Papers by Keyword: Multilayer

Abstract: Semiconductor component and microelectromechanical system manufacturing requires metal patterning in an integrated circuit (IC), using the photoresist lift-Off process. Ideal advantages like cost-effectiveness, reduction of complexity and process maturity are associated with the lift-Off process. Alternatively, the choice of photoresist relies on factors such as cost, initial photoresist thickness and reliable processing parameters extraction. However, the availability of the cheap photoresist is still at question. For the case of the underlying study, a highly cheap photoresist E8015 of thickness 38-micrometer was developed for the purpose of edge profiling. Desirable extraction of the useful parameter range for dry resist processing is performed. Parameter variation like exposure energy and development time led to a successful undercut angle of 66° to 73°, while the straight edge profile of 90° was realized at various parameter combinations. Eventually, a metallic multilayer of 10-micrometer thickness is successfully lifted off on plain silicon. Controlled self-propagating reaction within these structured metallic layers may be employed for IC packaging hereafter.

Abstract: The effect of layer thickness on hardness and buckling behavior was investigated on Ni-Co-Cu/Cu multilayered films. The Ni-Co-Cu/Cu multilayered films were grown on annealed copper substrates by electrodeposition. We fabricated the multilayered films with various layer thicknesses ranging from 10 nm to 1000 nm. First, dependence of Vickers hardness on the Cu layer thickness was investigated. When the Ni-Co-Cu layer had the constant thickness of 75 nm and the Cu layer thickness was smaller than 75 nm, the hardness increased rapidly with decreasing Cu layer thickness. Subsequently, compressive tests were conducted on the multilayered films having the component layers ranging from100 nm to 1000 nm, where the hardness values did not change rapidly with layer thickness. The copper substrates coated with the multilayered films were compressed until 20% strain. From SEM surface observations after the compressive tests, formations of band-like structures having a certain thickness were recognized. Cross-sectional observation revealed that some band-like structures were formed as a result of local buckling of the multilayered film. The vertical thickness of the bank-like structures increased linearly with increasing component layer thickness.

Abstract: In magnetoelectric sensors for the detection of weak magnetic fields, the magnetostrictivecomponent is required to show a high strain at small magnetic field changes. Co-Fe alloys, amongrare earth free materials, have one of the largest saturation magnetostriction and are magnetically softat the same time. In this study, Co-Fe alloy films with 66 at.-% Co are prepared by magnetron sputterdeposition of Co/Fe-multilayers which differ in their individual layer structure and in a subsequentrapid thermal annealing process. The influence of the initial bilayer period and the annealing temperatureon the phase formation and film structure are investigated. X-ray diffraction revealed a higherfraction of the desired face-centered cubic solid solution for thicker individual layers after the 800 °Cannealing. The change of the electrical in-plane resistivity reaches a minimum around 500 °C and iscorrelating well with the observed grain growth and solid solution phase formation. The investigationof magnetic properties with vibrating sample magnetometry shows coercive fields of 3.2 kA/m and2.2 kA/m for fully alloyed films with initial bilayer periods of 25 nm and 250 nm, respectively.

Abstract: Influence of gamma irradiation to the magneto-impedance ratio of the electrodeposited [NiFe/Cu]₄ multilayer on meander-shape PCB substrate has been studied. The magneto-impedance ratios were measured for both un-irradiated and irradiated by gamma radiation of Co-60 with a total dose of 40 Gy. The morphological structure were done by using scanning electron microscopy (SEM). The decrease in grain size of the samples after Gamma irradiated is observed. The magnetic property modifies as consequence of the change in the microstructure samples. Within result, the magneto-impedance ratio decreases around 34.9% for irradiated sample.

Abstract: This study presents a real-time method for determining the thickness of each layer in multilayer thin films. Artificial neural networks (ANNs) were introduced to estimate thicknesses from a transmittance spectrum. After training via theoretical spectra which were generated by thin-film optics and modified by noise, ANNs were applied to estimate the thicknesses of four-layer nanoscale films which were TiO₂, Ag, Ti, and TiO₂ thin films assembled sequentially on polyethylene terephthalate (PET) substrates. The results reveal that the mean squared error of the estimation is 2.6 nm², and is accurate enough to monitor film growth in real time.

Abstract: To reduce maintenance and to increase the corrosion protection and lifetime of maritimestructures while complying with environmental standards, multilayer coatings are applied to protectsteel sections. A new generation of hybrid sol-gel and/or HiPIMS Ni-based thin films appear toconstitute an efficient pre-treatment before the anti-corrosion paint application. However, increasingthe number of coatings and associated interfaces may lead to coating failure due to stresses inducedby the different deposition processes. Therefore developing smart models to assess the stressdistribution along these multilayers appears of significant importance. The well-known Stoneyformula cannot be used for multilayers and owing to the large dimensions of the object to be protected.To assess an easily measurable curvature after deposition, thin steel sheets are used but do not respectany more the Stoney hypotheses. So we set up an analytical thermo-elasto-plastic model to evaluatethe stresses induced by depositions in each layer. This model is based on the various thermalexpansion coefficients of every coat. After extrapolation along the complete thickness, combiningsol-gel and PVD deposition smoothens the stress difference between steel and paint. The shearstresses at interface seems thus to be reduced. The evolution of the stress difference between layerswith the imposed deflection can predict the mechanical strength and the interface failure. In order toevaluate the quality of the model, in-situ four-point bending in SEM was performed to study of theadhesion between the various layers. The results deduced from the model are in good agreement withSEM images.

Abstract: Steel tools, which are used in industrial high-throughput processes like injection molding, are susceptible for wear and corrosion due to rapid cyclic temperature and pressure fluctuation as well as the use of abrasive polymers. For the protection of tool surfaces high quality ceramic thin films can be applied by metal-organic chemical vapor deposition (MOCVD). In addition to protective properties ceramic materials like yttria-stabilized zirconia (YSZ) are able to thermally insulate tool surfaces providing a more precise temperature regulation with intent to avoid the formation of surface flaws, e.g. weld lines, in the later plastic parts. At the same time it enables the shortening of cycle times as well as the decrease of energy demands during the molding process. In this work we demonstrate the fabrication of zirconia based thin films and multilayer systems on steel tools with complex 3D surfaces via MOCVD using metal acetylacetonates as precursor materials. Coating development was carried out by measuring the film thicknesses at different parameter settings. The usage of autonomous liquid flow controllers enables the formation of multilayer systems as well as the control of crystallinity by addition of different dopants to the material. For process development substrates were engineered according to tool geometry containing typical cavities and defined cracks with aspect ratios up to 1:60. That application enables the proof of conformity and the verification of homogeneous film thickness distribution. Exploitation of these results offers the coating of tools, which are tested regarding their desired properties by industrial project partners under production conditions.

Abstract: The cubic-NbN/NbCN multilayers with modulation periodicity (Λ) ranging from 4.2 to 39.1 nm were deposited on Si (100) substrate by reactive magnetron sputtering in a mixture of Ar and N₂ gases. The Λ dependent structural, mechanical and tribological properties for resulting c-NbN/NbCN multilayers were explored. As Λ varied from 4.2 to 39.1 nm, all the films exhibited an obvious modulated structure. Increasing the Λ, the Nb (C,N)(111) peak in XRD gradually shifted to bigger angles and the peak intensity of NbN(111) became stronger. The stress for all multilayers was compressive ranging in between the stress for both NbN and NbCN single layers, and the stress value was stable with increasing Λ. The NbN layer was beneficial to relaxing the compressive stress which induced by NbCN layer. In addition, as Λ increases, the hardness (H) first increased, and then decreased after reaching a maximum value. The obvious enhancement in hardness for multilayers was observed, whose maximum value approaches 43.3 GPa when Λ = 8.4 nm, 37% larger than that obtained by the rule of mixture value. The friction coefficient values of NbN/NbCN multilayers ranging between 0.34 and 0.4 were much lower than that of NbN monolayer but higher than that of NbCN monolayer were.

Abstract: The authors construct a bridge between a microscale view and a nanoscale one in continuum mechanics. When the size of structure reduces to nanolevel, the ratio of surface to volume increases. Then, the surface stresses, which like to surface tension in fluid, influence on bulk stresses. In the present paper, the authors analyze a problem that anisotropic nanothin layers are deposited on a half substrate. Interface stresses and interface elasticity are taken into account for the boundary condition for each layer. Furthermore, misfit dislocation networks which generate from a mismatch of lattice parameters in crystals composing multilayers exist at each interface. A complicated interaction between misfit dislocation networks located at different interfaces will be demonstrated, and the results in the theory will be compared with those in a molecular dynamic method using a generalized embedded atomic potential.

Abstract: Thispaper presents the results of the studies of the combined influence of properties of carbide substrate and composite coatings on tool wear resistance in machining of chromium-based heat-resistant alloys. It was established that the efficiency of carbide tools with coatings is determined by a combination of the properties of the carbide substrate and the coating itself. For carbides with relatively low strength and crack resistance, the efficiency of coatings appeared to be unsatisfactory because of brittle fracture of the substrate and thus intensive failure of coating. High heat resistance of cobalt-rhenium alloy is not realized during deposition of coating because of blocking of the most important property of heat-resistant Co/Re binder, i.e. the ability to hold carbide grains under significant deterioration of carbide matrix even at a high temperature in the cutting zone.The maximum efficiency of the coating in machining of chromium-based heat-resistant alloy is provided withcarbide tools made with a balanced ratio of hardness, heat resistance and strength.