Thin-film multilayer processing

Figure 17. Subtractive approach for processing thin-film multilayer structures.

An important theme of this volume is the interrelationships among materials chemistry, photonic and optoelectronic properties, and device performance. The design and synthesis of novel polymer compositions and architectures aimed at enhanced properties are emphasized in some chapters. Other contributions feature the development of novel approaches to processing and fabrication of photonic and optoelectronic polymers into thin films, multilayers, fibers, waveguides, gratings, and device structures. These approaches, which emphasize polymer synthesis, processing, and device fabrication, are complementary and synergistic. 

In all but the simplest electronic circuits, it is necessary to have a method for fabricating multilayer interconnection structures to enable all the necessary points to be connected. The thick film technology is limited to three layers for all practical purposes because of yield and planarity considerations, and thin-film multilayer circuits are quite expensive to fabricate. The copper technologies can produce only a single layer because of processing limitations. 

The use of UPD layers can in principle generate deposits with composition modulated on the atomic scale, and Pauling et al. have produced what they call hetero-structured ultra-thin films containing Ag, Pd and T1 by this method [158], Stickney and coworkers have assembled multilayered deposits of CdTe and GaAs by addition of one atomic layer of the individual components at a time, a process they call electrochemical atomic-layer epitaxy [159 162], The essential controlling feature in the UPD mechanism is that the deposited layers are allowed to reach equilibrium. Hence, the process represents an extreme of local, reversible control. 

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