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Glow discharge characteriztics when magnetron sputtering copper in different plasma atmospheres operated at low input power
Classified abstracts 6 5 1 6 - 6 5 2 3
yields has been investigated under various surface conditions. Three different models of rough surfaces are employed: (1) the rough surface with randomly distributed vacancies at the topmost layer, (2) the rectangular-step surface, and (3) the oblique-step surface with the same inclined angle as the angle of incidence. It is found that the ion-bombardmentinduced surface roughness greatly influences the bombarding-angle dependences of both the sputtering yield and the particle reflection coefficient. Due to the surface roughness the surface scattering is reduced and this effect results in the shift of the bombarding angle for the maximum sputtering yield to a higher angle of incidence. Y Yamamura et al, Radiat Effects, 103, 1987, 25~43. 21 6516. Angular distributions of sputtered atoms from ion-bombarded surfaces Using the ACAT code, angular distributions of sputtered atoms have been investigated under various surface conditions. Two different models of rough surfaces are employed, i.e., (1) the rough surface with randomly distributed vacancies at the topmost layer, (2) the rectangular-step surface. Computer simulations have been performed for 1.05 keV Ar ions on Ta target. It is found that the ion-bombardment-induced surface roughness very much influences the angular distributions of sputtered atoms for grazing angle of incidence. Ion-bombardment induced-surface roughness plays two important roles for angular distributions of sputtered atoms at grazing angles of incidence: (1) Due to the surface roughness the surface scattering is reduced, and so the velocity distribution of recoil atoms in collision cascades near the surface become more isotropic, which leads to the cosine-like distributions. (2) Due to surface roughness the average distance of two surface atoms is larger than that of unirradiated surface, and so the shadowing effect and the periodicity of surface atoms is less problem. As a result, the preferential angle of ejection from the ion-bombardment-induced rough surface can roughly be estimated by the direct knock-out model. Y Yamamura et al, Radiat Effects, 105, 1987, 31-41. 21 6517. The preparation and characterization of titanium boride films Metal boride films have been shown to be useful in many applications where refractory properties are required. Potential microelectronics applications include use as a diffusion barrier and as a boron diffusion source. In this study, the boron outdiffusion behavior of several compositions of titanium boride films was investigated. TiB2. j films did not react with the silicon substrate upon annealing up to 1092°C, but TiB films reacted with silicon at elevated temperatures, apparently to form a titanium silicide. The surface concentration of boron in the silicon substrate increased as the boron-to-titanium ratio in the boride film increased. The boron diffusivities obtained from TiB2.~ and TiB2.9 sources are greater than values observed for other types of boron diffusion source when analyzed with the vacancy model. Resistivity studies showed that thicker titanium diboride films had lower resistivities than thinner films when annealed above 1000°C. Post-anneal film stress was independent of anneal temperature above 900°C. The resistivity and film stress values obtained for titanium diboride films were similar to the values observed for refractory metal silicides. James G Ryan et al, Thin Solid Films, 153, 1987, 329 339. 2l 6518. Energy flux onto an l~V magnetron surface The energy flux onto an R~ magnetron electrode surface was measured by a non-perturbative calorimetric method in Ar, CF4, C2F 6, CHF3 and C3Fs discharges. It was found that about 40% to 80% of the input RF power was dissipated on the magnetron electrode surface. The energy flux is 15% to 50% higher in argon than that in the fluorocarbons. When the sheath voltage is greater than 100 V, energy flux is mainly contributed by ion kinetic energy, and Q oc nd V~c[oc (RE power) t2, where nl is the ion density and VDcis the DC potential of the capacitively coupled magnetron electrode. For the sheath voltage less than 100 V, radiation, e l e c t r o ~ ion wall recombination, and neutral relaxation processes have to be considered. It is also found that the anomalous diffusion, presumably due to drift-type turbulence, affects the cross-field energy flux onto the electrode surface. I Lin et al, J Phys D: Appl Phys, 21, 1988, 951 955. 21 6519. Predicting thin-film stoichiometry in reactive sputtering The electrical, optical, and mechanical properties of a compound film
depend strongly on the composition of the film. Therefore, it is interesting to study a wide variety of compositions of many new compound materials. Reactive sputtering is a widely used technique to produce compound thin films. With this technique it is possible to fabricate thin films with different compositions. However, it has not yet, to any great extent, been possible to predict the composition of the sputtered film. In this article we will present a model that enables us to predict both sputtering rate and film composition during reactive sputtering. The results point out that there exists a very simple linear relationship between processing parameters for maintaining constant thin-film composition in the reactive sputtering process. Based on these results, it is possible for the first time to combine information of both sputtering rate and film composition into the same graphical representation. Access to this new and simple graphical representation may eliminate much of the "trial and error" work that earlier has been associated with the reactive sputtering process. S Berg et al, Jappl Phys, 63, 1988, 887 891. 21 6520. Preparation and properties of the de reactively sputtered tungsten oxide films Preparation and properties of the dc reactively sputtered tungsten oxide films have been investigated in relation to the oxygen concentration in sputtering atmosphere. The films with 1500-20,700 /~ thickness were deposited on the glass substrates maintained at 200°C by dc reactive sputtering from a metallic tungsten target under a constant operating pressure of 6.5 x 10 -2 Torr in Ar-1%-30% 02 gas mixture. The films formed in an Ar-3% 20% Oz gas mixture are crystalline WO3, and have an electrical resistivity of 107-10" fl cm which is dependent on the oxygen concentration of the sputtering atmosphere. These films have a spectral transmittance above 80% in the visible and near-infrared regions, and optical band gap of the films ranges from 3.15 to 2.98 eV, depending on the oxygen concentration. Densities of the film deposited in Ar-3% 02 and in Ar-20% 02 gas mixtures are 5.85 g/cm 3 and 6.65 g/cm 3, respectively. Electrochemichromic properties of the transparent-crystalline WO3 films were studied using asymmetric cells, and were found to be dependent on the crystal orientation of the films. The films with the orientation of WO3 (020) and WO3 (021) formed in an Ar-3%~6% 02 gas mixture have a very good electrochromic property, and the cells composed of the crystalline WO3 films have a higher coloration rate than the cells composed of the vacuum-evaporated amorphous film. The films with the orientation o f W O 3 (001) and WO3 (021) formed in an Ar-8% 20% 02 gas mixture were found to have a poor electrochromic property. H Kaneko et al, Jappl Phys, 63, 1988, 510-517. 21 6521. Glow discharge characteristics when magnetron sputtering copper in different plasma atmospheres operated at low input power A study has been made of the glow discharge characteristics of a magnetron used for sputtering copper in different gases: Ar, A r + N 2 and Ar+O2. The effects of gas type, gas pressure and the presence of water vapour on the glow discharge characteristics are discussed and interpreted from the magnetron ~ Vcurves. Information on glow discharge resistance as well as the effects of copper nitride and copper oxide formation are presented. The results showed that neither hysteresis nor sharp transitions are observed at all values of input power chosen. A Rizk et al, Vacuum, 38, 1988, 93-95. 21 6522. Characterization of MoSez thin films The influence of sputtering and annealing on the properties of MoSe2 films was investigated by scanning electron microscopy, electron micro probe analysis, X-ray photoelectron spectroscopy (XPS), X-ray analysis, optical absorption and electrical resistivity measurements. It was found that stoichiometric thin films are obtained after appropriate annealing. The c axis orientation depends strongly on the thin film composition before annealing. The crystallite size varies between 10 and 200 nm. The optical gaps were determined to be almost equal to those of MoSe2 single crystals. The chemical shifts of the XPS lines were found to be in good agreement with those of a stoichiometric powder reference. A Mallouky and J C Bernede, Thin Solid Films, 158, 1988, 285-298. 21 6523. A quasi-direct-current sputtering technique for the deposition of dielectrics at enhanced rates A new sputterng process with particular advantages for the deposition of dielectric films has been developed. Low-frequency power is applied 497
yields has been investigated under various surface conditions. Three different models of rough surfaces are employed: (1) the rough surface with randomly distributed vacancies at the topmost layer, (2) the rectangular-step surface, and (3) the oblique-step surface with the same inclined angle as the angle of incidence. It is found that the ion-bombardmentinduced surface roughness greatly influences the bombarding-angle dependences of both the sputtering yield and the particle reflection coefficient. Due to the surface roughness the surface scattering is reduced and this effect results in the shift of the bombarding angle for the maximum sputtering yield to a higher angle of incidence. Y Yamamura et al, Radiat Effects, 103, 1987, 25~43. 21 6516. Angular distributions of sputtered atoms from ion-bombarded surfaces Using the ACAT code, angular distributions of sputtered atoms have been investigated under various surface conditions. Two different models of rough surfaces are employed, i.e., (1) the rough surface with randomly distributed vacancies at the topmost layer, (2) the rectangular-step surface. Computer simulations have been performed for 1.05 keV Ar ions on Ta target. It is found that the ion-bombardment-induced surface roughness very much influences the angular distributions of sputtered atoms for grazing angle of incidence. Ion-bombardment induced-surface roughness plays two important roles for angular distributions of sputtered atoms at grazing angles of incidence: (1) Due to the surface roughness the surface scattering is reduced, and so the velocity distribution of recoil atoms in collision cascades near the surface become more isotropic, which leads to the cosine-like distributions. (2) Due to surface roughness the average distance of two surface atoms is larger than that of unirradiated surface, and so the shadowing effect and the periodicity of surface atoms is less problem. As a result, the preferential angle of ejection from the ion-bombardment-induced rough surface can roughly be estimated by the direct knock-out model. Y Yamamura et al, Radiat Effects, 105, 1987, 31-41. 21 6517. The preparation and characterization of titanium boride films Metal boride films have been shown to be useful in many applications where refractory properties are required. Potential microelectronics applications include use as a diffusion barrier and as a boron diffusion source. In this study, the boron outdiffusion behavior of several compositions of titanium boride films was investigated. TiB2. j films did not react with the silicon substrate upon annealing up to 1092°C, but TiB films reacted with silicon at elevated temperatures, apparently to form a titanium silicide. The surface concentration of boron in the silicon substrate increased as the boron-to-titanium ratio in the boride film increased. The boron diffusivities obtained from TiB2.~ and TiB2.9 sources are greater than values observed for other types of boron diffusion source when analyzed with the vacancy model. Resistivity studies showed that thicker titanium diboride films had lower resistivities than thinner films when annealed above 1000°C. Post-anneal film stress was independent of anneal temperature above 900°C. The resistivity and film stress values obtained for titanium diboride films were similar to the values observed for refractory metal silicides. James G Ryan et al, Thin Solid Films, 153, 1987, 329 339. 2l 6518. Energy flux onto an l~V magnetron surface The energy flux onto an R~ magnetron electrode surface was measured by a non-perturbative calorimetric method in Ar, CF4, C2F 6, CHF3 and C3Fs discharges. It was found that about 40% to 80% of the input RF power was dissipated on the magnetron electrode surface. The energy flux is 15% to 50% higher in argon than that in the fluorocarbons. When the sheath voltage is greater than 100 V, energy flux is mainly contributed by ion kinetic energy, and Q oc nd V~c[oc (RE power) t2, where nl is the ion density and VDcis the DC potential of the capacitively coupled magnetron electrode. For the sheath voltage less than 100 V, radiation, e l e c t r o ~ ion wall recombination, and neutral relaxation processes have to be considered. It is also found that the anomalous diffusion, presumably due to drift-type turbulence, affects the cross-field energy flux onto the electrode surface. I Lin et al, J Phys D: Appl Phys, 21, 1988, 951 955. 21 6519. Predicting thin-film stoichiometry in reactive sputtering The electrical, optical, and mechanical properties of a compound film
depend strongly on the composition of the film. Therefore, it is interesting to study a wide variety of compositions of many new compound materials. Reactive sputtering is a widely used technique to produce compound thin films. With this technique it is possible to fabricate thin films with different compositions. However, it has not yet, to any great extent, been possible to predict the composition of the sputtered film. In this article we will present a model that enables us to predict both sputtering rate and film composition during reactive sputtering. The results point out that there exists a very simple linear relationship between processing parameters for maintaining constant thin-film composition in the reactive sputtering process. Based on these results, it is possible for the first time to combine information of both sputtering rate and film composition into the same graphical representation. Access to this new and simple graphical representation may eliminate much of the "trial and error" work that earlier has been associated with the reactive sputtering process. S Berg et al, Jappl Phys, 63, 1988, 887 891. 21 6520. Preparation and properties of the de reactively sputtered tungsten oxide films Preparation and properties of the dc reactively sputtered tungsten oxide films have been investigated in relation to the oxygen concentration in sputtering atmosphere. The films with 1500-20,700 /~ thickness were deposited on the glass substrates maintained at 200°C by dc reactive sputtering from a metallic tungsten target under a constant operating pressure of 6.5 x 10 -2 Torr in Ar-1%-30% 02 gas mixture. The films formed in an Ar-3% 20% Oz gas mixture are crystalline WO3, and have an electrical resistivity of 107-10" fl cm which is dependent on the oxygen concentration of the sputtering atmosphere. These films have a spectral transmittance above 80% in the visible and near-infrared regions, and optical band gap of the films ranges from 3.15 to 2.98 eV, depending on the oxygen concentration. Densities of the film deposited in Ar-3% 02 and in Ar-20% 02 gas mixtures are 5.85 g/cm 3 and 6.65 g/cm 3, respectively. Electrochemichromic properties of the transparent-crystalline WO3 films were studied using asymmetric cells, and were found to be dependent on the crystal orientation of the films. The films with the orientation of WO3 (020) and WO3 (021) formed in an Ar-3%~6% 02 gas mixture have a very good electrochromic property, and the cells composed of the crystalline WO3 films have a higher coloration rate than the cells composed of the vacuum-evaporated amorphous film. The films with the orientation o f W O 3 (001) and WO3 (021) formed in an Ar-8% 20% 02 gas mixture were found to have a poor electrochromic property. H Kaneko et al, Jappl Phys, 63, 1988, 510-517. 21 6521. Glow discharge characteristics when magnetron sputtering copper in different plasma atmospheres operated at low input power A study has been made of the glow discharge characteristics of a magnetron used for sputtering copper in different gases: Ar, A r + N 2 and Ar+O2. The effects of gas type, gas pressure and the presence of water vapour on the glow discharge characteristics are discussed and interpreted from the magnetron ~ Vcurves. Information on glow discharge resistance as well as the effects of copper nitride and copper oxide formation are presented. The results showed that neither hysteresis nor sharp transitions are observed at all values of input power chosen. A Rizk et al, Vacuum, 38, 1988, 93-95. 21 6522. Characterization of MoSez thin films The influence of sputtering and annealing on the properties of MoSe2 films was investigated by scanning electron microscopy, electron micro probe analysis, X-ray photoelectron spectroscopy (XPS), X-ray analysis, optical absorption and electrical resistivity measurements. It was found that stoichiometric thin films are obtained after appropriate annealing. The c axis orientation depends strongly on the thin film composition before annealing. The crystallite size varies between 10 and 200 nm. The optical gaps were determined to be almost equal to those of MoSe2 single crystals. The chemical shifts of the XPS lines were found to be in good agreement with those of a stoichiometric powder reference. A Mallouky and J C Bernede, Thin Solid Films, 158, 1988, 285-298. 21 6523. A quasi-direct-current sputtering technique for the deposition of dielectrics at enhanced rates A new sputterng process with particular advantages for the deposition of dielectric films has been developed. Low-frequency power is applied 497