Interdiffusion barrier layer

Cathodes with a high electrochemical performance are typically based on cobalt- and iron-containing perovskites such as (La, Sr) 

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The SNMS depth profile (ion intensity as a function of sputter time) for the matrix elements of a Ba07Sr03TiO3 layer on a silicon substrate with Pt/Ti02/Si02 buffer layers is illustrated in Figure 9.8. Inhomogeneity of the perovskite layer was detected especially for Sr. Furthermore, an interdiffusion of matrix elements of the Ba07Sr03TiO3 layer and of the Pt barrier layer was observed. 

Due to the need to increase the packing density in VLSIs (very large scale integrated devices), thermally stable, low-resistive contacts are becoming more and more important. These should also act as interdiffusion barriers to prevent junction failures. TiN has become attractive for silicon technology because of its high conductivity and its excellent properties as a barrier layer. The efficiency of TiN to prevent aluminum diffusion into silicon in Al/TiN/Si trilayers was ascertained up to temperatures of 550°C[14]. 

One of the main objective to aim in realizing an interdiffusion barrier is to obtain a layer extremely adherent, dense, homogeneous, and with continuous thickness. 

One of the main objectives in creating an interdiffusion barrier is to obtain a layer that is extremely adherent, dense, homogeneous and with a consistent thickness. To date, several types of barrier materials have been tested in various studies TiN (Shu et al, 1996), AI2O3 (Yepes et al., 2006), YSZ (Zhang et al, 2009). 

Figure 7.4 shows the structure of an FBMR with plate-type Pd-Ag dense metal membranes for hydrogen production [8, 9]. Two-sided planar membrane panels are suspended vertically in the reactor. Each side of the panels consists of 25 pm thick Pd-Ag foil mounted on a porous stainless steel base with a barrier layer to prevent interdiffusion... 

Inorganic (non-polymer) basecoats can provide layers to aid in adhesion (adhesion layer or glue layer) of a film to a surface. For example, in the Ti-Au metallization of oxides, the titanium adhesion layer reacts with the oxide to form a good chemical bond and the gold alloys with the titanium. The layers may also be used to prevent interdiffusion (diffusion barrier) between subsequent layers and the substrate. For example, the electrically conductive compound TiN is used as a barrier layer between the aluminum metallization and the silicon in semiconductor device manufacturing. 

In some cases a barrier layer such as TiN is used to prevent interdiffusion during subsequent high temperature processing. 

The ceramic thermal barrier layer provides thermal protection to the underlying materials. Also, this layer works as a shield to protect the underlying metallic parts from erosion and corrosion. The metallic bond coat is to protect the underlying superaUoy substrate from oxidation, balance thermal mismatch between the topcoat and substrate, and prevent interdiffusion of elements in the substrate and bond coat. 

On the semiconducting side, the interfacial layer has two zones. The first zone lies within the evanescent tail of the metal. The second zone is the remaining region where, due to interdiffusion, a composition or doping different from the original bulk semiconductor exists. A similar description can be characterized on the metal side and the new alloyed metal zone may be of sufficient width to become the metal forming the barrier. This new interfacial metal can have different characteristics from the originally deposited metal. 

Chemical modifications of the layers after deposition open new opportunities to further tune the properties of the multilayers. The cross-linking of protein multilayers by different chemical reactions [124,206,207], and the photocross-linking of unsaturated bonds has already been cited [185,211,212,233-235]. Other examples of cross-linking reactions can be found in the literature devoted to ESA [116,197,307]. Cross-linking may be used for instance to improve the chemical [116,124,197,206,212,307], mechanical [197], and thermal [233] resistance of the films, reduce the interdiffusion between neighboring layers, or change the barrier properties of the multilayers [185]. 

The electroplated nickel (Ni) serves as a barrier between the copper and the gold. Ni on its own is a poor candidate for a solder pad coating as it oxidizes rapidly and its native oxide is very stable—chemically tough to dissolve or react away. Unoxidized Ni can alloy with tin, which means that it can be soldered. Were the gold deposited over the copper directly, the gold layer would begin to interdiffuse with the copper even at room temperature forming an... 

The final steps involve deposition of the interconnect metal (Figure 4.39, step s). Copper is now the metal-of-choice due to its more desirable electrical resistivity, relative to A1 (1.7 pO cm vs. 2.7 pQ cm, respectively) that was exclusively used in earlier ICs. Due to its low resistivity and high density, titanium nitride is an efficient barrier level that prevents surface oxidation of Cu, as well as the interdiffusion of Cu into adjacent layers. To yield the final multilayer IC shown in step t of Figure 4.39, steps (p)-(s) are repeated. Indeed, a long complex process that took weeks in the making. 

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