Soft lithography: Micro- and nanofabrication based on microcontact printing and replica molding.

摘要

Chapter 1 describes the use of microcontact printing ({dollar}mu{dollar}CP) with an elastomeric stamp for generating patterned self-assembled monolayers (SAMs), and the subsequent use of these patterned SAMs as ultrathin resists (2-3 nm) for pattern transfer in micro- and nanofabrication. The patterned SAMs are efficient resists that protect the underlying substrates from dissolution in selective etchants (for example, for evaporated thin films of Au, Ag and Cu, aqueous solutions containing {dollar}rm Ksb2Ssb2Osb3, Ksb3Fe(CN)sb6 and Ksb4Fe(CN)sb6).{dollar} The patterned SAMs can also be used as templates for selective deposition of conducting polymers by in situ polymerization, and of metals by chemical vapor deposition (CVD), electroplating and electroless deposition.; Chapter 2 describes several methods that generate patterned relief structures for casting the elastomeric stamps required in microcontact printing. The relief structures include the following: patterns etched in a thin film of Ag (200 nm thick); patterned polymeric structures assembled on the surface of a thin film of Ag (or Au); self-assembled polystyrene microspheres; an array of micrometer-sized channels etched in glass; patterned relief microstructures generated in a thin film of wax by micromachining; and V-shaped microstructures or pyramidal cavities anisotropically etched in a Si(100) wafer. Commercial diffraction gratings were also useful as masters. These procedures provide a convenient route to moderately complex patterns of SAMs with feature sizes ranging from {dollar}sim{dollar}100 nm to {dollar}sim{dollar}100 {dollar}mu{dollar}m.; Chapter 3 describes the use of replica molding of organic polymers against elastomeric masters in micro- and nanofabrication. Complex optical surfaces (such as a blazed, chirped diffraction grating on a curved surface) can be fabricated by replicating relief structures present on the surface of an elastomeric master with an ultraviolet- or thermally-curable organic polymer, while the master is deformed by compression, bending, stretching, or a combination of them. Using a similar procedure, it has been possible to produce many polymeric nanostructures ({dollar}sim{dollar}50 nm in dimension) from a single master with an accuracy better than {dollar}pm{dollar}5 nm. We also have been able to reduce the size of certain features from {dollar}sim{dollar}50 nm to {dollar}sim{dollar}30 nm by replica molding against an elastomeric master with mechanical bending. This simple, low-cost procedure represents a practical step toward manufacturing of nanometer-sized structures.; Chapter 4 describes the use of micromolding in capillaries (MIMIC) to produce complex polymeric microstructures supported on different substrates, and the applications of these microstructures in microfabrication. We formed patterned microstructures of organic polymers--polyurethane, polyacrylate, epoxy, conducting polymers and ceramics--by molding in enclosed, continuous channels formed by conformal contact between a solid support and an elastomeric mold whose surface had been patterned with a relief structure having mm-scale dimensions. The patterned polymeric microstructures formed on SiO{dollar}sb2,{dollar} glass and metals (Au, Ag and Cr) could be used directly as resists in the selective etching of underlying substrates. Free-standing polymeric microstructures fabricated by lift-off were used as disposable masks to generate patterned microfeatures of metals on the surfaces of both planar and non-planar substrates.; "It is soft because it is not hard to do!"