Osamu Imai

Internal stress in thin films prepared by ion beam and vapor deposition

Abstract The effect of ion beam irradiation on the internal stress in thin films prepared by ion beam and vapor deposition (IVD) was studied. The thin films were prepared by the evaporation of nickel or silicon metals and simultaneous irradiation on Si(100) substrates by argon ion beams. The energies of the argon ions were changed in the range 0.5–10.0 keV, while the transport ratio of vapor atoms to ions was changed from 5 to 15. The internal stresses in the thin films were measured by the displacements of the substrates after deposition, and the results show that the internal stress changed from compressive to tensile with increasing ion beam energy. In addition, the control of the internal stresses in multilayer films prepared by IVD was investigated. It was found that it is possible to control the internal stress in a multilayer film by a suitable combination of the layers.

Effect of sputtering-cleaning on adhesion of the metallic films to polymer substrates

Abstract The effect of sputtering-cleaning on adhesion and chemical bonding at the metal/polymer interface was studied. Titanium (Ti) films were deposited on polymer substrates, polyethylene and polytetrafluoroethylene (PTFE) after sputtering-cleaning treatment. The sputteringcleaning treatment consisted of argon ion irradiation at 0.3 keV. Adhesion was measured by a pull test, and the chemical bonding at the interface was investigated by X-ray photoelectron spectroscopy. Adhesion of both polymer substrates was improved by sputtering-cleaning. In the case of PE, the ratio of C-Ti bonding at the interface increased after sputtering-cleaning and resulted in adhesion improvement. C-Ti and F-Ti bonding appeared at the interface between the Ti film and the PTFE substrate, but improvement in adhesion of Ti/PTFE was attributed to the change of the interfacial morphology on the basis of the scanning electron spectroscopy observation and adhesion of Au to PTFE.

Improvement of the adhesion to polyimide substrates of copper films prepared by an ion beam and vapor deposition (IVD) method

Abstract Copper films were prepared by evaporation of copper metal and simultaneous bombardment by nitrogen ions with ion energy in the range 0.2 keV to 2.0 keV. The adhesion of copper films was improved by increasing the ion energy of the nitrogen ions. The copper film prepared with 2.0 keV nitrogen ions had the strongest adhesion. The structure of the interlayer between the copper film and the polyimide substrate was evaluated by transmission electron microscopy. The copper atoms were diffused into the polyimide substrate by nitrogen ion bombardment. The chemical states of the polyimide film surface and the chemical binding states at the interlayer were analyzed by X-ray photoelectron spectrometry. Nitrogen ion bombardment caused carbonization of the polyimide surface, and the irradiated nitrogen ions combined with the carbon atoms of the polyimide film. At the interlayer, X-ray photoclcctron spectrometry showed that copper compounds were formed by nitrogen ion bombardment. It was considered that the increase in adhesion due to nitrogen ion bombardment could be attributed to a combination of the anchor effect caused by the diffusion of copper atoms into the substrate and the formation of copper compounds at the interlayer.

Influences of intermediate Si-Ni thin film conditions on adhesion of Ni-TiN gradient thick films

The influences of the intermediate thin film properties, that is internal stress and preferred orientation, on the adhesion of thick film were studied. The intermediate layers were designed Si and Ni multilayer structures, which were formed by the ion beam and vapor deposition method. Si films were prepared by evaporation of Si and simultaneous irradiation with Ar ions on to WC-Co substrates after surface cleaning by Ar ion beam irradiation. After the preparation of Si films, Ni films were also prepared by evaporation of Ni and Ar ion irradiation simultaneously. The internal stresses and preferred orientations of both films were controlled by changing the ion beam energy. Ni-TiN gradient thick films were formed on to these Si-Ni multilayer films by the cathodic arc ion plating method. It was found that the improvements of the internal stress and the preferred orientation conformities at the interface between the intermediate films and the thick films were important factors for high adhesion of thick film. The Ni-TiN gradient thick film reached a thickness of 600 μm with an adhesion high enough for practical use.

Roles of ion irradiation for crystalline growth and internal stresses in nickel films onto silicon substrates prepared by the ion beam and vapor deposition method

The roles of ion irradiation for crystalline growth and internal stresses in Ni films prepared by the ion beam and vapor deposition method were studied. Ni films were prepared on Si〈100〉 wafers by evaporation of Ni metal and simultaneous irradiation with inert gas ions, Ne, Ar, Kr, and Xe. The energies of inert gas ions were changed in the range of 0.5–10.0 keV. Transport ratios of vaporized Ni atoms to inert gas ions to substrates were kept at 15. Ion beam current densities and ion irradiation directions were fixed at 40 μA/cm2 and perpendicular to the substrate surface, respectively. From the x-ray analyses, crystallinities and preferred orientation were changed by ion irradiation conditions. On the other hand, internal stresses were also changed from compressive to tensile depending on ion energies and ion species. It is understood that the variations of crystalline growth and internal stresses in Ni films were caused by the difference of nuclear and electronic energy transfer abilities of irradiating ions.The roles of ion irradiation for crystalline growth and internal stresses in Ni films prepared by the ion beam and vapor deposition method were studied. Ni films were prepared on Si〈100〉 wafers by evaporation of Ni metal and simultaneous irradiation with inert gas ions, Ne, Ar, Kr, and Xe. The energies of inert gas ions were changed in the range of 0.5–10.0 keV. Transport ratios of vaporized Ni atoms to inert gas ions to substrates were kept at 15. Ion beam current densities and ion irradiation directions were fixed at 40 μA/cm2 and perpendicular to the substrate surface, respectively. From the x-ray analyses, crystallinities and preferred orientation were changed by ion irradiation conditions. On the other hand, internal stresses were also changed from compressive to tensile depending on ion energies and ion species. It is understood that the variations of crystalline growth and internal stresses in Ni films were caused by the difference of nuclear and electronic energy transfer abilities of irradiating ...

Internal stresses in nickel films prepared by ion beam and vapor deposition

Abstract The effect of the ion beam irradiation on the internal stresses in nickel films prepared by ion beam and vapor deposition (IVD) method was studied. The nickel films were prepared on the silicon (100) wafers by evaporation of nickel and simultaneous irradiation with inert gas ions, such as neon, argon, krypton and xenon. The energy of inert gas ion bombardment was changed in the range of 0.5–10.0 keV. The transport ratios of vapor atoms to inert gas ions, atoms/ions, to the substrate were kept at 15. The internal stresses in nickel films were determined by measuring the change in the substrate curvature after deposition. The results show that the internal stresses in the films depend on the ion beam energy and the ion species. In addition, the correlation between the crystal structures and the internal stresses was also investigated. The internal stresses depend on the crystallinity and the preferred orientation.

Study on the effect of the interlayer on the adhesion of 400 μm thick film

Abstract We have studied on the effect of the interlayers on the adhesion of 400 μm thick NiTiN gradient films. In order to improve the adhesion of the NiTiN films, the interlayer films are formed at the interfaces between the thick films and tungsten carbide substrates (WC-Co). The interlayers have the SiNi multilayer structures and are prepared by ion beam and vapor deposition (IVD) method. The Si interlayers are prepared at various internal stresses on tungsten carbide substrates and the Ni interlayers also are prepared at various internal stresses on the Si interlayers. The 400 μm thick films are formed by cathodic are ion-plating method on the SiNi interlayers. As a result, it seems that it is possible to improve the adhesion of the thick films by decreasing internal stress mismatch among the lower layers of the thick films, upper layers of interlayers and lower layers of interlayers.

INTERFACE STRUCTURE BETWEEN POLYIMIDE FILM SUBSTRATE AND COPPER FILM PREPARED BY ION BEAM AND VAPOR DEPOSITION (IVD) METHOD

Abstract The effects of improvement of copper film adhesion prepared on polyimide film substrate were investigated. The copper thin films on polyimide films were prepared by evaporation of copper metal and simultaneous irradiation of argon gas ions with energies in the range of 0.5 to 10.0 keV. The structures at the interface between the copper films and polyimide substrates were analyzed by transmission electron microscopy (TEM). TEM analysis showed that the ion bombardment formed the mixed layer which consisted of the polyimide elements and copper atoms at the interface. The thicknesses of the intermixed layers were evaluated by using energy dispersive X-ray spectroscopy (EDXS) analysis. The thicknesses of the mixed layers were increased with an increase of ion dose and ion energy. The adhesion of copper films was evaluated by means of a peel test. The test showed that the film adhesion was dependent on the conditions of the ion bombardment, the adhesion was improved by the formation of the intermixed layer, but high energy ions, which increased the thicknesses of the intermixed layers, decreased the film adhesion. It is revealed that the high energy ions caused the carbonization at the polyimide surfaces. The improvement of the film adhesion depends on the formation of intermixed layer but also on the carbonization at the polyimide surface.

Study on the internal stress in nickel films deposited onto silicon substrates by ion beam and vapor deposition (IVD)

Abstract The effect of ion irradiation during deposition, in particular the effect of the formation of mixing layers at the interface between the film and the substrate by ion mixing, on the internal stress in nickel films deposited onto silicon substrates was studied. The nickel films were prepared on silicon (100) wafers by evaporation of nickel and simultaneous irradiation with inert gas ions (ion beam and vapor deposition method). The energy of inert gas ion bombardment was varied in the range 0.5–10.0 keV. The transport ratios of vapor atoms to inert gas ions, atoms/ions, to the substrates were constant at 15. The silicon substrates were kept at a low temperature by a water cooling system. The internal stress in the nickel films was determined by measuring the change in curvature of the substrates. From X-ray analysis and annealing experiments, it is considered that one of the main causes of tensile stress in nickel films prepared on silicon substrates by IVD is the formation by ion mixing of an Ni 2 Si layer at the interface.

Study on the crystallization of nickel films prepared by the ion beam and vapour deposition method

Abstract The effect of ion irradiation on the crystallization of the nickel films prepared by the ion beam and vapour deposition (IVD) method was studied. The nickel films were prepared on the silicon (100) wafers by evaporation of nickel and simultaneous irradiation with inert gas ions, such as neon, argon, krypton and xenon. The energy of inert gas ion bombardment was changed in the range 0.5–10.0 keV. The crystallization states of the films were analyzed by X-ray diffraction. X-ray diffraction patterns indicated that the (111), (200) and (220) crystallinity depended strongly on both ion beam energy and ion species. We studied the effect of ion irradiation on the crystallization of nickel films in terms of stopping cross-section of the ions. It seems that in the case of ion irradiation which is dominated by the nuclear stopping cross-section, the crystallization of the 〈111〉 orientation is promoted strongly; and as the effect of the electronic stopping cross-section increases, the orientation of the crystallization is changed in the order of 〈100〉 and 〈110〉.