- Email: [email protected]
Ni films
Classified abstracts 7465-7472 ance of 40% for thicknesses of 15-20 nm. The influence of cosputtering conditions on the film composition is discussed. C Sella et al, Vacuum, 41, 1990, 117~1175. 21 7465. Magnetron sputtering deposited AIN waveguides: effect of the structure on optical properties A l u m i n i u m nitride thin films have been deposited on glass substrates by dc magnetron reactive sputtering in Ar + N2 mixtures. Films are studied by waveguide optical methods and a refined X-ray diffraction technique (phase analysis and pole figure analysis). At low pressure the refractive index is high and the films exhibit a strong fibre crystallographic orientation (002). The optical losses are high due to the roughness of the surface. At high pressure and high current, the films are similar to the low pressure ones but not so highly textured. At low current the index decreases and corresponds to a new growth direction. The c-axis tends to be parallel to the substrate plane. Optical losses become low. These behaviours are interpreted in terms of ion b o m b a r d m e n t of the growing film as evidenced by the influence of an rf substrate bias on film growth. A Cachard et al, Vacuum, 41, 1990, 1151 1153. 21
7466. The growth of sputter-deposited silver-copper films Silver-copper was chosen as an example of a simple eutectic system in which to observe the formation of a two phase eutectic structure in thin film form. Alloy films were deposited in an uhv dc magnetron sputter deposition system from separate targets of the two elements. Substrates were glass and carbon-coated grids for transmission electron microscopy. Composition and substrate temperature were varied and films of varying thickness were deposited in order to observe the evolution of film structure. X-ray diffraction line broadening and electron microscopy gave information on the early stages of film growth, crystallographic texture, non-uniform strain and grain size. A detailed analysis of X-ray diffraction traces using the theory of Witt and Vook [3' Appl Phys, 39, 2773 (1968)] on the change in the interplanar spacing normal to a film which is under a thermal strain has given the level o f thermally-induced strain within the films. Accurate lattice parameters show the extent of solid solubility of the two elements when deposited under different conditions. Z H Barber, Vacuum, 41, 1990, 1102-1105. 21
7467. Synchrotron radiation photoionization of sputtered neutrals A photoionization effect of sputtered neutrals by synchrotron radiation (SR) is observed for the first time. Synchrotron radiation from a bending magnet is irradiated 5 m m 'above' the Ar ion sputtered area of the sample surfaces, and photoionized ions and secondary ions are detected with a quadrupole mass spectrometer with and without this Sr irradiation. A large ratio o f photoionized ions to secondary ions is obtained when Au and Pb are sputtered with a low primary Ar ion energy. On the contrary, no detectable photoionization effect is observed from A1, Si, or GaAs. These results are explained qualitatively by the photoionization process where the n u m b e r of generated ions can be calculated based on the photon flux density, photoionization cross-sections, and duration in which sputtered neutrals pass through the SR beam. M Oshima et al, J Vac Sci Technol, A8, 1990, 257~2575. 21 7468. Effect of deposition parameters on properties of films deposited on
fibers by hollow cathode magnetron sputtering Thin films o f A1 and TiN were deposited on SiC monofilaments using a hollow cathode magnetron sputtering system. The deposition rate was 1 I00/~ min -~ in the case of A1 films deposited at 45.75 W direct current power and 5 m torr sputtering pressure and 257/~ min ' for TiN films deposited at 6 m torr sputtering pressure, 6% N2, and 48 W applied direct current power. The effects of deposition parameters such as the direct current power, sputtering pressure, and substrate bias on the film microstructure were studied. The substrate temperature varied from 67.7 to 168°C, which corresponds to a T/Tm value of 0.1-0.25. The A1 films consisted of a voided columnar structure with domed tops. The width of the grains increased with increase in temperature over a T/Tm range of 0.14).22. When the pressure was increased, while keeping the power constant, the size of the columnar grains and voids decreased. The TiN films deposited at 6 mtorr exhibited zone 1 type structure with voids whereas for the films deposited at higher pressures, that is, 10 and 15 mtorr, the same effect of pressure as in the case orAl films was seen. When a bias is applied to the substrate, the voided structure is clearly suppressed. 670
Preliminary studies show that bias sputtered films show better diffusion barrier properties against both Si and A1, after being annealed at 650°C for 6 h, as compared to the films deposited without bias. M lhsan and K Pourrezaei, J Vac Sci Technol, A8, 1990, 1304-1312. 21
7469. Process parameter-growth environment-film property relationships for the sputter deposited yttrimn--oxygen system In this study, a Y target was sputtered in radio frequency (rf)-excited, rare gas discharges (Ne, Ar) containing 0 4 0 % O2, operated at a cathode voltage from - 1.0 to 1.7 kV. In situ optical emission spectrometry was used to monitor two neutral excited Y atom transitions (2 = 0.6191, 0.6793 pm) and an excited O atom transition (2 = 0.7774 #m) as a function of changing process parameter. Films were grown on fused SiO2 substrates, and their crystallography, optical behavior, and electrical resistivity was determined. A 'phase diagram' for Y~O not grown under conditions of equilibrium thermodynamics was constructed, and included hexagonal Y, cubic Y203, and Y and Y203 that had no long range crystallographic order. Two direct optical transitions across the energy band gap of cubic Y203, at 5.07 and 5.73 eV, were identified. Combining discharge diagnostics, growth rate, and film property results, it was concluded that Y203 was formed at the substrate concurrent with the complete oxidation of the target surface. Even after target oxidation, the discharge contained atomic Y. On the basis of fundamental optical absorption edge characteristics, cubic Y203 that more closely resembled the bulk material was obtained when the Y-oxide molecule/Y atom flux to the substrate was high. Chee-Kin Kwok et al, J Vac Sci Technol, A8, 1990, 133(~1334. 21 7470. Mechanical properties of high deposition rate SiO2 films Thick overcoats of SiO2 sputtered at high deposition rates in a radiofrequency (rf) diode system are being considered as alternatives to A1203 and photoresist as passivation and planarization layers in the fabrication of thin film magnetic recording heads. The mechanical properties of 7# m thick SiO2 films sputtered onto silicon substrates were examined as functions of bias voltage and 02 gas flow. A high rate of 3.69 # m h J was achieved in a production system at substrate temperatures below 40°C. The addition of 02 decreased the deposition rate to 1.65 # m h-% The decrease in deposition rate produced an improvement in the p-etch rate, hardness and stress, but no change in the film density or morphology. The addition of a bias voltage during deposition was found to have the biggest effect on film properties. Bias sputtered films were found to be completely devoid of the columnar structure found in films deposited without bias. The addition of a small bias voltage reduced the film stress from - 16 x 108 dyn cm -2 to - 0 . 4 x 108 dyn cm -2. However, increasing the bias voltage further caused the film stress to increase to - 3 . 6 × l0 s dyn cm -2 at - 160 V bias. This effect can be correlated with the increased Ar content of the films. The p-etch rates of bias sputtered films dropped two orders of magnitude to 10 A. s -~. The K n o o p hardness increased from 423 without bias to 663 with bias and the film density increased slightly. C V Macchioni, J Vac Sci Technol, A8, 1990, 1340~1343. 21 7471. The effects of biasing and annealing on the optical properties of radio-
frequency sputtered VO2 Vanadium dioxide thin films were deposited by radio-frequency (rf) reactive sputtering. A n in situ anneal was found to improve stoichiometry, alter optical contrast, and increase grain size for a set of films. Biasing of a second set of substrates during deposition was found to increase the infrared (ir) transmission of films in the metallic state and degrade hysteresis characteristics. A Razavi et al, J Vac Sci Technol, A8, 1990, 1391 1394. 21 7472. Synthesis and structure of ion-beam sputtered multilayer Fe/Ni films Multilayers of Fe/Ni with equal thickness of Fe and Ni layers have been deposited on Si and glass substrates using ion-beam sputtering with composition modulation wavelength 2 ranging from 20 to 160 A. X-ray diffraction scans using Cu K s radiation were made to look for the satellite peaks that are the signature of coherent multilayers. Satellite peaks were observed only when argon ion-assisted deposition was used in preparing the multilayers. Read photographs using Fe K s radiation show that the films are highly textured. All the diffraction rings in the Read photograph can be identified to a single face-centered-cubic (fcc) lattice for 2 ~< 36 ~ . For higher wavelengths, rings corresponding to body-centered-cubic
Classified abstracts 7473-7479 (bcc) Fe were observed in the Read photographs. Extended X-ray absorption fine structure (EXAFS) measurements taken above the Fe K edge indicate that the Fe in the FejNi multilayers are in fcc and bcc phases for wavelengths of 27.6 and 120 A, respectively. The average lattice parameter shows an enhancement with decreasing wavelength that is proportional to 1/2 for 26.4 ~< 2 ~< 52.0/~. C Kim et al, J Vac Sci Technol, A8, 1990, 1407-1410. 21 7473. Modeling of inhomogeneous film deposition and target erosion in reactive sputtering Presented is a generalized microphysical model for reactive sputtering, taking into account inhomogeneities of both the target erosion and the deposition of films on condensing surfaces of substrates and chamber walls. The integral quantities, as the total metal ejection rate or the reactive gas consumption, can be treated as if the erosion and deposition were homogeneous but over properly determined effective areas. Conversely, the local quantities, as the target coverage by the compound or the film composition, are strongly influenced by the inhomogeneities. Both chamber wall area Awand the substrate area A~influence the system behavior. An increase of A, and/or decrease of A wleads to higher reactive gas content in films. This effect makes it possible to use a simple flow rate control for a high rate deposition of nearly stoichiometric films, as TiN, in the metallic mode of target operation. S Kadlec et al, J Vac Sci Technol, A8, 1990, 1560-1565. 21 7474. Effects of nitrogen pulsing on sputter-deposited beryllium films Beryllium films have been used as a 'heat sink' layer between the reflective coating of a mirror and its glass substrate to improve the mirror's radiation resistance to prompt deposition of X-rays. Under X-ray irradiation, the beryllium heat sink layer is subjected to tensile stresses caused by differences in thermal expansion coefficients. Test results indicated that the predominant failure mode was the film's crazing under tensile stress. The inherent columnar structure of the beryllium films deposited under normal conditions is detrimental to the tensile strength of the films and may be responsible for this type of failure. We successfully suppressed the inherent columnar growth in beryllium films by incorporating periodic N2 pulses during sputter deposition. The traditional substrate biasing approach did not seem to be as effective in modifying the grain structure. The results showed that higher N2 pulse rates during deposition were more effective in suppressing the columnar growth. However, we noticed that films deposited with nitrogen pulsing show higher secondary-electron emission in SEM micrographs, which indicates a significant incorporation of contaminants into the beryllium films. Quantitative analyses were conducted for nitrogen and oxygen contamination in the beryllium films using standards prepared by ion implantation. Secondary ion mass spectroscopy (SIMS) depth profiles were obtained for oxygen and nitrogen using mass isotopes ~60 and 23(gBe+~4N). More than 2% of contaminants were observed in beryllium films at the higher pulse rates that were used. Thus, a minimum pulsing frequency and duration should be selected that provides grain refinement with a minimum amount of contamination. E J Hsieh et al, J Vac Sci Technol, A8, 1990, 2165-2168. 21 7475. Optimizing optical properties of reactively sputtered titanium nitride films New results on the optical properties of titanium nitride films are reported. Opaque and semitransmitting TiN films were prepared by dc sputtering from a titanium target in an A~N2 atmosphere. The sputtering system was deliberately overpumped to avoid hysteresis effects from target poisoning. It is demonstrated in detail that substrate heating during deposition significantly increases the ir reflectance and reduces the reflectance minimum in the visible region for opaque films. The heat mirror performance of semitransmitting, 10-20 nm thick films on glass is similarly improved. The improvement is attributed to reduction in lattice strain and oxygen and carbon impurity content as observed by X-ray diffraction and Auger electron spectroscopy. The results indicate that slightly overstoichiometric films exhibit better optical performance. A Skerlavaj et al, Thin Solid Films, 186, 1990, 15-26 21 7476. Stress state of chromium nitrid ; films deposited by reactive direct current planar magnetron sputtering Chromium nitride films were deposited on glass substrates using reactive
dc planar magnetron sputtering. Film stress-state evaluation permitted a two-level classification into compressive and transition categories. Maximum stress levels in these compressive category films were in the ( - ) 0.83 to ( - ) 14.4 GPa range. Sputtering parameter weighting equations indicated the deposition parameters which influenced stress were sputtering pressure, sputtered flux incidence angle, film thickness, and the interactions between these parameters. Subsequent studies indicated substrate bias to be important in the - 5 0 to - 2 5 0 V interval. Thermal stresses contributed a compressive component of ( - ) 0.7 GPa which was approximately 4% of the peak compressive stress. Generally, deposition conditions promoting high normalized energies (energetic particle bombardment of the film) produced hard coatings which were highly stressed (compressive) with low resistivities. P M Fabis et al, J Vac Sci Technol, A8, 1990, 380~3818. 21 7477. Preparation and electrical properties of n-Ti2N thin films An e-Ti2N film nearly free from any other phase of the T i N compound was deposited and the temperature dependencies of the resistivity and the Hall coefficient of the film were measured. The resistivity data were analyzed in terms of the Bloch~3riineisen equation. The characteristic temperature 0 of the film was 410.8 K, independent of the temperature ranging from 4.2 to 300 K. From a Hall measurement it was determined that the conduction carriers in the e-Ti2N were holelike over the temperature range from 77 to 300 K. Y Igasaki and H Mitsuhashi, J Appl Phys, 68, 1990, 2439-2441. 21 7478. Sputtering of excited-state potassium atoms from electron-bombarded KBr crystals Sputtering of excited-state potassium atoms from electron-bombarded KBr crystals has been investigated at 300 and 443 K by measuring simultaneously the optical emission, Auger, and mass spectra. The beam current dependences of the intensities of the ground-state and excitedstate potassium atoms at 443 K are nearly linear and quadratic, respectively, indicating that excited-state potassium atoms are produced by gas-phase collisions of potassium atoms desorbed from the surface. On the other hand, the room-temperature data show complicated dependences, which can be divided into three current regions. In the lowcurrent region (<13 #A), electronic excitation followed by Augerinduced Coulomb repulsion produces the excited-state potassium atoms. In the high-current region (> 25 #A), effects due to sample decomposition, nonstoichiometry, and gas-phase collisions play important roles in the production of excited-state potassium atoms. The nonlinear sputtering yield of excited-state potassium atoms in the intermediate-current region may be due to secondary effects including the formation of defects and cluster ions. M Kamafla and E T Arakawa, J Vac Sci Technol, A8, 1990, 3152-3156. 21 7479. Fabrication and chemical composition of rf magnetron sputtered TICa-Ba-Cu-O high Tc superconducting thin films High-temperature superconducting T I ~ C ~ B a ~ C u ~ (T1CaBaCuO) thin films were fabricated by rf magnetron sputtering on strontium titanate (SrTiO3) substrates. Thin films of 0.5~).7-#m thickness were deposited by pure argon sputtering from a single composite powder target of T12Ca2Ba2Cu3Ox at an rf power of 250 W and a pressure of 5 mtorr. Asdeposited thin films were sintered and annealed in a thallium-rich ambient to obtain superconductivity with a zero resistance temperature (To0) at 107 K. X-ray diffraction results showed highly c-axis oriened films with T12Ca2Ba2Cu3Ox (2223) and Tl:Ca~Ba2Cu2Ox (2122) phases present. Auger electron spectroscopy survey and depth profiles were performed to determine the compositional uniformity and impurity contents of the thin films. X-ray photoelectron spectroscopy high-resolution spectra were obtained at the surface, in the bulk, and near the interface with the substrate. Our XPS results support two possible mechanisms for the creation of holes in the T1CaBaCuO compound: (1) partial substitution of Ca 2+ for T13+ and (2) charge transfer from T13+ to the CuO layers resulting in a valence of T1 between + 3 and + 1 states and the creation of holes in the CuO layers. In addition, a wet chemical etching process was developed for patterning the as-deposited T1CaBaCuO thin films. A 125-/tm-wide line was formed using standard photolithography and wet chemical etching which, after heat treatments, showed superconductivity with a T,.0 of 80 K. G Sabramanyam et al, J Appl Phys, 68, 1990, 1157 1163.
671
7466. The growth of sputter-deposited silver-copper films Silver-copper was chosen as an example of a simple eutectic system in which to observe the formation of a two phase eutectic structure in thin film form. Alloy films were deposited in an uhv dc magnetron sputter deposition system from separate targets of the two elements. Substrates were glass and carbon-coated grids for transmission electron microscopy. Composition and substrate temperature were varied and films of varying thickness were deposited in order to observe the evolution of film structure. X-ray diffraction line broadening and electron microscopy gave information on the early stages of film growth, crystallographic texture, non-uniform strain and grain size. A detailed analysis of X-ray diffraction traces using the theory of Witt and Vook [3' Appl Phys, 39, 2773 (1968)] on the change in the interplanar spacing normal to a film which is under a thermal strain has given the level o f thermally-induced strain within the films. Accurate lattice parameters show the extent of solid solubility of the two elements when deposited under different conditions. Z H Barber, Vacuum, 41, 1990, 1102-1105. 21
7467. Synchrotron radiation photoionization of sputtered neutrals A photoionization effect of sputtered neutrals by synchrotron radiation (SR) is observed for the first time. Synchrotron radiation from a bending magnet is irradiated 5 m m 'above' the Ar ion sputtered area of the sample surfaces, and photoionized ions and secondary ions are detected with a quadrupole mass spectrometer with and without this Sr irradiation. A large ratio o f photoionized ions to secondary ions is obtained when Au and Pb are sputtered with a low primary Ar ion energy. On the contrary, no detectable photoionization effect is observed from A1, Si, or GaAs. These results are explained qualitatively by the photoionization process where the n u m b e r of generated ions can be calculated based on the photon flux density, photoionization cross-sections, and duration in which sputtered neutrals pass through the SR beam. M Oshima et al, J Vac Sci Technol, A8, 1990, 257~2575. 21 7468. Effect of deposition parameters on properties of films deposited on
fibers by hollow cathode magnetron sputtering Thin films o f A1 and TiN were deposited on SiC monofilaments using a hollow cathode magnetron sputtering system. The deposition rate was 1 I00/~ min -~ in the case of A1 films deposited at 45.75 W direct current power and 5 m torr sputtering pressure and 257/~ min ' for TiN films deposited at 6 m torr sputtering pressure, 6% N2, and 48 W applied direct current power. The effects of deposition parameters such as the direct current power, sputtering pressure, and substrate bias on the film microstructure were studied. The substrate temperature varied from 67.7 to 168°C, which corresponds to a T/Tm value of 0.1-0.25. The A1 films consisted of a voided columnar structure with domed tops. The width of the grains increased with increase in temperature over a T/Tm range of 0.14).22. When the pressure was increased, while keeping the power constant, the size of the columnar grains and voids decreased. The TiN films deposited at 6 mtorr exhibited zone 1 type structure with voids whereas for the films deposited at higher pressures, that is, 10 and 15 mtorr, the same effect of pressure as in the case orAl films was seen. When a bias is applied to the substrate, the voided structure is clearly suppressed. 670
Preliminary studies show that bias sputtered films show better diffusion barrier properties against both Si and A1, after being annealed at 650°C for 6 h, as compared to the films deposited without bias. M lhsan and K Pourrezaei, J Vac Sci Technol, A8, 1990, 1304-1312. 21
7469. Process parameter-growth environment-film property relationships for the sputter deposited yttrimn--oxygen system In this study, a Y target was sputtered in radio frequency (rf)-excited, rare gas discharges (Ne, Ar) containing 0 4 0 % O2, operated at a cathode voltage from - 1.0 to 1.7 kV. In situ optical emission spectrometry was used to monitor two neutral excited Y atom transitions (2 = 0.6191, 0.6793 pm) and an excited O atom transition (2 = 0.7774 #m) as a function of changing process parameter. Films were grown on fused SiO2 substrates, and their crystallography, optical behavior, and electrical resistivity was determined. A 'phase diagram' for Y~O not grown under conditions of equilibrium thermodynamics was constructed, and included hexagonal Y, cubic Y203, and Y and Y203 that had no long range crystallographic order. Two direct optical transitions across the energy band gap of cubic Y203, at 5.07 and 5.73 eV, were identified. Combining discharge diagnostics, growth rate, and film property results, it was concluded that Y203 was formed at the substrate concurrent with the complete oxidation of the target surface. Even after target oxidation, the discharge contained atomic Y. On the basis of fundamental optical absorption edge characteristics, cubic Y203 that more closely resembled the bulk material was obtained when the Y-oxide molecule/Y atom flux to the substrate was high. Chee-Kin Kwok et al, J Vac Sci Technol, A8, 1990, 133(~1334. 21 7470. Mechanical properties of high deposition rate SiO2 films Thick overcoats of SiO2 sputtered at high deposition rates in a radiofrequency (rf) diode system are being considered as alternatives to A1203 and photoresist as passivation and planarization layers in the fabrication of thin film magnetic recording heads. The mechanical properties of 7# m thick SiO2 films sputtered onto silicon substrates were examined as functions of bias voltage and 02 gas flow. A high rate of 3.69 # m h J was achieved in a production system at substrate temperatures below 40°C. The addition of 02 decreased the deposition rate to 1.65 # m h-% The decrease in deposition rate produced an improvement in the p-etch rate, hardness and stress, but no change in the film density or morphology. The addition of a bias voltage during deposition was found to have the biggest effect on film properties. Bias sputtered films were found to be completely devoid of the columnar structure found in films deposited without bias. The addition of a small bias voltage reduced the film stress from - 16 x 108 dyn cm -2 to - 0 . 4 x 108 dyn cm -2. However, increasing the bias voltage further caused the film stress to increase to - 3 . 6 × l0 s dyn cm -2 at - 160 V bias. This effect can be correlated with the increased Ar content of the films. The p-etch rates of bias sputtered films dropped two orders of magnitude to 10 A. s -~. The K n o o p hardness increased from 423 without bias to 663 with bias and the film density increased slightly. C V Macchioni, J Vac Sci Technol, A8, 1990, 1340~1343. 21 7471. The effects of biasing and annealing on the optical properties of radio-
frequency sputtered VO2 Vanadium dioxide thin films were deposited by radio-frequency (rf) reactive sputtering. A n in situ anneal was found to improve stoichiometry, alter optical contrast, and increase grain size for a set of films. Biasing of a second set of substrates during deposition was found to increase the infrared (ir) transmission of films in the metallic state and degrade hysteresis characteristics. A Razavi et al, J Vac Sci Technol, A8, 1990, 1391 1394. 21 7472. Synthesis and structure of ion-beam sputtered multilayer Fe/Ni films Multilayers of Fe/Ni with equal thickness of Fe and Ni layers have been deposited on Si and glass substrates using ion-beam sputtering with composition modulation wavelength 2 ranging from 20 to 160 A. X-ray diffraction scans using Cu K s radiation were made to look for the satellite peaks that are the signature of coherent multilayers. Satellite peaks were observed only when argon ion-assisted deposition was used in preparing the multilayers. Read photographs using Fe K s radiation show that the films are highly textured. All the diffraction rings in the Read photograph can be identified to a single face-centered-cubic (fcc) lattice for 2 ~< 36 ~ . For higher wavelengths, rings corresponding to body-centered-cubic
Classified abstracts 7473-7479 (bcc) Fe were observed in the Read photographs. Extended X-ray absorption fine structure (EXAFS) measurements taken above the Fe K edge indicate that the Fe in the FejNi multilayers are in fcc and bcc phases for wavelengths of 27.6 and 120 A, respectively. The average lattice parameter shows an enhancement with decreasing wavelength that is proportional to 1/2 for 26.4 ~< 2 ~< 52.0/~. C Kim et al, J Vac Sci Technol, A8, 1990, 1407-1410. 21 7473. Modeling of inhomogeneous film deposition and target erosion in reactive sputtering Presented is a generalized microphysical model for reactive sputtering, taking into account inhomogeneities of both the target erosion and the deposition of films on condensing surfaces of substrates and chamber walls. The integral quantities, as the total metal ejection rate or the reactive gas consumption, can be treated as if the erosion and deposition were homogeneous but over properly determined effective areas. Conversely, the local quantities, as the target coverage by the compound or the film composition, are strongly influenced by the inhomogeneities. Both chamber wall area Awand the substrate area A~influence the system behavior. An increase of A, and/or decrease of A wleads to higher reactive gas content in films. This effect makes it possible to use a simple flow rate control for a high rate deposition of nearly stoichiometric films, as TiN, in the metallic mode of target operation. S Kadlec et al, J Vac Sci Technol, A8, 1990, 1560-1565. 21 7474. Effects of nitrogen pulsing on sputter-deposited beryllium films Beryllium films have been used as a 'heat sink' layer between the reflective coating of a mirror and its glass substrate to improve the mirror's radiation resistance to prompt deposition of X-rays. Under X-ray irradiation, the beryllium heat sink layer is subjected to tensile stresses caused by differences in thermal expansion coefficients. Test results indicated that the predominant failure mode was the film's crazing under tensile stress. The inherent columnar structure of the beryllium films deposited under normal conditions is detrimental to the tensile strength of the films and may be responsible for this type of failure. We successfully suppressed the inherent columnar growth in beryllium films by incorporating periodic N2 pulses during sputter deposition. The traditional substrate biasing approach did not seem to be as effective in modifying the grain structure. The results showed that higher N2 pulse rates during deposition were more effective in suppressing the columnar growth. However, we noticed that films deposited with nitrogen pulsing show higher secondary-electron emission in SEM micrographs, which indicates a significant incorporation of contaminants into the beryllium films. Quantitative analyses were conducted for nitrogen and oxygen contamination in the beryllium films using standards prepared by ion implantation. Secondary ion mass spectroscopy (SIMS) depth profiles were obtained for oxygen and nitrogen using mass isotopes ~60 and 23(gBe+~4N). More than 2% of contaminants were observed in beryllium films at the higher pulse rates that were used. Thus, a minimum pulsing frequency and duration should be selected that provides grain refinement with a minimum amount of contamination. E J Hsieh et al, J Vac Sci Technol, A8, 1990, 2165-2168. 21 7475. Optimizing optical properties of reactively sputtered titanium nitride films New results on the optical properties of titanium nitride films are reported. Opaque and semitransmitting TiN films were prepared by dc sputtering from a titanium target in an A~N2 atmosphere. The sputtering system was deliberately overpumped to avoid hysteresis effects from target poisoning. It is demonstrated in detail that substrate heating during deposition significantly increases the ir reflectance and reduces the reflectance minimum in the visible region for opaque films. The heat mirror performance of semitransmitting, 10-20 nm thick films on glass is similarly improved. The improvement is attributed to reduction in lattice strain and oxygen and carbon impurity content as observed by X-ray diffraction and Auger electron spectroscopy. The results indicate that slightly overstoichiometric films exhibit better optical performance. A Skerlavaj et al, Thin Solid Films, 186, 1990, 15-26 21 7476. Stress state of chromium nitrid ; films deposited by reactive direct current planar magnetron sputtering Chromium nitride films were deposited on glass substrates using reactive
dc planar magnetron sputtering. Film stress-state evaluation permitted a two-level classification into compressive and transition categories. Maximum stress levels in these compressive category films were in the ( - ) 0.83 to ( - ) 14.4 GPa range. Sputtering parameter weighting equations indicated the deposition parameters which influenced stress were sputtering pressure, sputtered flux incidence angle, film thickness, and the interactions between these parameters. Subsequent studies indicated substrate bias to be important in the - 5 0 to - 2 5 0 V interval. Thermal stresses contributed a compressive component of ( - ) 0.7 GPa which was approximately 4% of the peak compressive stress. Generally, deposition conditions promoting high normalized energies (energetic particle bombardment of the film) produced hard coatings which were highly stressed (compressive) with low resistivities. P M Fabis et al, J Vac Sci Technol, A8, 1990, 380~3818. 21 7477. Preparation and electrical properties of n-Ti2N thin films An e-Ti2N film nearly free from any other phase of the T i N compound was deposited and the temperature dependencies of the resistivity and the Hall coefficient of the film were measured. The resistivity data were analyzed in terms of the Bloch~3riineisen equation. The characteristic temperature 0 of the film was 410.8 K, independent of the temperature ranging from 4.2 to 300 K. From a Hall measurement it was determined that the conduction carriers in the e-Ti2N were holelike over the temperature range from 77 to 300 K. Y Igasaki and H Mitsuhashi, J Appl Phys, 68, 1990, 2439-2441. 21 7478. Sputtering of excited-state potassium atoms from electron-bombarded KBr crystals Sputtering of excited-state potassium atoms from electron-bombarded KBr crystals has been investigated at 300 and 443 K by measuring simultaneously the optical emission, Auger, and mass spectra. The beam current dependences of the intensities of the ground-state and excitedstate potassium atoms at 443 K are nearly linear and quadratic, respectively, indicating that excited-state potassium atoms are produced by gas-phase collisions of potassium atoms desorbed from the surface. On the other hand, the room-temperature data show complicated dependences, which can be divided into three current regions. In the lowcurrent region (<13 #A), electronic excitation followed by Augerinduced Coulomb repulsion produces the excited-state potassium atoms. In the high-current region (> 25 #A), effects due to sample decomposition, nonstoichiometry, and gas-phase collisions play important roles in the production of excited-state potassium atoms. The nonlinear sputtering yield of excited-state potassium atoms in the intermediate-current region may be due to secondary effects including the formation of defects and cluster ions. M Kamafla and E T Arakawa, J Vac Sci Technol, A8, 1990, 3152-3156. 21 7479. Fabrication and chemical composition of rf magnetron sputtered TICa-Ba-Cu-O high Tc superconducting thin films High-temperature superconducting T I ~ C ~ B a ~ C u ~ (T1CaBaCuO) thin films were fabricated by rf magnetron sputtering on strontium titanate (SrTiO3) substrates. Thin films of 0.5~).7-#m thickness were deposited by pure argon sputtering from a single composite powder target of T12Ca2Ba2Cu3Ox at an rf power of 250 W and a pressure of 5 mtorr. Asdeposited thin films were sintered and annealed in a thallium-rich ambient to obtain superconductivity with a zero resistance temperature (To0) at 107 K. X-ray diffraction results showed highly c-axis oriened films with T12Ca2Ba2Cu3Ox (2223) and Tl:Ca~Ba2Cu2Ox (2122) phases present. Auger electron spectroscopy survey and depth profiles were performed to determine the compositional uniformity and impurity contents of the thin films. X-ray photoelectron spectroscopy high-resolution spectra were obtained at the surface, in the bulk, and near the interface with the substrate. Our XPS results support two possible mechanisms for the creation of holes in the T1CaBaCuO compound: (1) partial substitution of Ca 2+ for T13+ and (2) charge transfer from T13+ to the CuO layers resulting in a valence of T1 between + 3 and + 1 states and the creation of holes in the CuO layers. In addition, a wet chemical etching process was developed for patterning the as-deposited T1CaBaCuO thin films. A 125-/tm-wide line was formed using standard photolithography and wet chemical etching which, after heat treatments, showed superconductivity with a T,.0 of 80 K. G Sabramanyam et al, J Appl Phys, 68, 1990, 1157 1163.
671