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Sodium diffusion in plasma-deposited amorphous oxygen-doped silicon nitride (a-SiON: H films)
Classified abstracts 6 5 5 7 4 5 6 5 upper values ( ~ I m A cm 2) the columnar structure is not seen and only phase TiN is detected. These different results m a y be explained by the role of the discharge current and the control of ion b o m b a r d m e n t of the substrate during the film growth process. A Rousseau and J Guille, Vacuum, 38, 1988, 4 4 3 4 4 8 . 23 6557. Optical properties of spray-deposited tin oxide films Optical properties of spray-deposited tin oxide (TO) films are studied here. Optical grade TO films were deposited using monobutyl tin chloride and dibutyl tin diacetate solutions. The refractive index and extinction coefficient, n(2) and k(2), respectively, and film thickness of TO films are evaluated from spectrophotometric transmittance characteristics examined in the visible and UV regions. Since the interference effects are suppressed by the optical absorption in the near-IR region, both reflectance and transmittance spectra are used to evaluate n(2) and k(2) values. Spray-deposited TO films are found to be an indirect band gap material exhibiting an absorption m i n i m u m at ~ 1.0 /zm (k ~< 10-3), an energy gap at ~ 3.7 eV. A transition from a bounded electron model to a free electron model occurs at 2 -- 1.4/~m. Hulva Demiryont et al, Appl Optics, 26, 1987, 3803-3810. 23 6558. Ion-assisted deposition of lanthanum fluoride thin films Ion-assisted deposition has been used to deposit l a n t h a n u m fluoride thin films with near-unity film packing densities and no significant increase in absorption. Rutherford backscattering analysis has determined the effect of ion b o m b a r d m e n t on the film stoichiometries including the degree of fluorine deficiency. Oxygen atoms or c o m p o u n d s appear to occupy most of the available anion vacancies if sufficient oxygen is available in the ion beam or the residual atmosphere. James D Targove et al, Appl Optics, 26, 1987, 3733 3737. 23 6559. Recent trends in L P C V D and P E C V D New developments in low pressure (LPCVD) and plasma enhanced (PECVD) chemical vapor deposition are aimed at satisfying the materials and fabrication requirements imposed by the small geometries and complex topographies of VLSI circuits. Using a typical state-of-the-art C M O S structure as a flame of reference, recent trends in L P C V D and P E C V D process and equipment developments are reviewed. B Gorowitz et al, Solid State Technol, 30, 1987, 97-103. 23 6560. Plasma deposition of SiO2 gate insulators for a-Si thin-film transistors The principles governing the plasma deposition of SiO2 films for use as gate insulators in a-Si thin-film transistors (TFT's) are discussed. A deposition arrangement is described which favors the reaction at the substrate over that in the discharge volume. It is shown that the variables leading to large values of the breakdown field Ebk and to greatest stability of the flat band voltage V~ are the substrate temperature T~, the gas flow ratio N20/SiH4, and the ratio of the discharge half-period to the transit time of the ions between the electrodes, a-Si/SiO2 T F T ' s operated in the dc mode and in a mode simulating LC display operation show m u c h less shift of the threshold voltage Vth than do a-Si/Si3N4 T F T ' s for equivalent gate fields. J Dresner, J Vac Sci Technol, B6, 1988, 5 1 2 5 2 3 . 23 6561. Sodium diffusion in plasma-deposited amorphous oxygen-doped silicon nitride (a-SiON : H films) The dependence of22Na diffusivity in a-SiN : H fihns on hydrogen content, N/Si ratio, oxygen content, and temperature was determined. Measurements were made at 350, 375, and 400°C. The diffusion profiles for sodium in a-SiN : H films have two regions; a short Gaussian region and shallow linear region. We have interpreted these results using a structural model which describes the film as a two-phase mixture of a highly ordered Si3N4like phase and a highly disordered phase. Using this model we argue that the Gaussian region of the diffusion profile is due to "bulk" diffusion through the Si3N4-1ike phase and the shallow linear region is due to "fast" diffusion through the interracial region. At 400°C the "fast" diffusivity is on the order of 103 times larger than the "bulk" diffusivity. Howeve r, at 80°C the "fast" diffusion is approximately 105 times smaller than the bulk diffusivity. This large change in the ratio of the diffusion coefficients is due to the large difference in activation energy for the two mechanisms. 502
For "bulk" diffusion it is approximately 1.8 eV, whereas it is approximately 2.6 eV for "fast" diffusion. The high activation energy for "fast" diffusion is due to an interaction (association) o f the diffusing Na + ion with a ( N - S i - N ) group to form a N a - N - S i - N complex. The association energy for this complex is approximately 1.2 eV. We have observed only one region in the diffusion profiles in the oxygen-doped films. This region is due to "bulk" diffusion. The magnitude and activation energy for diffusion is strongly dependent upon the oxygen content. It decreases from approximately 1.8 to 1.3 eV when the oxygen content o f the film increases from 0% to 25%. These results are then used to discuss possible device reliability problems which m a y occur in oxygen-doped films. J W Osenbach and S S Voris, Jappl Phys, 63, 1988, 4494~4500. 23 6562. Ion-beam-induced desorption of Ar + ion clusters The mass distribution o f Ar + ion clusters desorbed from Ar solid at 20 K was measured for 1 ~< n ~< 38. The desorption was induced by bombardment of the solid by three different primary ions, Ne +, Ar +, and Kr +, at 6 keV. The mass distribution is not influenced greatly by the bombarding species. This agrees with the description of the experimental data by Rice, Ramsperger, Kassel, and Marcus ( R R K M ) theory incorporating the charge-transfer process. Certain "magic n u m b e r " cluster ions were also observed in the Ar + mass distribution. J W Christiansen et al, J Vac Sci Technol, A6, 1988, 699-702. 23 6563. Contamination effects in glow discharge deposition systems The slow release of reactive gases from the walls and electrodes of practical plasma enhanced chemical vapor deposition (PECVD) systems has been studied. These desorption effects become important when thin films with different compositions are sequentially deposited in single-chamber deposition systems. The pressure rate of rise o f a P E C V D reactor was measured after exposure of the system to commonly used precursor gases. The nature of the gas, its pressure, the system temperature, and the time duration of the exposure are experimental variables. Contamination effects by dopants at the parts per million level were investigated by their effect on the electrical properties of subsequently deposited films. It is found that a m m o n i a and diborane, both of which are extensively used for device fabrication, are especially difficult to remove from the system. Operational procedures such as long p u m p o u t times, baking, and short exposure times to the gases, preferably at low pressures, can often reduce the extent of the carryover to an acceptable level in a single-chamber system. However, the use of multichamber systems is likely to be the most effective solution to crosscontamination problems in P E C V D processes. Frank Jansen and Dan Kuhman, J Vac Sci Technol, A6, 1988, 13 18. 23 6564. Mechanical property and structure relationships in hard coatings for cutting tools The trends in the use of hard protective coatings in W C Co metal cutting inserts are reviewed in light of recent evaluations of mechanical and structure-sensitive properties such as elevated temperature microhardness, microfracture toughness, and internal stress. A better understanding of the role of hard coatings has evolved due to development of reliable methods to measure mechanical properties of thin coatings (of the order of 5/z thick). There are intrinsic differences in the microstructure and residual stress state of chemical and physical vapor deposited (CVD and PVD) hard coatings. High compressive residual stress and fine grain size in PVD coatings contribute to increased microhardness and microfracture toughness. However, these benefits are reduced at high temperatures. Certain well-known structure/property concepts in bulk materials are shown to be applicable to hard coatings, which aid in interpretations of metal cutting wear behavior. Dennis T Qninto, J Vac Sci Technol, A6, 1988, 214~2157. 23 6565. On the existence of point defects in physical vapor deposited films of TiN, ZrN, and HfN Sets of experimental data from a n u m b e r of different techniques are summarized in the present work. They indicate that lattice defects in the form of vacancies and interstitials are very often present in films of the group-IVB nitrides as prepared by plasma enhanced physical vapor deposition methods. Lattice parameters, even allowing for the presence of residual stresses, density and positron annihilation data and the effect of deposition conditions on the reflectance and color of films, together with the effects of tempering, indicate that the fraction of interstitials
For "bulk" diffusion it is approximately 1.8 eV, whereas it is approximately 2.6 eV for "fast" diffusion. The high activation energy for "fast" diffusion is due to an interaction (association) o f the diffusing Na + ion with a ( N - S i - N ) group to form a N a - N - S i - N complex. The association energy for this complex is approximately 1.2 eV. We have observed only one region in the diffusion profiles in the oxygen-doped films. This region is due to "bulk" diffusion. The magnitude and activation energy for diffusion is strongly dependent upon the oxygen content. It decreases from approximately 1.8 to 1.3 eV when the oxygen content o f the film increases from 0% to 25%. These results are then used to discuss possible device reliability problems which m a y occur in oxygen-doped films. J W Osenbach and S S Voris, Jappl Phys, 63, 1988, 4494~4500. 23 6562. Ion-beam-induced desorption of Ar + ion clusters The mass distribution o f Ar + ion clusters desorbed from Ar solid at 20 K was measured for 1 ~< n ~< 38. The desorption was induced by bombardment of the solid by three different primary ions, Ne +, Ar +, and Kr +, at 6 keV. The mass distribution is not influenced greatly by the bombarding species. This agrees with the description of the experimental data by Rice, Ramsperger, Kassel, and Marcus ( R R K M ) theory incorporating the charge-transfer process. Certain "magic n u m b e r " cluster ions were also observed in the Ar + mass distribution. J W Christiansen et al, J Vac Sci Technol, A6, 1988, 699-702. 23 6563. Contamination effects in glow discharge deposition systems The slow release of reactive gases from the walls and electrodes of practical plasma enhanced chemical vapor deposition (PECVD) systems has been studied. These desorption effects become important when thin films with different compositions are sequentially deposited in single-chamber deposition systems. The pressure rate of rise o f a P E C V D reactor was measured after exposure of the system to commonly used precursor gases. The nature of the gas, its pressure, the system temperature, and the time duration of the exposure are experimental variables. Contamination effects by dopants at the parts per million level were investigated by their effect on the electrical properties of subsequently deposited films. It is found that a m m o n i a and diborane, both of which are extensively used for device fabrication, are especially difficult to remove from the system. Operational procedures such as long p u m p o u t times, baking, and short exposure times to the gases, preferably at low pressures, can often reduce the extent of the carryover to an acceptable level in a single-chamber system. However, the use of multichamber systems is likely to be the most effective solution to crosscontamination problems in P E C V D processes. Frank Jansen and Dan Kuhman, J Vac Sci Technol, A6, 1988, 13 18. 23 6564. Mechanical property and structure relationships in hard coatings for cutting tools The trends in the use of hard protective coatings in W C Co metal cutting inserts are reviewed in light of recent evaluations of mechanical and structure-sensitive properties such as elevated temperature microhardness, microfracture toughness, and internal stress. A better understanding of the role of hard coatings has evolved due to development of reliable methods to measure mechanical properties of thin coatings (of the order of 5/z thick). There are intrinsic differences in the microstructure and residual stress state of chemical and physical vapor deposited (CVD and PVD) hard coatings. High compressive residual stress and fine grain size in PVD coatings contribute to increased microhardness and microfracture toughness. However, these benefits are reduced at high temperatures. Certain well-known structure/property concepts in bulk materials are shown to be applicable to hard coatings, which aid in interpretations of metal cutting wear behavior. Dennis T Qninto, J Vac Sci Technol, A6, 1988, 214~2157. 23 6565. On the existence of point defects in physical vapor deposited films of TiN, ZrN, and HfN Sets of experimental data from a n u m b e r of different techniques are summarized in the present work. They indicate that lattice defects in the form of vacancies and interstitials are very often present in films of the group-IVB nitrides as prepared by plasma enhanced physical vapor deposition methods. Lattice parameters, even allowing for the presence of residual stresses, density and positron annihilation data and the effect of deposition conditions on the reflectance and color of films, together with the effects of tempering, indicate that the fraction of interstitials