ELECTROCHEMICAL NANOFABRICATIONS: A GENERAL REVIEW
Nanofabrications have been largely used in various applications such as photovoltaics, sensors, catalysts, integrated circuits, electronics, micro-optics, and countless others. The methodology of nanofabrication can be generally divided into two types of processes: top-down and bottom-up. Top-down process refers to approaching the nanoscale from larger dimensions, such as lithography, nanoimprinting, scanning probe, and E-beam technique. In contrast, the bottom-up fabrication process builds nanoscale artifacts from the molecular level up, through single molecules or collections of molecules that agglomerate or self-assemble. Using a bottom-up approach, such as self-assembly enables scientists to create larger and more complex systems from elementary subcomponents (e.g., atoms and molecules). Generally speaking, top-down processes that transfer minute patterns onto material are more matured than Electrochemical Nanofabrication: Principles and Applications Edited by Di Wei Copyright © 2012 by Pan Stanford Publishing Pte. Ltd. www.panstanford.com
bottom-up processes. An exception is epitaxial processes that create layers through layer-by-layer growth with registry at the atomic level. Electrodeposition has traditionally been used to form highquality, mostly metallic, thin films for decades. By carefully controlling the electrons transferred, the weight of material formed can be determined according to Faraday’s law of electrolysis. It was shown that high-quality copper interconnects for ultra-large-scale integration chips can be formed electrochemically on Si wafer [1,2]. Electrodeposition has thus been shown compatible with state-of-the-art semiconductor manufacturing technology. The largest semiconductor companies, for example, IBM, Intel, AMD, and Motorola, are installing wafer-electroplating machines on their fabrication lines . The electrodeposition of Cu with the line width 250 nm was used in the mass production of the microprocessor Pentium III in 1998. In 2003, the line width of the CPU was reduced to 130 nm in Pentium IV. Electrochemistry was largely used in chip fabrication  and the packaging of microelectronics . However, compared with other nanofabrication techniques, electrochemical nanofabrication is still a maiden area, which needs further development and fulfillment.