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N2 mixtures
Cla;~if;cd abstracts 7214--7221 retain the special properties of the DLC material. The purity and structure of the films will be discussed from the point of view of high kinetic energy of the atoms on the surface and the additional kinetic energy supplied to the film by ion-assisted deposition through the simultaneous bombardment by 40 200 eV argon ions. S Aisenberg, J Vac Sci Technol, A8, 1990, 2150 2154. 23 7214. Characterization and growth mechanisms of boron nitride films synthesized by ion-beam-assisted deposition We have studied boron nitride films deposited at room temperature by ion-beam-assisted deposition in an uhv apparatus, with ion accelerating voltages ranging between 0.25 and 2 kV. By using complementarily #~ situ Auger electron spectrometry and ex situ nuclear analyses to determine the respective surface and bulk N concentrations in the deposited films, we were able to identify the different phases of the mechanism leading to the nitridation of evaporated boron by nitrogen ions. For low nitrogen/ boron flux ratios, the incorporation of nitrogen seems to be only governed by ion implantation, and, with respect to the depth of the deposit, the surface is found largely depleted in nitrogen, while the N-incorporation yield remains close to one whatever the ion energy. Such a behavior is well verified as long as a critical bulk nitrogen concentration close to 5.5 x 10-': cm 3 has not been achieved. For concentrations greater than this, superstoichiometric material is obtained up to a saturation which corresponds to a bulk N incorporation ranging from 6 to 7 x 10:2 cm ). Further increase of the N/B flux ratio induces a strong diffusion process from N-rich bulk to N-depleted surface, which results in the nitridation of surface boron atoms and a loss of nitrogen by sputtering or desorption. The density measurements seem to indicate that the synthesized phase is close to h-BN. However, the density of B-rich layers ([N]/[B] ~ 0.2 0.3) is found to be very close to that calculated for a mixture of pure boron and c-BN. The transparency and microhardness of the synthesized BN have satisfying values for its application as a wear-resistant optical coating, but it is not c-BN. O Burat et al, J Appl Phys, 68, 1990, 2780 2790. 23 7215. The dissociation of transition metal oxides under exposure to low energy ions The results of an investigation of how transition metal (Ti, Zr, Nb, HI', Ta) oxides and their mixtures dissociate under the action of 3 5 keV Ar ions are reported. Analysis of the dissociation of pure oxides allows us to suggest that the composition of the resulting surface region, after sputtering, depends upon the reverse chemical reaction between the metal and oxygen atoms formed during the collision cascade process. The importance of the reverse chemical reaction is demonstrated in separate experiments using transition metal oxide mixtures. L A Vasilyev et al, Vacuum, 41, 1990, 43 45. 23 7216. Oxidation kinetics of plasma-enhanced chemical vapor deposition silicon nitride films deposited from SiH4]NH3[NF3[N2mixtures Fluorinated silicon nitride films have been deposited by plasma-enhanced chemical vapor deposition (PECVD) varying the relative [NF3] / ([NH3] + [NF3]) flow ratio in the range 0 1. The as-deposited films show an increase in the NH radicals and a decrease in thc Sill radicals when the flow ratio increases above 0.5. In addition, these films are very unstable in hot water as well as in normal air atmospheres. The oxidation kinetics have been explained in terms of a direct oxidation reaction of the silicon nitride lattice accompanied by the formation of fluorinated complexes which also react with moisture to give finally SiO:. C G6mez-Aleixandre et al, J Vac Sci Technol, B8, 1990, 540 543. 23 7217. Plasma deposited silicon nitride encapsulant for rapid thermal annealing of St-implanted GaAs Silicon nitride films were deposited by the plasma-enhanced chemical vapor deposition (PECVD) method in a silane and nitrogen atmosphere as encapsulants for rapid thermal annealing of St-implanted GaAs. The deposition rate and refractive index of PECVD silicon nitride films were measured with varying radio-frequency (r0 power, chamber pressure, N:/SiH4 ratio, and substrate temperature. A wide range of deposition parameters was used, and this range of rf power dependence has not been previously reported. S Lee and A Gopinath, J Vac Sci Technol, B8, 1990, 402 406. 572
23 7218. The deposition of diamond films by filament techniques Several important aspects of the vapor deposition of diamond thin films by hot filament associated chemical vapor deposition (CVD) are described. This deposition technique is economical and scalable to large areas, ftowever, practical difficulties such as deformation of the filament and its relatively short lifetime often obscure these advantages. Techniques to overcome these difficulties have been developed. Straight rhenium wires, mounted under tension are used for the activation of the precursor gas mixture. The effects of wire diameter, temperature, length, and spacing on the thickness distribution and deposition rate of the diamond films have been determined. For high quality and large area diamond films, deposition rates arc generally very low and it is often necessary to overcome a nucleation barrier. The use of submicron diamond powder to provide the necessary nucleation sites is discussed. g Jansen et al, J Vac Sci Technol, A8, 1990, 3785 3790.
23 7219. Formation of cubic boron nitride films by arc-like plasma-enhanced ion plating method Thin cubic boron nitridc (cBN) lihns were synthesized at 3 5 0 C on various substrates such as silicon, stainless steel, TiN-coated WC Co and WC Co by means of an arc-like plasma-enhanced ion plating process. In this process, polycrystalline cBN films were obtained at deposition rates of 0.004 0.03/lm rain ~. The ir spectra showed strong absorption at 1050 cm ~, indicating cubic structure of the dcposited film. The electron diffraction patterns also showed the cubic structurc, with a lattice parameter of 3.63/~. It is inferred thai ion bombardment during film growth plays an important role in the l~rmation of cBN films. The cBN films deposited in this process had a high compressive stress of 4 x l() ~'~ dyn cm ~, which is significantly greater than the value of hard amorphous boron nitride (iBN) films, 1.6 x 10H~dyn e m : . The internal strcss ofcBN tilms was greatly reduced if iBN was used as a buffer layer between cBN and substrate. T Ikeda et al, J Vac Sci Technol, A8, 1990, 3168 3174.
23 7220. Nitridation induced on metal surface by Art-ion impact under 82 atmosphere Nitridation of surfaces has been examined by bombarding transition metals with 0.3 8 keV Ar ' -ions (4 llA cm 2) under a nitrogen atmosphere (I x 10 ~ Pa) at room temperature. The surface N: Metal ratio determined by XPS increased with irradiation time at lower fluences and reached a plateau at higher fluences. Using reaction kinetics for the nitridation of a Ti target allows the rate of nitride formation, defined as the number of TiN molecules produced by one incident ion, to be determined. For this procedure it is estimated to be about I7. The saturation value of the N : Me ratio for various metal targets increased with decreasing Gibbs tkee energy for the thermochemical formation of a nitride. This suggests that the dominant mechanisms for ion-induced nitridation are the thermochemical processes which occur at the bombardment area of the target surfacc. T A Sasaki et al, Vacuum, 41, 1990. 185 187.
23 7221. Removal of the process-induced fluorine associated to chemical vapor deposition of tungsten onto a polycrystalline silicon gate structure by beat treatment in a hydrogen-containing atmosphere Tungsten was deposited from a gas mixture of hydrogen and tungsten hexafluoride onto a polycrystalline silicon gate structure in a chemical vapor deposition system. During the deposition process fluorine was also deposited as an undesired impurity. In order to remove the fluorine, heat treatments in the temperature range 550- 1050C were performed in a hydrogen atmosphere. By this treatment it is possible to form volatile hydrofluoric acid and hence remove fluorine from the structure. Nuclearresonance-broadening technique and secondary ion mass spectrometry were used for the analysis of fluorine. Fluorine was detected in all the samples except for the sample heat treated at 1050 C. Moreover, etching of the polycrystallinc silicon was observed. The gettering of fluorine, the etching of silicone and the observed formation of tungsten disilicide at 650"C are discussed with respect to conceivable mechanisms. A thermodynamic study supporting the interpretations is also included. Th Eriksson et al, J AppI Ph_vs, 68, 1990, 2112 2120.
23 7218. The deposition of diamond films by filament techniques Several important aspects of the vapor deposition of diamond thin films by hot filament associated chemical vapor deposition (CVD) are described. This deposition technique is economical and scalable to large areas, ftowever, practical difficulties such as deformation of the filament and its relatively short lifetime often obscure these advantages. Techniques to overcome these difficulties have been developed. Straight rhenium wires, mounted under tension are used for the activation of the precursor gas mixture. The effects of wire diameter, temperature, length, and spacing on the thickness distribution and deposition rate of the diamond films have been determined. For high quality and large area diamond films, deposition rates arc generally very low and it is often necessary to overcome a nucleation barrier. The use of submicron diamond powder to provide the necessary nucleation sites is discussed. g Jansen et al, J Vac Sci Technol, A8, 1990, 3785 3790.
23 7219. Formation of cubic boron nitride films by arc-like plasma-enhanced ion plating method Thin cubic boron nitridc (cBN) lihns were synthesized at 3 5 0 C on various substrates such as silicon, stainless steel, TiN-coated WC Co and WC Co by means of an arc-like plasma-enhanced ion plating process. In this process, polycrystalline cBN films were obtained at deposition rates of 0.004 0.03/lm rain ~. The ir spectra showed strong absorption at 1050 cm ~, indicating cubic structure of the dcposited film. The electron diffraction patterns also showed the cubic structurc, with a lattice parameter of 3.63/~. It is inferred thai ion bombardment during film growth plays an important role in the l~rmation of cBN films. The cBN films deposited in this process had a high compressive stress of 4 x l() ~'~ dyn cm ~, which is significantly greater than the value of hard amorphous boron nitride (iBN) films, 1.6 x 10H~dyn e m : . The internal strcss ofcBN tilms was greatly reduced if iBN was used as a buffer layer between cBN and substrate. T Ikeda et al, J Vac Sci Technol, A8, 1990, 3168 3174.
23 7220. Nitridation induced on metal surface by Art-ion impact under 82 atmosphere Nitridation of surfaces has been examined by bombarding transition metals with 0.3 8 keV Ar ' -ions (4 llA cm 2) under a nitrogen atmosphere (I x 10 ~ Pa) at room temperature. The surface N: Metal ratio determined by XPS increased with irradiation time at lower fluences and reached a plateau at higher fluences. Using reaction kinetics for the nitridation of a Ti target allows the rate of nitride formation, defined as the number of TiN molecules produced by one incident ion, to be determined. For this procedure it is estimated to be about I7. The saturation value of the N : Me ratio for various metal targets increased with decreasing Gibbs tkee energy for the thermochemical formation of a nitride. This suggests that the dominant mechanisms for ion-induced nitridation are the thermochemical processes which occur at the bombardment area of the target surfacc. T A Sasaki et al, Vacuum, 41, 1990. 185 187.
23 7221. Removal of the process-induced fluorine associated to chemical vapor deposition of tungsten onto a polycrystalline silicon gate structure by beat treatment in a hydrogen-containing atmosphere Tungsten was deposited from a gas mixture of hydrogen and tungsten hexafluoride onto a polycrystalline silicon gate structure in a chemical vapor deposition system. During the deposition process fluorine was also deposited as an undesired impurity. In order to remove the fluorine, heat treatments in the temperature range 550- 1050C were performed in a hydrogen atmosphere. By this treatment it is possible to form volatile hydrofluoric acid and hence remove fluorine from the structure. Nuclearresonance-broadening technique and secondary ion mass spectrometry were used for the analysis of fluorine. Fluorine was detected in all the samples except for the sample heat treated at 1050 C. Moreover, etching of the polycrystallinc silicon was observed. The gettering of fluorine, the etching of silicone and the observed formation of tungsten disilicide at 650"C are discussed with respect to conceivable mechanisms. A thermodynamic study supporting the interpretations is also included. Th Eriksson et al, J AppI Ph_vs, 68, 1990, 2112 2120.