Fabrication of Device Nanostructures Using Supercritical Fluids

Abstract

Supercritical fluids including carbon dioxide offer a combination of properties that are uniquely suited for device fabrication at the nanoscale. Liquid-like densities, favorable transport properties, and the absence of surface tension enable solution-based processing in an environment that behaves much like a gas. These characteristics provide a means for extending “top-down” processing methods including metal deposition, cleaning, etching, and surface modification chemistries to the smallest device features. The interaction of carbon dioxide with polymeric materials also enables complete structural specification of nanostructured metal oxide films using a “bottom-up” approach in which deposition reactions are conducted within sacrificial, pre-organized templates dilated by the fluid. The result is high-fidelity replication of the template structure in a new material. In particular, block copolymer templates yield well-ordered porous silica and titania films containing spherical or vertically aligned pores that can serve as device substrates for applications in microelectronics, detection arrays, and energy conversion. Finally, the synthesis of nanoparticles and nanowires in supercritical fluids is developing rapidly and offers promise for the efficient production of well-defined materials. In this review, we summarize these developments and discuss their potential for nextgeneration device fabrication.

Design of functional nanostructured materials using supercritical fluids

“…Taking the desirable attributes of CVD and aqueous plating techniques while minimizing the disadvantages of each, chemical fluid deposition (SCFD) is also used to modify the surface properties of organic and inorganic materials. This method was first used for the synthesis of nanosized thin metal films (platinum and palladium) onto silicon wafers and polymers substrates (poly-(tetrafluoroethylene), Kapton polyimide and Anopore aluminum oxide membrane) by the reduction of appropriate metal precursors with hydrogen in scCO 2 [39]. The films were found to be essentially free from ligand-derived contamination and exhibited excellent conformity on patterned surfaces.…”

A comparative study of copper thin films deposited using magnetron sputtering and supercritical fluid deposition techniques

“…Supercritical fluid chemical deposition (SFCD) process mainly developed with supercritical carbon dioxide (scCO2) can also be an alternative method that enables the fabrication of nanostructured films in an environmentally friendly manner and from a scalable technology [10][11][12][13][14]. SCFD technique is a one-pot, multi-step process that involves, the dissolution of a metallic precursor in a supercritical fluid followed by a chemical reaction (i.e.…”

Supercritical Carbon Dioxide Drying of Methanol−Zinc Borate Mixtures

“…Supercritical fluids have been used in areas ranging from natural products extraction, materials cleaning, chemical reactions, nanoparticle preparation and drying. 11,12 The production of nanosized metal borates was studied using supercritical ethanol drying and supercritical CO 2 drying. 13,14 Supercritical CO 2 drying has been utilized in many applications owing to the fact that carbon dioxide is inexpensive, environmentally benign, not flammable, nontoxic and can be regenerated easily by a cycle system.…”