We have characterized the phase behavior of mixtures of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and the organic salt 3-sodium-2-hydroxy naphthoate (SHN) over a wide range of surfactant concentrations using polarizing optical microscopy and X-ray diffraction. A variety of liquid crystalline phases, such as hexagonal, lamellar with and without curvature defects, and nematic, are observed in these mixtures. At high temperatures the curvature defects in the lamellar phase are annealed gradually on decreasing the water content. However, at lower temperatures these two lamellar structures are separated by an intermediate phase, where the bilayer defects appear to order into a lattice. The ternary phase diagram shows a high degree of symmetry about the line corresponding to equimolar CTAB/SHN composition, as in the case of mixtures of cationic and anionic surfactants.

No abstract

No abstract

Experiments show that pure copper films can be formed at temperatures below 190 °C by H2 plasma assisted chemically vapor deposited copper(II)-hexafluoroacetylacetonate. A fundamental surface reaction mechanism has been derived for the reaction between dissociatively adsorbed precursor and atomic hydrogen produced in the plasma. The mechanism suggests that the deposition rate is proportional to [Cu(HFA),] 1/2 [H] and film purity improves with an increase in atomic hydrogen concentration. A new lumped parameter model has also been developed that agrees very well with experiments, to relate the operating conditions to the concentrations of Cu(HFA)2 and atomic hydrogen. Our model shows that at temperatures above 200 °C, surface recombination of atomic hydrogen decreases adsorbed [H] leading to copper films possessing high resistivity. It also indicates that at plasma powers above 60 W, high electron concentrations lead to the gasphase decomposition of the precursor and high film resistivity. An apparent activation energy of 5.0 kcal/mol is also suggested for the deposition, by the experiments and the reactor model.

The transport of Al into Cu is studied by annealing Cu/Al/SiO2 bilayers. In order to minimize the effects of contaminants, samples were prepared and annealed in all-metal ultrahigh vacuum systems. In situ resistivity was used to continuously monitor the transport of Al into the bulk of the copper films. It is observed: that Al begins to move into the copper at low temperature (100–150 °C); that during an isothermal anneal, there is an initial rapid increase in Al concentration in the copper followed by a very slow increase; the equivalent of about 45 A of Al remains bound at the SiO2 interface or at the surface of the copper and is not free to dissolve in the copper. These data are not consistent with simple one-dimensional bulk diffusion but are in good agreement with a model of three-dimensional copper grains in which there is rapid transport to saturate the grain boundaries followed by diffusion of Al from the grain boundaries into the copper grains. One important observation is that because of the role of grain boundaries, it is possible to transport Al through copper films without a significant increase in the resistivity of the copper films. The potential application of this system for microelectronic interconnects in modern microelectronics is discussed.

Low resistivity (≈2.2–3.0 μΩ cm), high purity copper films have been deposited by the hydrogen plasma assisted chemical vapor deposition of copper(II) hexafluoroacetylacetonate, Cu(Hfa)2, at pressures of 1.0–3.0 Torr, substrate temperatures of 160–240 °C, plasma powers of 3.0–15.0 W and precursor mole fractions of 0.25%–0.8%. The film purity and morphology have been analyzed by X-ray photoelectron spectroscopy, scanning electron microscopy and X-ray diffraction. Under the conditions investigated, the film growth rates were measured to be in the range of 40.0–200.0 Å/min. The experiments suggest that the deposition rate, precursor conversion, film purity and morphology can be tailored by adjusting the operating conditions appropriately. Our results have been used in conjunction with a reactor model of plasma assisted chemical vapor deposition to suggest operating conditions for high copper growth rates and high purity.

No abstract