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7473. Modeling of inhomogeneous film deposition and target erosion in reactive sputtering
Classified abstracts 7473-7479 @cc) 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 Fe Ni multilayers are in fee and bee phases for wavelengths of27.6 and 120 d , respectively. The average lattice parameter shows an enhancement with decreasing wavelength that is proportional to l/3, for 26.4 < 3, d 52.0 A. C Kim et al, J Vuc Sci Technol, A8, 1990, 1407-1410. 21 7473. Modeling of inbomogeneous fihn 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 A, and the substrate area A, influence the system behavior. An increase of A, and/or decrease of A, leads 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 Vat Sci Tech&, AS, 1990, 156&1565.
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 N, 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 N, 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 I60 and 23eBe+14N). 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 Vat Sci Technol, AS, 1990,2 165-2 168.
7475. Optimizing optical properties of reactively sputtered titanium nitride fihns 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 Ar-N, 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, l(t20 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 current planar magnetron sputtering Chromium nitride films were deposited
: films deposited by reactive direct 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 -50 to -250 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 Vat Sci Technol, AS, 1990,3809-3818. 21 7477. Preparation and electrical properties of &-Ti,N thin films An c-T&N film nearly free from any other phase of the Ti-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-Griineisen equation. The characteristic temperature B 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 &-T&N 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 PA), electronic excitation followed by Augerinduced Coulomb repulsion produces the excited-state potassium atoms. In the high-current region (> 25 PA). 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 Kamada and E T Arakawa, J Vat Sci Technol, A8, 1990, 3 152-3 156. “1
7479. Fabrication and chemical composition of rf magnetron sputtered T’; Ca-Ba-Cu-0 high T, superconduc&g thin films _ High-temnerature sunerconducting TlCa-BaCua (TlCaBaCuOj thin films were fabricated by rf magnetron sputtering on itrontium tit&ate (SrTiO,) substrates. Thin films of 0.54.7-pm thickness were deposited by pure argon sputtering from a single composite powder target of Tl,Ca,Ba,Cu,O, 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 (T,,) at 107 K. X-ray diffraction results showed highly c-axis oriened films with Tl,Ca,Ba,Cu,O, (2223) and Tl,Ca,Ba,Cu,O, (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 TlCaBaCuO compound: (1) partial substitution of Ca’+ for T13+ and (2) charge transfer from Tl’+ to the CuO layers resulting in a valence of Tl 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 TlCaBaCuO thin films. A 125~pm-wide line was formed using standard photolithography and wet chemical etching which, after heat treatments, showed superconductivity with a T,, of 80 K. G Subramanyam et al, J Appl Phys, 68, 1990, 1157-I 163. 671
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 N, 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 N, 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 I60 and 23eBe+14N). 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 Vat Sci Technol, AS, 1990,2 165-2 168.
7475. Optimizing optical properties of reactively sputtered titanium nitride fihns 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 Ar-N, 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, l(t20 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 current planar magnetron sputtering Chromium nitride films were deposited
: films deposited by reactive direct 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 -50 to -250 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 Vat Sci Technol, AS, 1990,3809-3818. 21 7477. Preparation and electrical properties of &-Ti,N thin films An c-T&N film nearly free from any other phase of the Ti-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-Griineisen equation. The characteristic temperature B 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 &-T&N 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 PA), electronic excitation followed by Augerinduced Coulomb repulsion produces the excited-state potassium atoms. In the high-current region (> 25 PA). 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 Kamada and E T Arakawa, J Vat Sci Technol, A8, 1990, 3 152-3 156. “1
7479. Fabrication and chemical composition of rf magnetron sputtered T’; Ca-Ba-Cu-0 high T, superconduc&g thin films _ High-temnerature sunerconducting TlCa-BaCua (TlCaBaCuOj thin films were fabricated by rf magnetron sputtering on itrontium tit&ate (SrTiO,) substrates. Thin films of 0.54.7-pm thickness were deposited by pure argon sputtering from a single composite powder target of Tl,Ca,Ba,Cu,O, 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 (T,,) at 107 K. X-ray diffraction results showed highly c-axis oriened films with Tl,Ca,Ba,Cu,O, (2223) and Tl,Ca,Ba,Cu,O, (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 TlCaBaCuO compound: (1) partial substitution of Ca’+ for T13+ and (2) charge transfer from Tl’+ to the CuO layers resulting in a valence of Tl 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 TlCaBaCuO thin films. A 125~pm-wide line was formed using standard photolithography and wet chemical etching which, after heat treatments, showed superconductivity with a T,, of 80 K. G Subramanyam et al, J Appl Phys, 68, 1990, 1157-I 163. 671