Microelectronics multilayer films

To our knowledge, the present polyimide monolayer films possess the minimum thickness ever produced. We believe that this simple and efficient method for the preparation of polyimide mono- and multilayer films will bring about new technology especially in microelectronics. 

Equally important as tape casting in the fabrication of multilayer ceramics is thick film processing. Thick film technology is widely used in microelectronics for resistor networks, hybrid integrated circuitry, and discrete components, such as capacitors and inductors along with metallization of MLC capacitors and packages as mentioned above. 

In numerous applications of polymeric materials multilayers of films are used. This practice is found in microelectronic, aeronautical, and biomedical applications to name a few. Developing good adhesion between these layers requires interdiffusion of the molecules at the interfaces between the layers over size scales comparable to the molecular diameter (tens of nm). In addition, these interfaces are buried within the specimen. Aside from this practical aspect, interdififlision over short distances holds the key for critically evaluating current theories of polymer difllision. Theories of polymer interdiffusion predict specific shapes for the concentration profile of segments across the interface as a function of time. Interdiffiision studies on bilayered specimen comprised of a layer of polystyrene (PS) on a layer of perdeuterated (PS) d-PS, can be used as a model system that will capture the fundamental physics of the problem. Initially, the bilayer will have a sharp interface, which upon annealing will broaden with time. 

Thin films of phthalocyanine compounds in general, and those prepared by the LB method in particular, display novel electrical properties (Baker, 1985). The LB technique for depositing mono- and multilayer coatings with well-controlled thickness and morphology offers excellent compatibility with microelectronic technology. Such films have recently been reviewed for their potential applications. The combination of LB supramolecular films with small dimensionally comparable... 

Most microelectronic facilities can readily achieve minimum feature sizes on the order of 10 pm or better. State-of-the art facilities can produce devices with feature sizes of a few tenths of a micrometer. The lower limit is still decreasing, but the effort required expands exponentially as feature size decreases. Frequently, large numbers of devices can be simultaneously fabricated on the same substrate and subsequently separated by scoring and breaking or sawing the substrate after all processing steps are complete. While complex multilayer devices are possible, most film electrode devices reported to date involve only one or two layers. 

Interesting and useful areas of research are possible when only minute amounts of material are available (sub)milligram-scale synthesis, fractions, explosives, nanostructures, microelectronics, additives, contaminants, multilayers, coatings, thin films, skin-core problems in the case of chemicals, materials, products, but also in challenging areas like e.g. forensic studies. 

Various multilayer dielectric films are commonly used in microelectronics, including, for example, combination oxides Si3N4-Si02. Combination oxides, which consist of a thin thermal Si02 layer (to achieve interface properties equivalent to thermal Si02> followed by sputtered bulk oxide (produced at low temperatures), were studied by IR spectroscopy [294]. The peak position and the FWHM of the stretching mode of combination oxides only differ by 6-8 cm from those of dry thermal oxides. This minor deviation indicates that the combination oxides and thermal ones have a comparable stoichiometry. 

Besides the value of LB-films as model systems in fundamental research there are a number of potential applications for these layers. The incorporation of LB monolayers and multilayers into both metal/LB-film/metal and metal/LB-film/semiconductor (MIS) devices has recently been attracting considerable attention [237]. Structures in the first category may find application as the basis for simple photovoltaic cells or switches. When deposited onto semiconducting substrates, the fine control of the LB layer thickness permits the optimization of the efficiency of both photovoltaic and electroluminescent structures. Thicker films can be used to control the surface conductivity of a variety of semiconductors and as the basis for a field effect transistor. The three particular examples presented in this section should serve to indicate the usefulness of monomolecular insulating films in the field of microelectronics. 

ToF-ERD is a powerful technique for profiling multilayered, multielemental samples, and thin films as may be found in the microelectronic industry, to provide information about the film stoichiometry, homogeneity, surface, and interfacial properties, necessary to engineer the film to the desired functional properties. 

In addition to forming continuous organometallic multilayer thin films, we explored the LbL deposition of polyferrocenylsilane polyions onto, for instance, hydrophilically/hydrophobically modified substrates with the aim of building two-dimensionally patterned organometallic multilayers. In general, surfaces modified with microscopically patterned conducting, luminescent, or redox-active polymer films have potential use in microelectronic and optoelectronic devices and microsensor arrays. Area-selective deposition of polyferrocenylsilane polyions can be an attractive method to obtain two-dimensionally patterned redox active films, which may be used as electrochemically modulated diffraction gratings. ... 

There are many practical microelectronic device configurations that are based on epitaxial semiconductor thin films. Heteroepitaxial thin films are also used in magnetic recording media, such as computer hard disks an example is described in Section 1.4.4. Epitaxially grown multilayer structures are also used in planar array laser diodes, which serve as optical inter-connnects for short- and medium-range information transfer, and which offer potential for the development of new devices for such applications as solid... 

Fig. 4.32. Scanning electron micrograph of the metalhzation, diffusion barrier and ILD layers in a typical multilayer thin film structure used in microelectronic devices. Note the presence of a delamination crack at the interface between the Si02 ILD and the TiN diffusion barrier, the fracture along which can limit the yield and reliability of the device. The top layer is also Si the two outer layers of Si of the same thickness provide a symmetric multilayer structure within which the thin films are sandwiched. Each Si layer (only a small portion of which is shown in this figure) is approximately 600 fiia thick. Reproduced with permission from Dauskardt et al. (1998).

As a conclusion of this section, let us characterise briefly the electronic structure investigations of one more group of materials whose properties are greatly dependent on surface effects. These are thin films made from refractory carbides and nitrides. These films find applications in microelectronics, optics and as coatings for cutting tools and other complicated multilayered materials. Such films can be produced by different methods, such as thermal deposition or laser evaporation, (Morchan, 1982), molecular-beam epitaxy and cathode sputtering (Herman, 1982 Cho, 1983), plasma condensation in vacuum with ionic bombardment of the substrate surface (Dorodnov and Potrosov, 1981), chemical vapour-phase deposition (Anikeev, 1977 Anikin, Anikeev and Zolotaryova, 1979), etc. 

R. G. Pond and W. A. Vitriol, Custom Packaging in a Thick Film House Using Low Temperature Cofired Multilayer Ceramic Technology, Proc. 1984 Int. Symp. on Microelectronics, 1984, pp. 268-271. 

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