Seminars & Colloquia

SPECIAL JOINT PHYSICS – CHEMISTRY COLLOQUIUM

Supercritical Fluid Technology for the Fabrication of Nanostructured Devices: Deposition of Metals and Mesoporous Silicates from Carbon Dioxide

Prof. James J. Watkins
Department of Chemical Engineering
U Mass Amherst

Wednesday, October 29, 2003
4:00 pm, Higgins 310
Refreshments precede the talk, Higgins 230, 3:30 pm

Supercritical fluids (SCFs) including carbon dioxide offer a unique technology platform for the fabrication of devices having feature dimensions in the sub-100 nm regime. This talk will describe SCF-based processes for metal deposition and the formation mesoporous silicate films for fabrication of devices with controlled architectures, including microelectronic devices, sensors, separation media and photonic materials. The preparation of Cu interconnect structures in advanced integrated circuits will be used as an illustrative example and other applications will be discussed.

As interconnect dimensions recede below 90 nm, the deposition of defect-free high purity Cu films within high aspect ratio features becomes a significant challenge. Recently we demonstrated these demands can be met using chemical fluid deposition (CFD), a new approach that involves the chemical reduction of organometallic compounds in supercritical carbon dioxide. Reduction of Cu(II) or Cu(I) precursors with H2 or alcohol yields remarkably pure films with resistivities as low as 2.0 microohm-cm, well within standards required by the International Technology Roadmap for Semiconductors. CFD can also be used for the deposition of other technologically important metals including Pt, Pd, Au, Ni, Co and their alloys using appropriate precursors. For example, we recently deposited continuous Pd films deep within porous supports for membrane applications.

Reduced interconnect dimensions will also place greater demands on dielectrics, requiring the development of robust, mesoporous films. Here we describe a new approach to mesoporous silicates that involves the infusion and selective condensation of metal oxide precursors within one phase domain of a highly ordered, preformed block copolymer template dilated with supercritical carbon dioxide. The template is then removed to produce the mesoporous oxide. To date we have replicated ordered spherical and cylindrical morphologies to yield silica, organosilicate and mixed silica/organosilicate mesostructures in films over 1 micron thick while maintaining all the structural details of the sacrificial copolymer template. One advantage of the process is the elimination of excess alcohol from the reaction media, which provides a pathway for rapid and high degrees of network condensation. Moreover, separation of the template formation and infusion steps is enabling. Ultimately, structure on both the local and device levels can be achieved in three dimensions wholly in the polymer template using established techniques prior to infusion of the inorganic phase. Control over mesoporous oxide structures is enabling for a number of applications. For example oriented arrays of cylindrical nanopores would find application in catalysis, sensors and separations. The approach is extendable to other metal oxides, including titania for optical applications.