Barrier layer

About: Barrier layer is a research topic. Over the lifetime, 21843 publications have been published within this topic receiving 229167 citations.

The formation of controlled-porosity membranes from anodically oxidized aluminium

Abstract: Synthetic membranes are used in a number of diverse applications, such as filtration1,2, bioreactors2,3, tissue culture4, analytical devices including sensors2,5, and as supports for active materials1,5. Narrow pore-size distribution, high pore density and thinness are often important attributes. The anodic oxidation of aluminium6 can produce porous films possessing these features; the anodizing voltage controls the pore size and pore density, whereas the thick-ness is determined by the amount of charge transferred. A major problem with this technique, however, is that the films remain attached to the aluminium, with the pore base closed by an oxide barrier layer. Here we overcome this problem by progressively reducing the anodizing voltage, thereby causing perforation of the barrier layer and separation of the film as a porous membrane.

Evidence of the barrier layer in the surface layer of the tropics

Abstract: Comparisons between isothermal depth to the top of the thermocline, and the mixed layer depth based on a ot criterion were undertaken for the tropical world oceans. In three equatorial regions, a shallower mixed layer than isothermal layer occurs, implying the presence of a strong halocline above the thermocline. This distance separating the top of the thermocline and the bottom of the mixed layer is referred to as the "barrier layer", in relation to its impediment to vertical heat flux out of the base of the mixed layer. Different mechanisms are responsible for maintaining the barrier layer in each of the three regions. In the western equatorial Pacific Ocean a salinity budget confirmed that heavy local precipitation most likely results in the isothermal but salt-stratified layer. In the northwest equatorial Atlantic, it is hypothesized that high salinity waters are subducted at the subtropics during winter and advected westward as a salinity maximum in the upper layers of the tropics, resulting in the barrier layer. In the eastern equatorial Indian Ocean, monsoonal related rainfall and river runoff contribute significantly to the freshwater flux, producing salt stratification in the surface. These results suggest the need to include the effects of salinity stratification when determining mixed layer depth.

Selective electroless copper deposited interconnect plugs for ULSI applications

Abstract: A method or utilizing electroless copper deposition to selectively form encapsulated copper plugs to connect conductive regions on a semiconductor. A via opening in an inter-level dielectric (ILD) provides a path for connecting two conductive regions separated by the ILD. Once the underlying metal layer is exposed by the via opening, a SiN or SiON dielectric encapsulation layer is formed along the sidewalls of the via. Then, a contact displacement technique is used to form a thin activation layer of copper on a barrier metal, such as TiN, which is present as a covering layer on the underlying metal layer. After the contact displacement of copper on the barrier layer at the bottom of the via, an electroless copper deposition technique is then used to auto-catalytically deposit copper in the via. The electroless copper deposition continues until the via is almost filled, but leaving sufficient room at the top in order to form an upper encapsulation layer. The SiN or SiON sidewalls, the bottom barrier layer and the cap barrier layer function to fully encapsulate the copper plug in the via. The plug is then annealed.

Porous anodic film formation on aluminium

Abstract: The development of porous anodic films on aluminium in the major forming acids has been established1–5 However, little information has been provided to explain the markedly different rates of steady-state film growth for anodizing in constant voltage conditions in these acids, with the anodic film cell parameters dependent on the cell voltage1 The regular cellular morphology of the steady-state films and the substructure developed in the forming acids are revealed in Fig 1 The characteristic parallel-sided pores, at the centres of approximately hexagonal cells, pass normal to the macroscopic metal surface but are separated from it by the barrier layer Here, from considerations of the film material substructure and the distribution of species within the film derived from the forming acid, it is postulated that the likely variations in the local field strengths across the barrier layers can explain the steady-state anodizing behaviour observed in the different acids in constant voltage conditions