Naoto Kuratani

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.

The synthesis and properties of BN films prepared by ion irradiation and vapor deposition

Abstract Boron nitride films were deposited on tungsten carbide substrates by evaporation of boron and simultaneous nitrogen ion irradiation with energies in the range of 0.2 to 20.0 keV. The effect of preparation conditions on the mechanical properties such as hardness and adhesion was studied, and the deposition process for obtaining a hard film with good adhesion was investigated. For stoichiometric films, decreasing the ion energy increased the hardness, but decreased the film adhesion. On the other hand, boron-rich films showed a better adhesion, but a decrease in hardness. From these results, multilayer films were prepared using high and low energy ions; stoichiometric films prepared by low energy ions were deposited on boron-rich films prepared by high energy ions. The multilayer films combined the advantages of both preparation conditions, high hardness and enhanced adhesion.

Fundamental study of ion-irradiation effects on the columnar growth of chromium films prepared by ion-beam and vapor deposition

The effects of ion irradiation during deposition on columnar growth of Cr thin films prepared by ion-beam-assisted deposition were studied. Cr films were prepared by evaporation of Cr metal and simultaneous irradiation of Ar ions onto Si 〈100〉 wafers. The energies of Ar ions were varied over the range of 0.5–20.0 keV, and the transport ratios of irradiating Ar ions to depositing Cr atoms, TR(Ar/Cr), to the substrates were also varied between 0.01 and 0.20. Vaporized Cr atoms were deposited onto substrates at an angle of 45° from the substrate normal and Ar ions were irradiated perpendicular to the substrate surface. Si substrates were not rotated and were kept at low temperature during deposition by a water-cooling system. The experimental results showed that every Cr film had a columnar structure regardless of ion-irradiation conditions. The column size became larger with increasing ion energy and TR(Ar/Cr). The growth direction of the column tilted considerably with increasing ion energy and TR(Ar/Cr) i...

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.

Boron nitride hard coatings by ion beam and vapor deposition

Abstract Boron nitride (BN) thin films were synthesized by ion beam and vapor deposition (IVD) process. Boron was deposited on substrates and nitrogen ions were simultaneously irradiated to the depositing film. The energies of nitrogen ions were 2.0 keV. The multilayercd films were deposited to improve the film adhesion: B-rich BN films were formed on substrates and stoichiometric films were deposited on the B-rich BN films. In order to evaluate the behaviour of the multilayered BN films at high temperatures, the heat treatments (from 500 to 800°C) were performed in a nitrogen and air atmosphere. Crystalline structures of the films were determined by IR analyses. The results indicated that the main phases of the multilayered BN films were cubic, and the crystalline structures were unchanged up to 800°C in a nitrogen atmosphere. In the case of the heat treatment in air, the crystalline structure of the film was changed at 750°C. Compression moulding tests by forming bolosilicate glass lenses were performed at 630°C using the multilayered BN coated moulding die. The BN films prepared by IVD process had a mirror finish, and the surface roughness of the moulding die was not changed after the glass moulding tests. XPS analyses showed that the multilayered BN film on the moulding die had excellent corrosion resistance for applications of the glass-forming.

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.

Influences of ion energy on morphology and preferred orientation of chromium thin films prepared by ion beam and vapor deposition

The influences of ion irradiation on morphologies and preferred orientations of Cr thin films prepared by ion-beam and vapor deposition were studied. Cr films were prepared onto Si 〈100〉 wafers by evaporation of Cr and simultaneous irradiation with Ar ions. The energies of Ar ions were changed in the range of 0.5–20.0 keV, and transport ratios of irradiated Ar ions to vaporized Cr atoms, Ar/Cr, to the substrates were kept at 0.033. Vaporized Cr atoms were deposited onto substrates at an angle of 45° and Ar ions were irradiated normal to the substrates. Si substrates were kept at low temperature during deposition. The experimental results show that the morphologies and the preferred orientations were varied due to the change of ion irradiating energy though other conditions were constant. Every Cr film takes a clear columnar structure. The column widths of Cr films are augmented with increase of ion energy. The columnar growth direction turns toward the deposition direction with increase of ion energy up t...

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.