Metal based device fabrication

Unlike silicon-based materials where selective reactants are of ultimate importance, and III-V and metallic materials where product volatility dominates etching considerations, selective etching of organic films is driven by incorporating the desired reactivity (or lack of it) into the film itself. In device fabrication all types of materials are present simultaneously and the process engineer must be aware of the important aspects of the chemistry of each material in addition to the gas phase reactions that produce chemically active species. It is hoped that the discussions presented here provide a basis for approaching such a complex chemical system and for critically evaluating studies which appear in the literature. 

The method nearest to electronic device fabrication is the nanoscale processing based on the anodic oxidation of semiconductors and metals. The following electrochemical reactions proceed after applying voltage between the probe and the substrate in the column of adsorbed water generated at the region between them in the air as shown in Fig. 17. 

This paper describes a process for activating polyimide surfaces for electroless metal plating. A thin surface region of a polyimide film can be electro-chemically reduced when contacted with certain reducing agent solutions. The electroactivity of polyimides is used to mediate electron transfer for depositing catalytic metal (e.g., Pd, Pt, Ni, Cu) seeds onto the polymer surface. The proposed metal deposition mechanism presented is based on results obtained from cyclic voltammetric, UV-visible, and Rutherford backscattering analysis of reduced and metallized polyimide films. This process allows blanket and full-additive metallization of polymeric materials for electronic device fabrication. 

Nanocomposites in the form of superlattice structures have been fabricated with metallic, " semiconductor,and ceramic materials " " for semiconductor-based devices. " The material is abruptly modulated with respect to composition and/or structure. Semiconductor superlattice devices are usually multiple quantum structures, in which nanometer-scale layers of a lower band gap material such as GaAs are sandwiched between layers of a larger band gap material such as GaAlAs. " Quantum effects such as enhanced carrier mobility (two-dimensional electron gas) and bound states in the optical absorption spectrum, and nonlinear optical effects, such as intensity-dependent refractive indices, have been observed in nanomodulated semiconductor multiple quantum wells. " Examples of devices based on these structures include fast optical switches, high electron mobility transistors, and quantum well lasers. " Room-temperature electrochemical... 

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