Microcontact printing (μCP) is the first soft-lithographic technique developed by Kumar and Whitesides in 1993. At first, it was mainly used to pattern thiol self-assembled monolayers on metal surfaces, but later on, has been applied to various materials, including biological molecules. Because of its wide application, the μCP is considered to be not only a patterning technique, but also used as a convenient soft-manufacturing method. In this article, basics and recent topics of the μCP are overviewed. Main technical developments are targeting on the biological applications and the fabrication of organic transistors. We introduce up-to-date technical achievements of the both fields. In addition, efforts to scale down the pattern resolution and unique applications utilizing the properties of the stamp material are mentioned.
Recent ultra-large-scale integration (ULSI) production processes involve fabricating sub-0.1-μm patterns on Si wafers. High-density plasma sources are key technologies for developing precise etching processes. The disadvantages of these technologies include several types of radiation damage caused by the charge build-up of positive ions and electrons or by ultraviolet and X-ray photons during etching. These are very serious problems that must be overcome in the fabrication of future nanoscale devices. To overcome these problems and achieve accurate nanoscale patterning, a high-performance neutral-beam etching system is required.
Nanoimprint lithography (NIL), by which resist patterns are fabricated by deforming the physical shape of the resist by embossing with a mold, is a very useful lithography technique. This has been demonstrated for making nanostructure devices such as a quantized magnetic disk. This technique has excellent features, such as being able to create lithographic printing that is sub-10 nm in size over a large area. NIL has increasingly been recognized as a key nanomanufacturing technology that will play a critical role in commercialization of nanostructures. NIL is opening up many opportunities, because of sub-10 nm resolution in both feature size and critical dimension control, low-cost, high-throughput, large area, high fidelity, and excellent repeatability. This article overviews a recent development of NIL and related technologies such as soft lithography.
Aerosol deposition (AD) is a novel ceramics coating method based on shock-consolidation of fine powder jet follow at room temperature. In this paper, overview of particular features and application to MEMS devices, RF-components, and optical devices on AD were reported.
A variety of functions of nanoparticle thin films are expected to be realized by two- or three-dimensional ordering of a large number of nanoparticles. The coating-drying process that induces a self-ordering of nanoparticles in a liquid phase is one of the most promising methods for industries. However, the structures of ordered nanoparticles are designed by empirical control of some process conditions in industries. We have modeled the dynamics of two-dimensional self-ordering of nanoparticles in a liquid phase, and have simulated the drying processes of nanoparticle suspensions. The relationships between the process conditions and the structures are derived from the simulation results as well as some experimental data. We have proposed three non-dimensional variables to represent principles of the two-dimensional self-ordering of nanoparticles: 1) Long-range inter-particle energy ratio, 2) Particle binding energy ratio, 3) Particle travel time ratio. These variables are functions of some process conditions, and the structures of ordered nanoparticles can be estimated by sets of these variables.
The combination of self-, directed and positional assembly techniques, i. e., “bottom up” fabrication, is demonstrated in this work because they will be essential for patterning and connecting future nanodevices. An array of polystyrene spheres was used instead of conventional lithographic techniques to make “parent” structures. A close-packed monolayer of polystyrene spheres (diameter∼400 nm) was used as a hard mask. Gold was vapor deposited through this mask and lift-off of the spheres produced arrays of triangular gold dots, which were used as “parent” structures. Multilayers of 16-mercaptohexadecanoic acid and Cu2+ ions were selectively deposited as a molecular resist onto these gold dots followed by chromium deposition creating a daughter structure on the substrate. After lift-off of the molecular resist, uniform spacings between “parent” and “daughter” structures are observed using a scanning electron microscope. Nanometer-scale spacing can be controlled around the nanostructures by simply changing the number of layers in the molecular resist or by using molecules of different lengths. In the near future, many applications using this method are expected to impact nanofabrication, such as nanoelectronic devices and micromachines.
A new technique for preparing cross-sections was developed on unembedded in supporting medium and structural elements unchanged with paper and printed paper. In this method, a focused ion beam (FIB) was irradiated to it. The FIB technique was applied as an improved method to various papers and printed papers. As a result, smooth cross-sections of paper and printed paper composed of materials with different hardness were successfully prepared and the micro-photograph without structural change or artifact was satisfactorily obtained. Further, clear image of the printed ink transferred to paper was observed for the first time by this method. However, penetration behavior of the ink vehicle into the substrate structure could not be directly observed through scanning electron microscope (SEM), because there is no generation of contrast between the printing vehicle and the printed paper. Hence, in order to obtain useful information on interaction between the substrate structure and the ink of the printed paper, a new technique was developed by combining FIB method with electron probe micro analyzer (EPMA) measurement after osmium labeling of the unsaturated carbon double bonds in the vehicle. A distribution of the vehicle transference and penetration into the paper could be observed using the new method.