VLSI electronic circuits

Photoresists and electron-beam resists are the key to the success of VLSI electronic circuits. Without these resists, most electronic equipment would not exist. These polymers are spun onto the semiconductor and exposed to the circuit pattern leading to main chain scission or crosslinking. Subsequently, unpolymerised sections are removed. This process is employed either in wet or in dry conditions. This is known as the photolithographic process, which is part of the semiconductor fabrication technology. Further treatment includes diffusion of various semiconductor elements and metallisation for conduction lines. Layer by layer, the total package is developed. Current research is now directed toward finer features in the patterns and changes in the surface characteristics for subsequent layers. 

Similarly, many reactors with integrated mixers and other functionality can be manufactured on one substrate to form, e.g., a combinatorial synthesis platform. Such microfluidic platforms may approach the complexity of VLSI electronic circuits, see e.g. [64], which gives an example fabricated by soft lithography (imprinting) in the polymer PDMS or [65], which gives an example in laser-machined laminated Mylar sheets. The combinatorial aspect of these examples consists in mixing chemicals in different ratios to achieve concentration series in a discrete way (i.e. a different concentration for each microchannel) which are subsequently used in a chemical reaction on the same microfluidic chip. 

Aromatic polyimides have gained wide popularity as dielectric materials in a variety of applications in the manufacturing of electronic circuits due to their thermal, mechanical and electrical properties. Most notable among these applications are as interlayer dielectrics in multilevel VLSI circuits and in multilevel interconnects, as well as in the packaging of integrated circuits. 

Polymer radiation chemistry is a key element of the electronics industry, in that polymer materials that undergo radiation induced changes in solubility are used to define the individual elements of integrated circuits. As the demands placed on these materials increases due to increased density, complexity and miniaturization of devices, new materials and chemistry will be required. This necessitates continued efforts to understand fundamental polymer radiation chemical processes, and continued development of new radiation sensitive materials that are applicable to VLSI Technology. 

The fabrication of LSI circuits, and of VLSI circuits in particular, requires patterns of micron and submicron dimensions, and consequently polymer resists with a high degree of resolution (1). So far the most frequently used positive electron resist has been poly(methyl methacrylate) (PMMA), which affords a high resolution power together with a relatively good thermal stability (2-4) A serious limitation of PMMA with respect to the efficiency of the electron lithography system is its low sensitivity to electron irradiation ( 10-5 - 10 4c/cm2). For the preparation... 

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