Takao Hanabusa

Residual stress and in-situ thermal stress measurement of aluminum film deposited on silicon wafer

Abstract Residual stresses in aluminum film deposited on a silicon wafer were measured after annealing and quenching. In all cases, residual stresses were tensile, but slow cooling produced larger stresses than quenching. Residual stresses of slow-cooled samples became relaxed after annealing above 300 °C. Film passivation by carbon deposition retarded the relaxation of residual stress. In-situ X-ray stress measurement revealed that compressive stresses developed in a heating stage and tensile stresses in a cooling stage. From a scanning electron microscopy observation, it becomes clear that the former contributes to nucleation of hillocks and the latter to void formation and growth.

Residual stress and its thermal relaxation in TiN films

Abstract The structure and residual stresses of TiN coated films were investigated by X-ray diffraction. TiN films were deposited onto substrates of spring steel by a multi-are method at different deposition temperatures. The TiN films, approximately 4 μm in thickness, exhibited high {111} orientation. The residual stresses in the TiN films were evaluated by the two-exposure method to obtain the lattice strains for 222 diffraction at ψ=0° and 70.5° with Cu Kα radiation. The results revealed very high compressive residual stresses of about −5.8 to −3.5 GPa which are one order larger than the thermal residual stress expected from the thermal strain mismatch between the film and the substrate. These residual stresses in the TiN films decreased on increasing the annealing temperature, and decreased finally to the level of the thermal residual stress after annealing at temperatures above 1073 K.

X-ray residual stress measurement of laminated coating layers produced by plasma spraying

Abstract The present paper describes residual stress in laminated layers deposited by thermal spraying on a low carbon steel substrate. Laminated layers were made of Al 2 O 3 −NiCr or Al 2 O 3 −NiAl with various combinations of mixing ratios. X-ray diffraction was used to measure residual stress in the outermost surface layer. The results of finite-element method (FEM) thermal stress analysis were compared with the experimental results of X-ray measurements. From the X-ray stress measurements, tensile residual stress (100–300 MPa) was measured in the as-coated surface layers of all specimens. The effect of annealing on residual stress variation was also examined. In the case of the Al 2 O 3 (100%) layer of the Al 2 O 3 −NiCr system, residual stress of surface layers was not greatly affected by the method of lamination and did not change significantly upon annealing. In contrast, in the layer with mixed Al 2 O 3 and NiAl, residual stress in the as-coated layer was influenced by the mixing ratio of Al 2 O 3 and NiAl. Furthermore, residual stresses were gradually reduced in both the Al 2 O 3 and Ni phase following annealing. FEM calculation revealed that large compressive residual stress (about —2 GPa) was produced in the 100% Al 2 O 3 layer after a full annealing treatment. The value of residual stress depends on the difference between the thermal expansion coefficients of the laminated layers and the substrate. This result was exactly opposite to the experimental results for the fully annealed Al 2 O 3 −NiCr system. However, residual stresses in the mixed layer (Al 2 O 3 −NiAl) depended on the mixing ration of Al 2 O 3 and NiAl. This agrees qualitatively with the experimental results.

Abnormal residual stress state in ZnO films synthesized by planar magnetron sputtering system with two facing targets

Abstract The structure and residual stresses of ZnO films synthesized by a planar magnetron sputtering system with two facing targets were investigated by X-ray diffraction. ZnO films were deposited onto a sheet of Corning 7059 glass. The X-ray diffraction pattern shows that the film has high 00·1 orientation. Residual strains were measured on various diffraction lines that appear at special angles ψ from the surface normal. The strains taken from positive and negative ψ differed from each other. This behavior is deduced from the existence of a shear stress component in a cross-section of the film. The magnitude of the shear stress increased with increasing current density of the Zn target as well as with decreasing argon gas pressure.

Effect of external magnetic field on c-axis orientation and residual stress in AlN films

Abstract Crystal orientation and residual stress development in AlN films on borosilicate glass (the thermal expansion coefficient of which is nearly equal to that of AlN) substrate were investigated by atomic force microscopy (AFM) observation and X-ray diffraction method. The AlN films were prepared by a planar magnetron sputtering system with two opposite targets under the condition of constant nitrogen gas pressure, constant substrate temperature, various deposition time and various external magnetic field (EM) between 63 and 128 gauss. We obtain the following results: (1) the size of crystal grains was large and the value of FWHM of 00·2 diffraction line was small at large EM; (2) the c -axis orientation was good for all films; (3) the large tensile residual stresses were obtained at large EM and decreased with decreasing the EM because of ion peening.

Residual stress in TiN film deposited by arc ion plating

Abstract TiN films were deposited on aluminum and stainless steel substrates by arc ion plating (AIP). Bias voltages, nitrogen gas pressures and arc currents were changed to examine their role on the hardness and residual stress of a TiN film. Vickers microhardness tests revealed high hardness value (HV = 2250–2500) which depends on both nitrogen gas pressures and arc currents. From the X-ray diffraction pattern, it was found that the crystal orientation of the TiN film markedly varied with the bias voltage. Residual stresses in the TiN film were measured by the two-exposure X-ray stress analysis as a function of the nitrogen gas pressure, arc current. Very high compressive residual stresses, −5 GPa in the films on aluminum substrates and −7 GPa in the film on a stainless steel substrate, were observed.

Simulation of the thermo-mechanical behavior and residual stresses in the spray coating process

Abstract In order to be able to forecast the thermo-mechanical behavior and the residual stress in the spray coating process, a continuum mecromechanical model for describing the interaction involving temperature, the solidifying mode and, the stress/strain curve is developed in this paper. A set of coupled equations of the heat conduction, stress/strain and solidification is given by the metallo-thermo-mechanical theory. For this simulation, a numerical modeling based on the finite element method for calculating the heat conduction associated with solidification and the stresses at the interface between multi-layer materials is proposed. Here, the temperature field, the solidified state and the residual stresses of the spray coating process, including interfacial combinations between substrate and sprayed layer, are presented, and the validity of the calculated results is discussed in comparison with experimental X-ray results.

TiN films prepared by unbalanced planar magnetron sputtering under control of photoemission of Ti

Abstract TiN films have been prepared by unbalanced planar magnetron sputtering, where the flux of sputtered Ti atoms was maintained constant by adjusting N2 gas flow during sputtering. At a set point of 75% of the Ti signal in pure Ar gas, the film resistivity has a minimum, the film stress becomes a minimum and the appearance is most gold-like. With an increase in ion bombardment, the internal stress increases, whereas the film resistivity decreases. These results confirm that stoichiometric TiN films are prepared at the set point of 75%, where the target surface is not fully covered by TiN. The energetic ions appear to improve the properties of the TiN films.

Effect of substrate temperature on crystal orientation and residual stress in radio frequency sputtered gallium–nitride films

The crystal orientation and residual stress in gallium nitride (GaN) films deposited on a single-crystal (0001) sapphire substrate using a sputtering system are examined through x-ray diffraction measurements as part of a study of low-temperature sputtering techniques for GaN. The rf sputtering system has an isolated deposition chamber to prevent contamination with impurities, and is expected to produce high-purity nitride films. GaN films are deposited at various substrate temperatures and constant gas pressure and input power. This system is found to produce GaN films with good crystal orientation, with the c axes of GaN crystals oriented normal to the substrate surface. The crystal size of films deposited at high temperature is larger than that deposited at low Ts. All films except that deposited at 973 K exhibit compressive residual stress, and this residual stress is found to decrease with increasing temperature. Finally, the film deposited at 973 K was tinged with white, and the surface contained nu...

Energetic oxygen ions in ZrO2 deposition by reactive sputtering of Zr

Abstract The generation of intense flux of energetic oxygen ions in the sputtering of Zr target in Ar+O 2 atmosphere is investigated. The energetic negative oxygen ions were detected using a constructed probe. The photoemission intensity of sputtered Zr atoms was observed in order to monitor the surface oxidization of the Zr target. The results indicate that the surface of the Zr target undergoes rapid oxidization during sputtering. The generation of the intense flux of energetic negative oxygen ions is considered to occur as a result of sputtering the heavily oxidized Zr target.