Applications constant materials

Early work in ellipsometry focused on improving the technique, whereas attention now emphasizes applications to materials analysis. New uses continue to be found however, ellipsometry traditionally has been used to determine film thicknesses (in the rang 1-1000 nm), as well as optical constants. " Common systems are oxide and nitride films on silicon v ers, dielectric films deposited on optical sur ces, and multilayer semiconductor strucmres. 

Neirynck, J. M., Yang, G. R., Murarka, S. P., et al., Low Dielectric Constant Materials-Synthesis and Applications in Microelectronics, Materials Research Society Symposium Proceedings, Vol. 381,1995,pp. 229-234. 

The CCS approach is well matched to the synthesis part of the problem of the identification of new thin-film high dielectric constant materials for embedded DRAM applications. As noted above, low-temperature deposition is essential and the CCS approach provides in situ mixing at low temperatures. Samples are obtained in thin-film form and can be made in thicknesses that are similar to those that will actually be used. 

Binary systems of course can be handled by the computer programs devised for multicomponent mixtures that are mentioned later. Constant molal overflow cases are handled by binary computer programs such as the one used in Example 13.4 for the enriching section which employ repeated alternate application of material balance and equilibrium stage-by-stage. Methods also are available that employ closed form equations that can give desired results quickly for the special case of constant or suitable average relative volatility. 

If the yield coefficient Y for the conversion of substrate into microbial cells is assumed to be constant, then when Monod kinetics are applicable the material... 

Since the discovery of ordered mesoporous materials, researchers have explored many possible applications that can take advantage of the unique compositional or structural features of mesoporous materials. In addition to apphcations in traditional areas such as catalysis, separation, and ion exchange, new applications that might involve mesoporous materials include stationary phases in HPLC, bio and macromolecular separations, low dielectric constant materials, enzyme immobilization, optical host materials, templates for fabrication of porous carbons, and reactions in confined enviromnents. 

H. Treichel, B. Withers, G. Ruhl, P. Ansmann, R. Wurl, Ch. Muller, M. Dietlmeier, and G. Maier, Handbook of Low and High Dielectric Constant Materials and their Applications, Vol.l, 1999, p.l. 

Some other interesting applications include the CMP of high dielectric constant materials (e.g., BaTiOj) that could be used for increasing capacitance, high T -superconductors used for zero-resistance interconnections, and optoelectronic materials, especially waveguides, where surfaces will play an important role. There is considerable interest in these areas and there are quite a few challenges to encounter in each case. Unfortunately, very little is disclosed in the published literature. We shall review and discuss each of these areas in the following, with more focus on areas of immediate interest to microelectronic industry, the areas (a), (b), (c), (d), and (h). 

Comparison of the properties of CSD thin films to the analogous bulk material properties has also received great attention because of the need for high dielectric constant materials for DRAM applications.Basceri et ai 134,135 jj yg thoroughly considered the differences between film and bulk properties from a fundamental perspective and have been able to interpret these differences in terms of stresses present in the films, compositional differences, and the impact of these characteristics on the phenomenological behavior of the material as predicted from a Landau-Ginzburg-Devonshire approach. All observed differences between film and bulk properties were explainable using this approach. 

Recent improvements in techniques of sedimentation and diffusion analysis have permitted their application to materials in the molecular-weight range of the Schardinger dextrins. These measurements supplement other types of determinations in that (1) they are not particularly sensitive to the presence of low molecular-weight impurities, and (2) the sedimentation and diffusion constants can be extrapolated to infinite dilution to eliminate aggregation and interaction effects. 

In the application of the heat conduction equation in its general form (2.8) a series of simplifying assumptions are made, through which a number of special differential equations, tailor made for certain problems, are obtained. A significant simplification is the assumption of constant material properties A and c. The linear partial differential equations which emerge in this case are discussed in the next section. Further simple cases are... 

Ordered macroporous materials with pore sizes in the sub-micrometer range have applications in low-dielectric-constant materials and lightweight structural materials. Macroporous oxides such as silica, titania, and zirconia as well as polymers with well defined pore sizes in the sub-micrometer regime have been successfully synthesized.[166,167]... 

Aromatic polyimides have found extensive use in electronic packaging due to their high thermal stability, low dielectric constant, and high electrical resistivity. Polyimides have been used as passivation coatings, (1) interlayer dielectrics, (2) die attach adhesives, (3) flexible circuitry substrates, (4) and more recently as the interlevel dielectric in high speed IC interconnections. (5) High speed applications require materials with a combination of low dielectric constant, flat dielectric response versus frequency and low water absorption. 

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