Masateru Nose

Influence of sputtering conditions on the structure and properties of Ti-Si-N thin films prepared by r.f.-reactive sputtering

Abstract The influence of Si content and sputtering conditions on the microstructure and mechanical properties (hardness and Youngs modulus) of Ti–Si–N were investigated using XRD, XPS and nano-indentation. The composite targets consisting of a Ti plate and Si or Si 3 N 4 chips were sputtered in a mixture of argon and nitrogen. Ti–Si–N films were prepared in an r.f. sputtering apparatus of the facing target-type. During the deposition, the substrate was heated from room temperature up to ∼573 K and a bias of d.c. up to −100 V was applied. Without substrate heating and bias, the hardness of the films increased from 30 GPa for a binary system, reaching a maximum of 37 GPa for a ternary system with a small amount (3–8 at.%) of Si. It then decreased to lower values than those of binary systems when Si was more than 10 at.%. The tendency to grow columnar grains was strongest at approximately 5 at.% of Si. The hardness of Ti–Si–N films increased and reached to a maximum value of 42 GPa around at a bias of −10 V, but the crystallite size of the film remained larger than 23 nm. The increase of hardness with small amounts of Si in TiSiN films was probably associated with the lattice distortion. On the other hand, the increment of hardness of films containing 20 at.% of Si by the negative bias application could be attributed to the formation of nano-composite structure.

Microstructure and mechanical properties of Zr–Si–N films prepared by rf-reactive sputtering

ZrN and ZrSiN films were prepared in an rf sputtering apparatus that has a pair of targets facing each other (referred to as the facing target—type rf sputtering). Films were deposited on silicon wafers without bias application or substrate heating in order to examine only the effect of silicon addition to the transition metal nitride films. The contents of zirconium, nitrogen, and silicon of the films were determined with an electron probe microanalyzer. The transmission electron microscopy studies were carried out in addition to x-ray diffraction. For the high resolution transmission electron microscopy observation, the field emission type transmission electron microscope was used, which provides a point-to-point resolution of 0.1 nm. The samples were observed both parallel and perpendicular to the film surface, which were plane and cross sectional views, respectively. In order to investigate the relationship between the mechanical properties and microstructure of films, the hardness was measured by a n...

The effects of Si addition on the structure and mechanical properties of ZrN thin films deposited by an r.f. reactive sputtering method

Abstract The addition of Si to nitride films such as TiN or WN has been investigated to improve the mechanical properties of films. The aim of this study is to investigate the influence of Si addition on the structure and the mechanical properties of ZrN thin films. Thin films were synthesized by an r.f. reactive sputtering method in a facing target-type sputtering (FTS) machine on the substrates of silicon wafer and aluminum foils. The structure of thin films was studied by means of XRD and TEM. The hardness of the thin films was studied in detail by the nano-indentation system and the internal stress was evaluated by measuring the change of curvature induced in the sample. A study of their structure and mechanical properties has revealed as the following: (1) with increasing Si content, the hardness of the films increases initially, attaining a maximum hardness at approximately 3%, and then decreases to lower hardness than that of ZrN binary films; (2) the hardest film containing approximately 3% Si consists of large crystals in the range of 20–25 nm; (3) the increment in hardness of ZrSiN films by silicon addition cannot be explained by the crystal size; (4) the change of hardness with increasing Si content might be attributed to the change of internal stress.

Properties of Zr–Si–N coatings prepared by RF reactive sputtering

Abstract The aim of this paper is to examine the influence of Si addition on the structure and properties of Zr–N thin films. Zr–Si–N thin films were synthesized on stainless steel, silicon wafer and platinum substrates by RF reactive sputtering in a facing target-type sputtering machine (FTS). The structure of the thin films was studied by XRD and TEM, and the surface morphology was investigated by SEM. The hardness of the thin films was studied in detail using a nano-indentation system. A study of mechanical and oxidation resistance has provided the following conclusions: (i) with increasing Si concentration, the hardness of ZrSiN films increased initially, attaining a maximum hardness of 25 GPa at 5% Si, and then decreased gradually to 10 GPa at 15% Si; (ii) the oxidation resistance improved with increasing Si content, and reached the highest resistance at 10% Si; and (iii) ZrSiN film, by the addition of Si, exhibited a homogeneous fine structure.

Colorimetric properties of ZrN and TiN coatings prepared by DC reactive sputtering

Abstract The purpose of this work was to determine the dependence of the colorimetric properties of TiN and ZrN films on the sputtering conditions, especially on N 2 and Ar partial pressures. The color of films was evaluated quantitatively by means of the chromaticity coordinates x and y , and the luminous reflectance Y . The colorimetric study has provided the following conclusions: (1) The color of ZrN coatings is more sensitive than that of TiN coatings to nitrogen partial pressure. (2) The bright gold color of ZrN coatings can be obtained by sputtering, even at the relatively higher pressure of 0.3 Pa (at high argon flow rate). On the other hand, a bright gold color for TiN coatings is only observed at the lower pressure of 0.15 Pa (low argon flow rate). (3) ZrN coatings can be made to exhibit the golden color, which is as bright as 24-carat gold, but slighter whitish, and TiN can be made to show the golden color, which has the same hue as the gold, but of slightly lower brightness. (4) Oxygen content in TiN coatings increases with increasing argon partial pressure. This tendency corresponds to the dependence of luminous reflectance and resistivity of this material on the argon partial pressure.

Electrical and colorimetric properties of TiN thin films prepared by DC reactive sputtering in a facing targets sputtering (FTS) system

Abstract The aims of the present work are twofold: first, to confirm the condition for obtaining gold–yellow TiN films without bias application; second, to examine the quantitative relationship between the colorimetric properties and electrical resistivity of these films. For the first aim, TiN films were prepared by DC reactive sputtering under a no-bias condition in the facing targets sputtering (FTS) apparatus, in which discharge is maintained even at a low gas pressure of less than 0.3 Pa. For the second aim, the color of the films was evaluated by means of the chromaticity coordinates, x and y , and the luminance factor Y , which is an index of the brightness based on a CIE standard colorimetric system. Gold–yellow TiN films having low resistivity were obtained, and a study of their electrical and colorimetric properties has provided the following conclusions. (i) The colorimetry of the films is affected by both the mixing ratio and total gas pressure. In particular, the brightness (the luminance factor) Y varied greatly with a change in total gas pressure. (ii) Even without bias application, a gold-colored TiN film with higher brightness Y has been obtained by deposition at an appropriate mixing ratio of N 2 /Ar and also under lower total gas pressure ( ρ =0.31 μΩ m and Y =49 for the films deposited at 0.15 Pa). (iii) As the total gas pressure was increased, the column size, the surface roughness and oxygen content showed a clear increase. Thus, the films deposited under an atmosphere higher than 0.15 Pa had higher resistivity and lower brightness. (iv) Based on our results, the quantitative relationship between the resistivity and brightness of the TiN films is shown by the relation of ρ =775 Y −2 .

Structure and properties of Cr–B, Cr–B–N and multilayer Cr–B/Cr–B–N thin films prepared by r.f.-sputtering

Abstract Cr–B, Cr–B–N and Cr–B/Cr–B–N multilayer films were synthesized by r.f. plasma-assisted magnetron sputtering using a CrB target (99.9% in purity) on silicon wafer substrates. The multilayer coatings were prepared by sequential sputtering using a nitrogen gas flow controller and a shutter by the sputtering of the CrB target. The films were deposited with an r.f. power of 120 W (target) and 100 W (coil) without substrate bias application, and the film thickness was controlled to ∼1 μm by adjusting the sputtering time. The micro-structure of thin films was studied by XRD and TEM and the chemical bonding state of films was investigated by XPS. The hardness and Youngs modulus of the films were studied in detail by the nano-indentation system. A ball-on-disk tribometer was used to measure the friction and wear behavior. A study of their microstructure and mechanical properties has provided the following results: XRD, TEM and XPS measurements revealed that the Cr–B films consist of CrB phase mainly and Cr–B–N films contain CrB and h-BN phase with an amount of unknown phases. The hardness for the films of Cr–B and Cr–B–N was 17 and 13 GPa, respectively. On the other hand, Cr–B/Cr–B–N multilayer films exhibited higher hardness reaching to 20 GPa regardless of the sublayer thickness. Cr–B and Cr–B–N films showed the Youngs modulus of 204 and 216 GPa, respectively. The Youngs modulus of Cr–B/Cr–B–N multilayer films increased to approximately 240 GPa regardless of the sublayer thickness as well. Furthermore, the friction coefficient of Cr–B/Cr–B-N multilayer exhibited an intermediate value of ∼0.45 between those of Cr–B (0.9) and Cr–B–N (0.2).

Annealing effects on the structure and mechanical properties of r.f.-sputtered Cr–B hard thin films

Cr–B thin films were synthesized by an r.f. plasma-assisted magnetron sputtering method using pure CrB2 target on quartz glass, glass ceramic, NaCl single crystal and silicon wafer substrates. After the sputtering process, the as-deposited Cr–B thin films were annealed at 773, 973 and 1173 K for 5 h. The influence of annealing temperature on the structure and properties of Cr–B thin films was investigated. Although the films were deposited at low temperature (TS/TM<0.1) in this study, X-ray diffraction and transmission electron microscopy observation results indicate that fine crystalline grains are still formed in these films. With increasing annealing temperature, the grain size increased gradually from 10 to 30 nm. The compressive stress in the Cr–B films is rather small due to the long target–substrate distance of this apparatus which reduces the atomic peening effect. The hardness decreased scarcely with increasing annealing temperature from about 21 GPa for as deposited to about 19 GPa for 1173 K owing to the grain growth and relaxation of residual stress. The present study shows that Cr–B thin films can be used below 1200 K with stable structure and high hardness.

Influence of sputtering conditions on microstructure and mechanical properties of Zr–Si–N films prepared by radio-frequency-reactive sputtering

ZrN and ZrSiN films were prepared in an rf-sputtering apparatus which has a pair of targets facing each other (referred to as the facing target-type rf sputtering). In order to investigate the influence of substrate temperature on the structure and mechanical properties of Zr–Si–N films, the substrate temperature during the deposition was changed from 373 K to 673 K. Only one phase with a cubic B1 NaCl structure, typical for ZrN, can be clearly identified in all Zr–Si–N films in this study. Increasing substrate temperature can improve crystalline quality in all Zr–Si–N films in this study. Grain sizes of all Zr–Si–N thin films, despite the Si content, increase linearly with increasing substrate temperature. However, the grain growth speed with increasing substrate temperature in a pure ZrN thin film is much faster than that in Zr–Si–N thin films, because Si atom occupation of interstitial sites tends to lock diffusion paths and thus stabilize the structure. The hardness of Zr–Si–N films with low Si conten...

Deposition of novel nanocomposite films by a newly developed differential pumping co-sputtering system

A differential pumping co-sputtering system was developed to facilitate a controlled, but flexible fabrication of multifunctional nanocomposite films with compositions not limited by thermodynamic restrictions. This system features a multichamber design with a differential pumping system. Dividing atmospheres with this set up greatly reduced the cross-contamination between chambers, and each material could be co-deposited by rapid rotation of the substrate. The clearance between the substrate holder and the chamber was set at 1–2 mm, and the conductance of the clearance was examined roughly using conductance equations for typical types of orifices. It was found that the potential difference (PD) value of the clearance between the two chambers was less than 0.01; the gas flow between the two chambers through the clearance thus appears to be a practical molecular flow. The PD value, where P is a pressure (Pa) and D is a diameter of an orifice or a pipe (m), is a gas flow indicator or parameter obtained from an equation of Knudsen number. The changes in the oxygen partial pressure and glow discharge plasma in the left chamber were investigated using a process gas monitor (PGM) and optical emission spectroscope (OES) by introducing different gases to each chamber. The PGM results revealed that the cross-contamination of oxygen from the other chamber was suppressed to 10 ± 3% of the original. In addition, the OES measurement for glow discharge plasma did not detect substantial oxygen contamination from the other chamber. Using the newly developed system, an AlN/SiOx nanocomposite film consisting of B4-type AlN and amorphous SiOx was obtained successfully.A differential pumping co-sputtering system was developed to facilitate a controlled, but flexible fabrication of multifunctional nanocomposite films with compositions not limited by thermodynamic restrictions. This system features a multichamber design with a differential pumping system. Dividing atmospheres with this set up greatly reduced the cross-contamination between chambers, and each material could be co-deposited by rapid rotation of the substrate. The clearance between the substrate holder and the chamber was set at 1–2 mm, and the conductance of the clearance was examined roughly using conductance equations for typical types of orifices. It was found that the potential difference (PD) value of the clearance between the two chambers was less than 0.01; the gas flow between the two chambers through the clearance thus appears to be a practical molecular flow. The PD value, where P is a pressure (Pa) and D is a diameter of an orifice or a pipe (m), is a gas flow indicator or parameter obtained from...