Kazuya Kusaka

Effects of nitrogen pressure and ion flux on the properties of direct current reactive magnetron sputtered Zr–N films

Zr–N films have been deposited by direct current reactive magnetron sputtering using a plasma emission monitoring (PEM) control system, where a signal proportional to the light emitted by the sputtered Zr in the plasma created by the electrical discharge was used to control the admission of the reactive nitrogen into the system. The Zr line set point for PEM control, φ, was used as a parameter; as the partial pressure of nitrogen rises the Zr line emission falls due to target poisoning. The influence of the nitrogen partial pressure on the Zr–N film structure, reflectivity, resistivity, and internal stress was investigated. The effect of ion flux during film deposition on the film properties was also investigated. The Zr–N films deposited at the Zr line set point φ=60%–70% revealed the minimum resistivity and goldlike reflectivity spectra. These films showed a ZrN single phase. The internal stress of the films showed a maximum at φ=60%–70%, which corresponds to the condition for depositing minimum resisti...

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.

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.

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.

Effect of nitrogen gas pressure on residual stress in A1N films deposited by the planar magnetron sputtering system

The crystal orientation and residual stress development in AIN films deposited on borosilicate (BLC) glass substrates were investigated by X-ray diffraction. Deposition was performed using two kinds of planar magnetron sputtering system: a conventional system (CPM system) and a special system with two facing targets (FTPM system). The nitrogen gas pressure (PN) was varied over a suitable range for each system. The diffraction patterns of the AIN films showed that the c-axis orientation was improved when the films were deposited using the CPM system at a nitrogen gas pressure lower than 1 Pa. For the CPM system, compressive residual stress was found in films deposited at PN≤2 Pa and tensile residual stress at P N > 2 Pa. For the FTPM system, tensile residual stress was found in films deposited at P N ≤0.8 Pa and Pa and tensile residual stress at PN> 2 Pa. For the FTPM system, tensile residual stress was found in films deposited at P N ≤ 0.8 Pa and compressive residual stress at P N > 0.8 Pa.

Film Degradation in AlN Preparation by Facing Target System

In AlN films prepared by the facing target system, a decrease in degree of c-axis orientation, film coloring and film cracking or peeling from the substrate were observed. This film degradation is thought to be related to insulative films in general. In order to clarify how these phenomena are induced, we prepared samples under various sputtering conditions; i.e., by changing target holders, placing a ground mesh in front of the substrate and using a positively biased electrode. It is confirmed that plasma exposure severely influences c-axis orientation of AlN films. To decrease this influence, it is important that electrons flow adequately into the anode.