Interconnects, superconductors

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). 

The inorganic chemist investigates the materials made from the other one hundred and some elements on the periodic table, an enormous undertaking. But while these compounds are rich and intricate in their behaviors, they do not form long, interconnected chains like the hydrocarbons do, so their diversity is in their elemental composition. Inorganic materials form the rock and salty solutions of Earth, the planets, and all the materials of the stars. Inorganic chemists devise syntheses for semiconductors, superconductors, alloys, and many other new materials. 

The applications we discuss here, in magnets, power transmission, computer interconnections, Josephson devices and instrumentation, have almost all been studied before, during two decades of active work in applied superconductivity 41. Thought of simply as a standard superconductor with a higher transition temperature, YBaCuO does not by itself imply new kinds of applications, even though it may improve the commercial prospects for applications previously burdened by overhead costs associated with helium refrigeration. More novel applications may well emerge in the future. 

Another possible application for high temperature superconductors is as interconnects in computer systems with semiconducting devices (31). These could be called hybrid systems, since they involve both superconductors and semiconductors. In particular CMOS devices are well-known to have enhanced performance at 77 K and are thus potentially compatible with YBaCuO. 

For relatively short lines, as might be of interest in interconnections on a microcircuit chip, a lumped circuit analysis is appropriate, and the performance can be estimated from an RC time constant. Here it is not sufficient to consider only the interconnect line resistance in the total resistance R. The effective output impedance of the CMOS device also contributes and is a key feature which limits the leverage of the superconductor. 

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