井上 尚三

(Ti, Al)N films have drawn much attention as alternatives for TiN coatings, which are oxidized easily in air above 500 degrees C. We have investigated the effect of Al content on the oxidation resistance of (Ti1-xAlx)N films prepared by r.f. reactive sputtering. (Ti1-xAlx)N films (0 less than or equal to x less than or equal to 0.55) were deposited onto fused quartz substrates by r.f. reactive sputtering. Composite targets with five kinds of Al-to-Ti area ratio were used. The sputtering gas was Ar (purity, 5 N) and N-2 (5 N). The flow rate of Ar and N-2 gas was kept constant at 0.8 and 1.2 sccm, respectively, resulting in a sputtering pressure of 0.4 Pa. The r.f. power was 300 W for all experiments. Substrates were not intentionally heated during deposition. The deposited films (thickness, 300 nm) were annealed in air at 600 similar to 900 degrees C and then subjected to X-ray diffractometer and Auger depth profiling. The as-deposited (Ti1-xAlx)N films had the same crystal structure as TiN (NaCl type). Al atoms seemed to substitute for Ti in lattice sites. The preferential orientation of the films changed with the Al content of the film, x. Oxide layers of the films grew during annealing and became thicker as the annealing temperature increased. The thickness of the oxide layer grown on the film surface decreased with increasing Al content in the film. For high Al content films an Al-rich oxide layer was grown on the surface, which seemed to prevent further oxidation. All of the films, however, were oxidized by 900 degrees C annealing, even if the Al content was increased up to 0.55. (C) 1997 Elsevier Science S.A.

TiN films have many useful properties such as extreme high microhardness, resistance to wear, resistance to friction, and so on. However, relatively poor resistivity against oxidation is shown at high temperature. The purpose of this work is to investigate the oxidation behavior of the AlN/TiN double layer films as an alternative to TiN films. TiN single layer films (thickness; 300 nm) and AlN (100 nm)/TiN(200 nm) double layer films were deposited onto (001) Si wafers using rf reactive sputtering apparatus with two planar magnetron type cathodes. The targets were pure Ti ( >99.9%) and pure Al (> 99.999%) disks (70 mm in diameter). An Ar+N-2 mixed gas (Ar : N-2=1 : 1, total pressure 0.4 Pa) was used as the sputtering gas. The substrate temperature and rf power were kept constant at R.T. and 300 W, respectively. The deposited films were annealed in the air environment at 400 similar to 700 degrees C for 60 min and then subjected to Auger depth profiling. The as-deposited AlN/TiN interface appeared to be free from contamination and interdiffusion. There was no evidence of the existence of compound formation at the interface. X-ray diffraction analysis revealed that the AIN crystalline layer had an 00. 2 preferred orientation on the weakly 001 oriented TiN layer. The oxide layer of similar to 200 nm was formed on the TiN single layer films by annealing at 600 degrees C for 60 min. On the contrary, the AlN/TiN double layer films showed excellent oxidation resistance even when annealing at 700 degrees C.

TiN films have been prepared by unbalanced planar magnetron sputtering, where the flux of sputtered Ti atoms was maintained constant by adjusting N-2 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.

(Ti, Al) alloy nitride films have drawn much attention because of their excellent oxidation resistance. The purpose of this paper is to investigate the structure, morphology and composition of the (TiXAl1-XNY films prepared by r.f. reactive sputtering using a composite target where the area ratio of Ti to Al is unity. Nitrogen flow to total nitrogen and argon flow ratio (F-N2/F-total) is used as a parameter. The partial pressures of these gases that resulted were monitored by their optical emission in the glow discharge. The crystallographic structure of deposited films were divided into three groups by the F-N2/F-total that was used in their preparation. The first group (F-N2/F-total=0) is a Ti and Al metal mixed structure. The second group (0.1 less than or equal to F-N2/F-total < 0.4) has an amorphous structure. The last group (F-N2/F-total greater than or equal to 0.4) has the wurtzite structure. Under all conditions, the composition of the films was richer in Al than the target area ratio of Ti to Al, as would be expected from their sputtering yields. This ratio changes with admission of nitrogen because of selective poisoning (the formation of nitrides on the sputtering target). The plot of composition ratio C-Ti/C-Al vs. F-N2/F-total showed the local minimum at about F-N2/F-total = 0.3. The ratio of Ti to Al emission intensity, I-Ti/I-Al, from optical measurements shows excellent agreement with C-Ti/C-Al. It is concluded that the optical emission signal is very useful for the composition control during deposition, both of the materials being sputtered and of the residual atmosphere.

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, phi, 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 phi=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 phi=60%-70%, which corresponds to the condition for depositing minimum resistivity films. The external magnetic field scarcely affected the optical and the electrical properties of the deposited Zr-N films. The internal stress of the films deposited at the lower phi (higher nitrogen partial pressure) was only dependent on the ion flux. (C) 1995 American Vacuum Society.

The r.f. reactive sputtering of a Ti target in a mixed gas of Ar and N-2 was used to fabricate compositionally gradient films consisting of Ti and TiN phases. In this paper, two methods are described to form the compositionally gradient Ti-TiN films. The first uses the N-2 flow-to-total flow ratio (F-N2/F-total) control method, and the other is the r.f. power control method. The compositionally gradient Ti-TiN films were deposited onto microscope glass slides. The substrate was at room temperature. The crystallographic structure, the composition and the morphology of the deposited films were characterized by X-ray diffractometry, Auger electron spectroscopy and scanning electron microscopy, respectively. Both the F-N2/F-total and r.f. power control method can be used to grow compositionally gradient films. It was demonstrated that the deposited film has a structure with a non-oriented TiN layer on a c-axis perpendicular Ti layer. The morphology of the films is independent of the deposition method. It is also shown that optical emission spectroscopy and mass spectroscopy are useful tools to monitor the growth of these films.

The rf reactive sputtering of Al target in Ar+N2 mixed gas was applied to fabricate the compositionally gradient films consisting of Al and AlN phases. In this paper, two methods are presented to form the compositionally gradient Al-AlN films. The first is the N2 partial pressure-to-total pressure ratio (P(N2)/P(total)) control method, and the other is the rf power control method. The compositionally gradient Al-AIN films were deposited onto slide glasses, and the substrate temperature were room temperature and 200-degrees-C. The crystallographic structure, the composition and the morphology of deposited films were characterized by X-ray diffractometry, Auger electron spectroscopy and scanning electron microscopy, respectively. Both the P(N2)/P(total) and rf power control methods can be used to grow the compositionally gradient films. It is demonstrated that the deposited film has the structure with a c-axis perpendicular AlN layer on a non-oriented Al layer. The morphology of the films is greatly dependent on the substrate temperature, independently of the deposition method. It is also shown that the optical emission spectroscopy and the mass spectroscopy are useful tools to monitor the growth of these films.

TiN films have wide-ranging applications from erosion resistant coatings for cutting tools to diffusion barriers in LSI devices. The purpose of this work is to investigate the growth process of reactive sputtered TiN films. TiN(x) films were deposited onto air cleaved (001)NaCl single crystals by rf sputtering of 99.9% Ti disk (70 mm in diameter) with Ar + N2 mixed gas. Total gas pressure during sputtering (P(total)) was 0.4 Pa. The N2 partial pressure-to-total pressure ratio (P(N2)/P(total)), substrate temperature (T(sub)) and rf power (P(rf)) were changed 0.0-0.5, R. T. is similar to 300-degrees-C and 100-300 W, respectively. The microstructure of the films was studied by transmission electron microscopy. A deposition rate decreased with increasing P(N2)/P(total) and decreased drastically when P(N2)/P(total) increased above a threshold value. The threshold value was about 0.25 at P(rf) 300 W. It was shown that the films prepared at above the threshold value were gold colored and had TiN structure. Although a microstructure was constructed by fine grains, the gold colored film showed strong preferred orientation, which was (001) TiN//(001) NaCl. The higher substrate temperature and the higher applied rf power resulted in the larger grain sized film. It was considered that growth process of TiN films was based on a three dimensional nucleation. Unfortunately, reproducibility was not so good, it was suggested that (001)TiN single crystal films were able to grow on (001)NaCl at 300-degrees-C, which was lower than the reported epitaxial temperature of TiN films on MgO single crystal.

Raman spectroscopy should be a useful technique for a nondestructive characterization of surface layers on metals. In this study, Raman spectroscopy has been used to examine oxide layers formed on stainless steels in air at elevated temperatures. Specimens of commercial austenitic stainless steels (SUS304, SUS316 and SUS310S) were prepared by polishing with #1200 emery paper and degreasing in an ultrasonic bath of acetone. Oxidations were carried out in a preheated furnace at 573-1073 K for 1.8-3600 ks. Raman spectra were obtained from these oxide layers formed on stainless steels. Auger depth analysis was also used to study the oxide layers. When oxidation temperature was below about 873 K, it was clarified that iron oxides such as Fe2O3 and Fe3O4 were formed. On the other hand, the surface oxide layers at above 873 K were composed of Cr2O3, MnCr2O4 and FeCr2O4. The composition of stainless steels was less dependent on these oxidation behavior. The thickness of the oxide layer formed at 1073 K for 7.2 ks was estimated at about 400 nm by Auger depth profiling. From a comparison of the Raman spectra with Auger depth profiling, it was concluded that the Raman spectra measured in this study were obtained from the whole layer on the surface oxide film. Therefore, Raman spectroscopy technique can be applied to the characterization of the oxide layers up to about 1-mu-m thickness formed on stainless steels.

The atomic structure of amorphous Si1-xCx(a-Si1-xCx) films was studied by transmission electron microscopy, and with the measurements of IR absorption, electron spin resonance and electrical conductivity. The films were prepared by r.f. planar magnetron sputtering with composite targets which consist of silicon and graphite. It was shown from transmission electron diffraction and IR absorption measurements that the carbon atoms occupy substitutional sites of the a-Si network uniformly in the range of 0&lt x≤0.38, and that there exist clusters of threefold carbon and of fourfold silicon and carbon in the range of 0.38&lt x≤1.0. The temperature dependence of conductivity showed that variable range hopping conductions is predominant in a-Si1-xCx film at 77-300 K. Furthermore, the density of states near the Fermi energy N(EF) was calculated theoretically from the temperature dependence of conductivity. The results showed that most of the states near the Fermi energy are made by the dangling bonds in the range 0≤x≤0.38 and that they are made not only by the dangling bonds but also by the other defects in the range 0.38&lt x≤1.0. © 1989.