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7182. Properties of W-N and Mo-N films prepared by reactive sputtering
Classified abstracts 7174-7182
sputtered LaB6 films was (100) which is the orientation of lower work function (2.4-2.5 eV) in LaB6 crystals. T Kajiwara et al, Vacuum, 41, 1990, 1224-1228. 21 7174. Sputtered magnetic films for rigid disk production A description of the magnetic properties of full-sputtered rigid disks is given, such as those used in modern Winchester drives. Using a modular in-line system, and high rate magnetron sputtering, a layer stack of C ~ CoNiCr-C was prepared on a large area, industrial scale. The influence of layer thicknesses and process parameters has been investigated. The coercivity saturates when the Cr underlayer is thick. High squareness of the hysteresis loop is achieved with thin layers. The crystalline properties have been measured as well. The epitaxial growth of the Co on top of the Cr (110) plane plays a key role in the determination of good magnetization properties. B Cord and W MaaB, Vacuum, 41, 1990, 1176-1178. 21 7175. Preparation of AIN films by planar magnetron sputtering system with facing two targets A planar magnetron sputtering system with facing two targets was presented and the discharge characteristics were examined for reactive sputtering of A1 in N2 gas atmosphere. It was found that the reactive sputtering is possible even at a low gas pressure such as 5 x 10 4 tort. At a substrate temperature of 250°C, all films obtained were c-axis oriented films where the c-axis is normal to the substrate surface. Even at a substrate temperature of T = 50°C, slightly degraded c-axis oriented films were obtained compared with those at 250°C. K Tominaga, Vacuum, 41, 1990, 1154-1156. 2! 7176. Computer experiments of initial growth kinetics of vacuum-deposited thin films The formation process of thin films is studied by the Monte Carlo method. The reason for the occurrence of the three different growth modes, i.e. the Volme~Weber mode, the Frank van der Merwe mode and the StanskiKrastanov mode, is discussed in relation to the parameters used in the Morse potential. It is suggested that the growth mode is mainly determined by the energy parameters rather than the experimental conditions of the film growth, except for the Stranski--Krastanov mode. S Ozawa and Y Sasajima, Vacuum, 41, 1990, 1109-1110. 21 7177. Superconducting thin films of n-type copper oxide prepared by rf magnetron sputtering Thin films of electron-doped copper oxide superconductor were prepared by rf magnetron sputtering and subsequent annealing processes on the surface of SRTiO3 substrates. These thin films showed a highly crystalline structure and a sharp superconducting transition at 23 K with a transition width of less than 1 K. Using these high quality thin films, the basic superconducting characteristics, such as reduction process, electronic and magnetic data, electron spectroscopy, and optical properties, were reported. K Setsune et al, Vacuum, 41, 1990, 864-866. 21 7178. Large-area industrial vacuum coating in the 1990s Large-area vacuum coating is defined as vacuum processing of thin films and substrate surfaces which are significantly larger in area than integrated circuits. Historically, applications of large-area vacuum coating technology have included roll-to-roll metallized polymer films for capacitors, decorative packaging, and window glazing films; and coatings on rigid discrete substrates for decorative fixtures, precision mirrors and lenses, and antiglare CRT screens. New markets, evolving technologies, and societal concerns will influence the direction and growth of largearea industrial vacuum coating technology in the 1990s. With the increase of two-worker households and the corresponding popularity of convenience cooking, food packaging materials which provide extended shelf life and enhance microwave preparation will be a growing market. More demanding requirements for recording media, medical applications, and space technology will generate new commercial opportunities for largearea vacuum coating. And concerns relating to control of toxic byproducts of industrial coating, plating and etching processes will cast large-area vacuum processing in an attractive new light. P R Johansen, J Vac Sci Technol, A8, 1990, 2798-2801.
• ,,
21 7179. A comparison of SiO2 planarization layers by hollow cathode enhanced direct current reactive magnetron sputtering and radio frequency magnetron sputtering SiO2 films have been prepared by hollow cathode enhanced dc reactive magnetron sputtering [J J Cuomo and S M Rossnagel, J Vac Sci Technol, A4, 393 (1986)] and for comparison by rf magnetron sputtering from an SiO2 target. The hollow cathode arc source is used in a triode configuration with the magnetron. This configuration allows sputtering to take place at pressures as low as 5 x 10 4 tort, as well as sputtering of the oxide without arcing below ~ 600 V. These films were investigated as a dielectric planarization layer for Josephson (superconducting) devices. To this end, film deposition parameters (02 flow rate, Ar partial pressure, magnetron target voltage, hollow cathode current) have been related to film deposition rate, index of refraction, measured by ellipsometry, stoichiometry, measured by X-ray photoelectron spectroscopy (XPS), and coating conformity as measured by electron microscopy. A similar set of experiments was performed for the rf sputtered films. The relationships were investigated using factorial experiment design. D F Dawson-Elli et al, J Vac Sci Technol, A8, 1990, 1294-1298. 21 7180. Beam parameter effects on magnetic properties of sputtered amorphous Fe40Ni4oBisSis and Fe4oCo4oB15Si5 films Amorphous films were deposited onto fused quartz by ion beam sputter deposition to examine possible alternatives to existing polycrystalline microwave materials. Ion beam parameters were systematically varied to determine the dependence of film magnetic properties on beam conditions. Chemical composition of representative films were confirmed using Auger electron spectroscopy and Rutherford backscattering spectroscopy. Amorphousness was confirmed by X-ray diffraction analysis, and film thickness was determined by surface profilometer trace. Film magnetic properties were measured by vibrating sample magnetometer and ferromagnetic resonance techniques. It was found that films deposited under higher beam energies showed the lowest eoercivities and anisotropy fields. Saturation magnetization values remained largely unaffected by beam parameter variation. Evidence suggests vacuum base pressure plays a significant role in film magnetic properties. Improvement of the films' soft magnetic properties with increased beam energy may be attributed to reductions in trapped impurities resulting from increased deposition rates. The resulting films display promising properties for microwave magnetic applications. V G Harris et al, J Vac Sci Technol, A8, 1990, 1325 1329. 21 7181. Characterization of sputter-deposited ZrBxOy films ZrBxOy films for optical durable coating application were deposited by reactive dc magnetron sputtering of Zr-B alloy target on soda-lime silica glass substrate without intentional heating. Effect of boron content on film properties was investigated. The refractive index of the film was decreased from 2.1 to 1.69 corresponding to the increase of B203 content from 0 to 64 mol%. The films containing more than 13 mol% B20 3 fraction were amorphous and showed remarkably improved mechanical durability compared with ZrO2 film. More than 51 mol% B203 content resulted in degrading of chemical durability. Measurement of mechanical properties was carried out together with characterization on crystalline structure and chemical binding state. J Ebisawa et al, J Vac Sci Technol, A8, 1990, 1335 1339. 21 7182. Properties of W-N and Mo-N films prepared by reactive sputtering The structure and properties of W - N films up to 22 #m thick prepared by a reactive dc magnetron sputtering process are reported. It has been found that the properties of the deposited films not only depend on the nitrogen partial pressure in the argon-nitrogen gas mixtures but also on total gas pressure and input power during sputtering. The rate of deposition decreased with increase of nitrogen partial pressure, but was higher at higher total pressure and input power. The resistivity increased with nitrogen partial pressure but was lower at lower total gas pressure and higher input power. The hardness of W N films could be varied from 600 to 3000 kg mm 2 depending on sputtering conditions. The hardness, in general, increased with nitrogen partial pressure with higher value at higher total pressure and input power. X-ray diffraction did not indicate presence of nitride phases when the content of nitrogen in the argon nitrogen gas mixtures during sputtering was below 10%, and the total gas pressure was <40 mtorr. WzN was observed when the nitrogen 567
Classiqed abstracts 7183-7191
content was over 30% and also when the nitrogen content was over 10% and total gas pressure was over 40 mtorr. These results are consistent with composition determined by the microprobe measurements. Similar studies on Mo N films made by dc and rf magnetron reactive sputtering methods are reported. Hardness values for the Mo N films of more than 2200 kg m m 2 have been observed. K K Shih and D B Dove, J Vac Sci Technol, A8, 1990, 1359 1363. 21 7183. Low resistivity indium-tin oxide transparent conductive films. I. Effect of introducing H20 gas or H2 gas during direct current magnetron sputtering When an inline sputtering system is used to make conductive transparent ITO film by the direct current (de) magnctron sputtering method, it was found that the partial gas pressure of H 2 0 affected the properties of deposited films. When the substrate temperature is at or below 200< C, the control of H 2 0 partial gas pressure is especially important. Using room temperature substrates, an addition of 2 × I0 ~ torr of H 20 in the sputtering process could form ITO films with good repeatability at a low resistivity of 6.0 x l0 4 Q cm. By adding H 2 0 gas, it was possible to solve the issue of increased resistivity in thicker films. The films with added I t 2 0 gas have H element immersed into the film and have high carrier concentration. Film transmittance stayed constant with or without H 20 gas addition. A similar effect was observed by adding H_~ gas instead of H 2 0 gas. S Ishibashi et al, J Vac Sci Technol, A8, 1990, 1399 1402. 21 7184. Characterization of radio frequency deposited thin carbon films Thin carbon films (2(~50 nm) synthesized from an acetylene rf plasma were characterized by m i c r o - R a m a n spectroscopy, Rutherford backscattering spectroscopy (RBS), forward recoil spectroscopy (FRES), and laser-ablation/Fourier transform mass spectrometry (FTMS). The films were found to be free of any metal impurities by RBS and FTMS. FRES indicated low hydrogen content. Pronounced changes in the R a m a n spectra of films baked in nitrogen suggest structural transformations. The films underwent a transition from a m o r p h o u s to graphitic-like structures after a 24 h bake at 400<'C. Comparison of the R a m a n spectra of the rfdeposited films to those of control films formed from graphite indicated subtle structural differences. L M Siperko et al, J Vac Sci Technol, A8, 1990, 1533 1537. 21 7185. Simulation and measurement of density variation in Mo films sputter deposited over oxide steps A density profile for sputtered metal deposited over a step is generated using SIMulation by BAllistic Deposition (SlMnAD), a two-dimensiomd computer simulation of thin film growth by ballistic deposition of hard disks. By postdeposition etching of a real Mo film deposited over a similar step, regions with high etch rate are identified. As etch rate is relatcd to density, these are assumed to be low density sections, and arc in fact found to agree well with low density regions predicted by the simulations. R N Tait et al, J Vac Sci Technol, A8, 199(I, 1593 1596. 2I 7186. Dielectric properties of rf-sputtered YzO3 thin films Yttrium oxide (Y203) thin films were deposited on indium tin-oxide (lTO)-coaled glass substrates by the if-sputtering method using an Y ~O ~sintered target. The relative dielectric constant ~:~ and the dielectric strength E,t j of the Y20 3 films were studied. It was found that c, and EB, have a m a x i m u m value and a m i n i m u m value, respectively, at 1.3 Pa when the pressure of the sputtering gas, A r + 10% 02, is varied from 0.67 to 9.3 Pa. The X-ray diffraction study showed that the Y 2 0 3 films deposited at 1.3 Pa arc predominantly oriented along the (332) direction and their grain size is the smallest. Ion mass analysis showed impurity diffusion tYom ITO in the films deposited at 1.3 Pa. Furthermore, the dielectric properties of the Y20~ films deposited at 1.3 Pa are related to the structural properties, such as the (332) orientation, grain size, and impurity diffusion. K Onisawa et ai, J Appl Phys, 68, 1990, 719 723. 21 7187. rf diode sputtering A review of rf sputtering principles is presented with reference to recent plasma models and sample calculations. Typical modern sputtering equipment is described and methods of measurement of important pro568
cess variables. Application to the sputtering of Si()~ is described, with data on film properties as a function of bias, rate and oxygen additions. J S Logan, Thin Solid Films, 188, 1990, 307 321. 21 7188. High-rate sputter deposition of SiO2 and TiO~ films for optical applications This paper describes a process to produce SiO: and "l'iO2 films at high rates of deposition by using chemically reactive gases (etch gases). Experiments were conducted using CI> CCI4, CCI~F, CCIF 3, and H 2 mixed individually in Ar and O2 plasma in a magnetron sputtering process. Oxide films were deposited on glass and Si substrates from sputter-etching of St, SiO2, Ti,d and TiO, targets. An attempt was made to understand the mechanism involved in the increased rate of deposition. The results showed that considerable enhancement of the rate of deposition was obtained for SiO3 and TiO2 fihns when sputtered from their pure elemental targets. The enhancement in the rate of deposition ranged between 5 and 30 times over that obtained in a conventional reactive sputtering process. The analysis of the process during sputtering indicated that deposition was accompanied by the formation of volatile chlorides resulting from the chemical etching of the targets. In most cases the coatings had refractive indices close to those of the bulk SiO2 and TiO2, the films were clear and had good resistance to scratching. However, at high concentrations of the etch gases, the optical and scratch properties of the films deteriorated. S S Nandra, J Vac Sci 77,chnol, A8, 1990, 3179 3185. 21 7189. Evaluation of the stopping depth of nonradiative recombination centers in Al~.sGa..sAs by Ar ~ ion beam sputtering by photoluminescence measurements The stopping depth of nonradiativc recombination centers m AI, ~(ia,~ As by Ar + ion beam sputtering was evaluated by photoluminescence (PL) measurements using Al,~Ga0~As/GaAs single heterostructures. Al,~Ga0 ~As layers were sputtered by an Ar ~ ion beam with energies from 0.5 to 3 keV at temperatures l¥om 0 to 3 0 0 C . The PL intensity of the underlying G a A s was measured to detect the damage (nonradiative recombination center). The thickness of the residual AI~)~Ga0,As layer at which the PL intensity of the G a A s began to fall was taken as the stopping depth of nonradiative recombination centers. This depth increased as Ar ~ ion energy increased and sputtering temperature decreased. The depth of damage was roughly proportional to the A r ' ion energy E at about 25 (; for E less than 3 keV. K Akita et al, J Vac Sci Techmd, A8, 1990, 3274 3278. 21 7190. Surface-defect formation in graphite targets during magnetron sputtering Magnetron sputtering of graphite targets is frequently marred by the formation of topographic defects. The defects are either soft with a furry appearance or hard with a stalagmite appearance. The soft defects are often li)und on top of the hard ones, implying a close connection in Ibrmation sequence betwccn the two typcs of defects. The formation mechanism of thc hard defects is related to the presence on thc surface of low sputtering-yield impurities or other types of lattice imperfections, which suppress the erosion induced locally by sputtering, and to porosityinduced asperities. The emergence of the soft defects is ascribed to a growth p h e n o m e n o n involving rcdeposition of carbon from debris and possibly generated in a chemical vapor deposition (CVD) process. The gradual coverage of the target surface by defects causes a steady decrease of the sputtering rate of carbon. Also, the breakup of the soft defects promotes nodular defects in the subsequent growth of the carbon fihn, thus severely degrading the film quality. Remedial measures are devised for limiting the onset of defect formation. C W Chen et al, J Vac Sci Technol, A8, 1990, 3157 3162. 21 7191. Media noise in periodic multilayered magnetic films with perpendicular anisotropy Periodic, finely multilayered thin-film magnetic structures ( ~<200/~) with high in-plane coercivity suitable for longitudinal recording investigations have been fabricated. C o P t , . / P d and CoPt~ ,Cri 7/Pd periodic multilayers can exhibit a perpendicular orientation, originating from surface anisotropy effects, with a magnitude depending on the thickness of the component layers. The perpendicular orientation influences the transition noise, but for the particular systems studied, the results suggest that for
sputtered LaB6 films was (100) which is the orientation of lower work function (2.4-2.5 eV) in LaB6 crystals. T Kajiwara et al, Vacuum, 41, 1990, 1224-1228. 21 7174. Sputtered magnetic films for rigid disk production A description of the magnetic properties of full-sputtered rigid disks is given, such as those used in modern Winchester drives. Using a modular in-line system, and high rate magnetron sputtering, a layer stack of C ~ CoNiCr-C was prepared on a large area, industrial scale. The influence of layer thicknesses and process parameters has been investigated. The coercivity saturates when the Cr underlayer is thick. High squareness of the hysteresis loop is achieved with thin layers. The crystalline properties have been measured as well. The epitaxial growth of the Co on top of the Cr (110) plane plays a key role in the determination of good magnetization properties. B Cord and W MaaB, Vacuum, 41, 1990, 1176-1178. 21 7175. Preparation of AIN films by planar magnetron sputtering system with facing two targets A planar magnetron sputtering system with facing two targets was presented and the discharge characteristics were examined for reactive sputtering of A1 in N2 gas atmosphere. It was found that the reactive sputtering is possible even at a low gas pressure such as 5 x 10 4 tort. At a substrate temperature of 250°C, all films obtained were c-axis oriented films where the c-axis is normal to the substrate surface. Even at a substrate temperature of T = 50°C, slightly degraded c-axis oriented films were obtained compared with those at 250°C. K Tominaga, Vacuum, 41, 1990, 1154-1156. 2! 7176. Computer experiments of initial growth kinetics of vacuum-deposited thin films The formation process of thin films is studied by the Monte Carlo method. The reason for the occurrence of the three different growth modes, i.e. the Volme~Weber mode, the Frank van der Merwe mode and the StanskiKrastanov mode, is discussed in relation to the parameters used in the Morse potential. It is suggested that the growth mode is mainly determined by the energy parameters rather than the experimental conditions of the film growth, except for the Stranski--Krastanov mode. S Ozawa and Y Sasajima, Vacuum, 41, 1990, 1109-1110. 21 7177. Superconducting thin films of n-type copper oxide prepared by rf magnetron sputtering Thin films of electron-doped copper oxide superconductor were prepared by rf magnetron sputtering and subsequent annealing processes on the surface of SRTiO3 substrates. These thin films showed a highly crystalline structure and a sharp superconducting transition at 23 K with a transition width of less than 1 K. Using these high quality thin films, the basic superconducting characteristics, such as reduction process, electronic and magnetic data, electron spectroscopy, and optical properties, were reported. K Setsune et al, Vacuum, 41, 1990, 864-866. 21 7178. Large-area industrial vacuum coating in the 1990s Large-area vacuum coating is defined as vacuum processing of thin films and substrate surfaces which are significantly larger in area than integrated circuits. Historically, applications of large-area vacuum coating technology have included roll-to-roll metallized polymer films for capacitors, decorative packaging, and window glazing films; and coatings on rigid discrete substrates for decorative fixtures, precision mirrors and lenses, and antiglare CRT screens. New markets, evolving technologies, and societal concerns will influence the direction and growth of largearea industrial vacuum coating technology in the 1990s. With the increase of two-worker households and the corresponding popularity of convenience cooking, food packaging materials which provide extended shelf life and enhance microwave preparation will be a growing market. More demanding requirements for recording media, medical applications, and space technology will generate new commercial opportunities for largearea vacuum coating. And concerns relating to control of toxic byproducts of industrial coating, plating and etching processes will cast large-area vacuum processing in an attractive new light. P R Johansen, J Vac Sci Technol, A8, 1990, 2798-2801.
• ,,
21 7179. A comparison of SiO2 planarization layers by hollow cathode enhanced direct current reactive magnetron sputtering and radio frequency magnetron sputtering SiO2 films have been prepared by hollow cathode enhanced dc reactive magnetron sputtering [J J Cuomo and S M Rossnagel, J Vac Sci Technol, A4, 393 (1986)] and for comparison by rf magnetron sputtering from an SiO2 target. The hollow cathode arc source is used in a triode configuration with the magnetron. This configuration allows sputtering to take place at pressures as low as 5 x 10 4 tort, as well as sputtering of the oxide without arcing below ~ 600 V. These films were investigated as a dielectric planarization layer for Josephson (superconducting) devices. To this end, film deposition parameters (02 flow rate, Ar partial pressure, magnetron target voltage, hollow cathode current) have been related to film deposition rate, index of refraction, measured by ellipsometry, stoichiometry, measured by X-ray photoelectron spectroscopy (XPS), and coating conformity as measured by electron microscopy. A similar set of experiments was performed for the rf sputtered films. The relationships were investigated using factorial experiment design. D F Dawson-Elli et al, J Vac Sci Technol, A8, 1990, 1294-1298. 21 7180. Beam parameter effects on magnetic properties of sputtered amorphous Fe40Ni4oBisSis and Fe4oCo4oB15Si5 films Amorphous films were deposited onto fused quartz by ion beam sputter deposition to examine possible alternatives to existing polycrystalline microwave materials. Ion beam parameters were systematically varied to determine the dependence of film magnetic properties on beam conditions. Chemical composition of representative films were confirmed using Auger electron spectroscopy and Rutherford backscattering spectroscopy. Amorphousness was confirmed by X-ray diffraction analysis, and film thickness was determined by surface profilometer trace. Film magnetic properties were measured by vibrating sample magnetometer and ferromagnetic resonance techniques. It was found that films deposited under higher beam energies showed the lowest eoercivities and anisotropy fields. Saturation magnetization values remained largely unaffected by beam parameter variation. Evidence suggests vacuum base pressure plays a significant role in film magnetic properties. Improvement of the films' soft magnetic properties with increased beam energy may be attributed to reductions in trapped impurities resulting from increased deposition rates. The resulting films display promising properties for microwave magnetic applications. V G Harris et al, J Vac Sci Technol, A8, 1990, 1325 1329. 21 7181. Characterization of sputter-deposited ZrBxOy films ZrBxOy films for optical durable coating application were deposited by reactive dc magnetron sputtering of Zr-B alloy target on soda-lime silica glass substrate without intentional heating. Effect of boron content on film properties was investigated. The refractive index of the film was decreased from 2.1 to 1.69 corresponding to the increase of B203 content from 0 to 64 mol%. The films containing more than 13 mol% B20 3 fraction were amorphous and showed remarkably improved mechanical durability compared with ZrO2 film. More than 51 mol% B203 content resulted in degrading of chemical durability. Measurement of mechanical properties was carried out together with characterization on crystalline structure and chemical binding state. J Ebisawa et al, J Vac Sci Technol, A8, 1990, 1335 1339. 21 7182. Properties of W-N and Mo-N films prepared by reactive sputtering The structure and properties of W - N films up to 22 #m thick prepared by a reactive dc magnetron sputtering process are reported. It has been found that the properties of the deposited films not only depend on the nitrogen partial pressure in the argon-nitrogen gas mixtures but also on total gas pressure and input power during sputtering. The rate of deposition decreased with increase of nitrogen partial pressure, but was higher at higher total pressure and input power. The resistivity increased with nitrogen partial pressure but was lower at lower total gas pressure and higher input power. The hardness of W N films could be varied from 600 to 3000 kg mm 2 depending on sputtering conditions. The hardness, in general, increased with nitrogen partial pressure with higher value at higher total pressure and input power. X-ray diffraction did not indicate presence of nitride phases when the content of nitrogen in the argon nitrogen gas mixtures during sputtering was below 10%, and the total gas pressure was <40 mtorr. WzN was observed when the nitrogen 567
Classiqed abstracts 7183-7191
content was over 30% and also when the nitrogen content was over 10% and total gas pressure was over 40 mtorr. These results are consistent with composition determined by the microprobe measurements. Similar studies on Mo N films made by dc and rf magnetron reactive sputtering methods are reported. Hardness values for the Mo N films of more than 2200 kg m m 2 have been observed. K K Shih and D B Dove, J Vac Sci Technol, A8, 1990, 1359 1363. 21 7183. Low resistivity indium-tin oxide transparent conductive films. I. Effect of introducing H20 gas or H2 gas during direct current magnetron sputtering When an inline sputtering system is used to make conductive transparent ITO film by the direct current (de) magnctron sputtering method, it was found that the partial gas pressure of H 2 0 affected the properties of deposited films. When the substrate temperature is at or below 200< C, the control of H 2 0 partial gas pressure is especially important. Using room temperature substrates, an addition of 2 × I0 ~ torr of H 20 in the sputtering process could form ITO films with good repeatability at a low resistivity of 6.0 x l0 4 Q cm. By adding H 2 0 gas, it was possible to solve the issue of increased resistivity in thicker films. The films with added I t 2 0 gas have H element immersed into the film and have high carrier concentration. Film transmittance stayed constant with or without H 20 gas addition. A similar effect was observed by adding H_~ gas instead of H 2 0 gas. S Ishibashi et al, J Vac Sci Technol, A8, 1990, 1399 1402. 21 7184. Characterization of radio frequency deposited thin carbon films Thin carbon films (2(~50 nm) synthesized from an acetylene rf plasma were characterized by m i c r o - R a m a n spectroscopy, Rutherford backscattering spectroscopy (RBS), forward recoil spectroscopy (FRES), and laser-ablation/Fourier transform mass spectrometry (FTMS). The films were found to be free of any metal impurities by RBS and FTMS. FRES indicated low hydrogen content. Pronounced changes in the R a m a n spectra of films baked in nitrogen suggest structural transformations. The films underwent a transition from a m o r p h o u s to graphitic-like structures after a 24 h bake at 400<'C. Comparison of the R a m a n spectra of the rfdeposited films to those of control films formed from graphite indicated subtle structural differences. L M Siperko et al, J Vac Sci Technol, A8, 1990, 1533 1537. 21 7185. Simulation and measurement of density variation in Mo films sputter deposited over oxide steps A density profile for sputtered metal deposited over a step is generated using SIMulation by BAllistic Deposition (SlMnAD), a two-dimensiomd computer simulation of thin film growth by ballistic deposition of hard disks. By postdeposition etching of a real Mo film deposited over a similar step, regions with high etch rate are identified. As etch rate is relatcd to density, these are assumed to be low density sections, and arc in fact found to agree well with low density regions predicted by the simulations. R N Tait et al, J Vac Sci Technol, A8, 199(I, 1593 1596. 2I 7186. Dielectric properties of rf-sputtered YzO3 thin films Yttrium oxide (Y203) thin films were deposited on indium tin-oxide (lTO)-coaled glass substrates by the if-sputtering method using an Y ~O ~sintered target. The relative dielectric constant ~:~ and the dielectric strength E,t j of the Y20 3 films were studied. It was found that c, and EB, have a m a x i m u m value and a m i n i m u m value, respectively, at 1.3 Pa when the pressure of the sputtering gas, A r + 10% 02, is varied from 0.67 to 9.3 Pa. The X-ray diffraction study showed that the Y 2 0 3 films deposited at 1.3 Pa arc predominantly oriented along the (332) direction and their grain size is the smallest. Ion mass analysis showed impurity diffusion tYom ITO in the films deposited at 1.3 Pa. Furthermore, the dielectric properties of the Y20~ films deposited at 1.3 Pa are related to the structural properties, such as the (332) orientation, grain size, and impurity diffusion. K Onisawa et ai, J Appl Phys, 68, 1990, 719 723. 21 7187. rf diode sputtering A review of rf sputtering principles is presented with reference to recent plasma models and sample calculations. Typical modern sputtering equipment is described and methods of measurement of important pro568
cess variables. Application to the sputtering of Si()~ is described, with data on film properties as a function of bias, rate and oxygen additions. J S Logan, Thin Solid Films, 188, 1990, 307 321. 21 7188. High-rate sputter deposition of SiO2 and TiO~ films for optical applications This paper describes a process to produce SiO: and "l'iO2 films at high rates of deposition by using chemically reactive gases (etch gases). Experiments were conducted using CI> CCI4, CCI~F, CCIF 3, and H 2 mixed individually in Ar and O2 plasma in a magnetron sputtering process. Oxide films were deposited on glass and Si substrates from sputter-etching of St, SiO2, Ti,d and TiO, targets. An attempt was made to understand the mechanism involved in the increased rate of deposition. The results showed that considerable enhancement of the rate of deposition was obtained for SiO3 and TiO2 fihns when sputtered from their pure elemental targets. The enhancement in the rate of deposition ranged between 5 and 30 times over that obtained in a conventional reactive sputtering process. The analysis of the process during sputtering indicated that deposition was accompanied by the formation of volatile chlorides resulting from the chemical etching of the targets. In most cases the coatings had refractive indices close to those of the bulk SiO2 and TiO2, the films were clear and had good resistance to scratching. However, at high concentrations of the etch gases, the optical and scratch properties of the films deteriorated. S S Nandra, J Vac Sci 77,chnol, A8, 1990, 3179 3185. 21 7189. Evaluation of the stopping depth of nonradiative recombination centers in Al~.sGa..sAs by Ar ~ ion beam sputtering by photoluminescence measurements The stopping depth of nonradiativc recombination centers m AI, ~(ia,~ As by Ar + ion beam sputtering was evaluated by photoluminescence (PL) measurements using Al,~Ga0~As/GaAs single heterostructures. Al,~Ga0 ~As layers were sputtered by an Ar ~ ion beam with energies from 0.5 to 3 keV at temperatures l¥om 0 to 3 0 0 C . The PL intensity of the underlying G a A s was measured to detect the damage (nonradiative recombination center). The thickness of the residual AI~)~Ga0,As layer at which the PL intensity of the G a A s began to fall was taken as the stopping depth of nonradiative recombination centers. This depth increased as Ar ~ ion energy increased and sputtering temperature decreased. The depth of damage was roughly proportional to the A r ' ion energy E at about 25 (; for E less than 3 keV. K Akita et al, J Vac Sci Techmd, A8, 1990, 3274 3278. 21 7190. Surface-defect formation in graphite targets during magnetron sputtering Magnetron sputtering of graphite targets is frequently marred by the formation of topographic defects. The defects are either soft with a furry appearance or hard with a stalagmite appearance. The soft defects are often li)und on top of the hard ones, implying a close connection in Ibrmation sequence betwccn the two typcs of defects. The formation mechanism of thc hard defects is related to the presence on thc surface of low sputtering-yield impurities or other types of lattice imperfections, which suppress the erosion induced locally by sputtering, and to porosityinduced asperities. The emergence of the soft defects is ascribed to a growth p h e n o m e n o n involving rcdeposition of carbon from debris and possibly generated in a chemical vapor deposition (CVD) process. The gradual coverage of the target surface by defects causes a steady decrease of the sputtering rate of carbon. Also, the breakup of the soft defects promotes nodular defects in the subsequent growth of the carbon fihn, thus severely degrading the film quality. Remedial measures are devised for limiting the onset of defect formation. C W Chen et al, J Vac Sci Technol, A8, 1990, 3157 3162. 21 7191. Media noise in periodic multilayered magnetic films with perpendicular anisotropy Periodic, finely multilayered thin-film magnetic structures ( ~<200/~) with high in-plane coercivity suitable for longitudinal recording investigations have been fabricated. C o P t , . / P d and CoPt~ ,Cri 7/Pd periodic multilayers can exhibit a perpendicular orientation, originating from surface anisotropy effects, with a magnitude depending on the thickness of the component layers. The perpendicular orientation influences the transition noise, but for the particular systems studied, the results suggest that for