Microelectronic Fabrication

 INTRODUCTION

This blog covers basic microelectronic fabrication processes for semiconductor and VLSI technologies, including photolithography, plasma and reactive ion etching, ion implantation, diffusion, oxidation, evaporation, vapor phase epitaxial growth, sputtering, and CVD. Advanced processing topics like next generation lithography, MBE, and metal organic CVD also are introduced. The physics and chemistry of every process are introduced along side descriptions of the equipment used for the manufacture of integrated circuits. the mixing of microelectronic fabrication processes for CMOS and bipolar VLSI circuits is introduced. Furthermore, the fabrication of MEMS (Micro electronical Systems) and nanotechnology devices is additionally discussed. The fabrication of next-generation nanoelectronics circuits is introduced.

Strategies

There are two strategies for fabrication of nanoelectronics circuit. One is that the top down fabrication strategy utilizing nanolithographies to realize nanometer resolution, such as X-ray lithography, e-beam lithography, ion-beam lithography, etc. Another strategy utilizes bottom-up self-assembly to integrate individual atoms and molecules into nanoelectronics circuits, like quantum-dot cellular automata (QCA), single electron transistors (SETs), spin electronics, carbon-nanotube (CNT) based transistors , nanowire cross-bar nanoelectronics circuits , bioelectronics [etc. for every category of nanoelectronics, we introduce their working rule ,design and fabrication in details.



        

Top-down approach

The most common top-down approach to fabrication involves lithographic patterning techniques using short-wavelength optical sources. A key advantage of the top-down approach—as developed within the fabrication of integrated circuits—is that the parts are both patterned and inbuilt place, in order that no assembly step is required . Optical lithography may be a relatively mature field due to the high degree of refinement in microelectronic chip manufacturing, with current short-wavelength optical lithography techniques reaching dimensions slightly below 100 nanometers (the traditional threshold definition of the nanoscale). Shorter-wavelength sources, like extreme ultraviolet and X-ray, are being developed to permit lithographic printing techniques to succeed in dimensions from 10 to 100 nanometers. Scanning beam techniques like electron-beam lithography provide patterns right down to about 20 nanometers. Here the pattern is written by sweeping a finely focused beam across the surface. Focused ion beams also are used for direct processing and patterning of wafers, although with somewhat less resolution than in electron-beam lithography. Still-smaller features are obtained by using scanning probes to deposit or remove thin layers.

Bottom-up approach

Bottom-up, or self-assembly, approaches to nanofabrication use chemical or physical forces operating at the nanoscale to assemble basic units into larger structures. As component size decreases in nanofabrication, bottom-up approaches provide an increasingly important complement to top-down techniques. Inspiration for bottom-up approaches comes from biological systems, where nature has harnessed chemical forces to make essentially all the structures needed by life. Researchers hope to duplicate nature’s ability to supply small clusters of specific atoms, which may then self-assemble into more-elaborate structures.

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