Minute wiring technology using nano-sized particles

Abstract

Nanoscale metal particles have been of great interest in the development of next generation micro- and nano-electronics devices. In this review, we describe the characteristics and applications of monolayer-protected metal nanoparticles as well as importance of controlling their surface and interfacial structures for electronics applications, on the basis on our recent experimental results. Recently, much effort has been devoted to directing monolayer-protected metal nanoparticles into organized structures onto solid supports by a variety of fabrication techniques. One of the emerging techniques for immobilization is to use organic monolayers attached on the nanoparticles and substrate of interest to guide the assembly of the nanoparticles through predesigned chemical and physical interactions. We demonstrate a novel technique for the fabrication of two-dimensional microscopic assembly of monolayer-protected gold nanoparticles onto substrates. Selective integration of the nanoparticles onto either hydrophobic or hydrophilic region on the substrates could be achieved by controlling dispersion-aggregation process of gold nanoparticles, thereby providing effective methodology for fabrication of various patterns of integrated mesoscopic nanoparticle assemblies that can be further used for development of metallic circuits. Our next interest is to develop simple strategy for fabrication of metallic circuits on polymeric substrate, with high adhesive strength achieved via novel concept of nanoscale interlocking mediated by metal nanoparticles. We proposed novel process for forming metallic circuit patterns on polyimide substrate, which has excellent electrical, thermal, chemical and dielectric properties. The process involved a surface modification of polyimide, incorporation of metallic ions followed by reduction to form thin films consisting of metal nanoparticles. We have succeeded to fabricate metallic silver and copper circuit patterns that are highly adhesive due to the interlocking mediated by metal nanoparticles at metal/polymer interface. The interfacial structures presented here are promising for future miniatulization of metallic circuit patterns in microelectronic devices. © 2005 The Japan Institute of Metals.