm) during thermal cycling is quite different. Tensile stress increases with increasing temperature and decreases to nearly the same value during cooling down. The process is continuous and reversible. #
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Papers by Wieland Zahn