Application Of Edge Imprint Lithography In The Functional Materials

With the development of science and technology, more and morenano-meter-sized patterns have been applied to integrated circuits, informationstorages, displays, sensors, biochips, optical devices, microfluidic devices andmany other fields. These applications make that the nano-processing technologyhas been widespread concern in the modern scientific community and industry.The practice of patterning is also known as lithography—a multiple-stepprocess that typically begins with the design of a pattern in the form of a data setand ends with a patterned array of small features on the surface of a substrate.Depending on the application, the requirements for a successful lithographicprocess can vary substantially. The minimum feature size of a test pattern isusually the most obvious issue one must consider when selecting a properlithographic technique. In microelectronics, for example, the growing demand forhigher densities of integration, less power consumption, better performance, andreduction in cost has kept pushing the capability of photolithography down to the nano-meter scale. The state-of-the-art in high-throughput nanofabrication is adeep UV (at193nm) photolithographic tool that utilizes liquid-immersion opticsto pattern sub-50nm structures across a300mm (12in.) wafer. However, in manyother applications outside of electronics, both cost and throughput could becomemore demanding parameters than the minimum feature size.The template method is very attractive, which possesses the significantadvantages of low cost, high throughput, high reproducibility, and enviableresolution of a few nanometers over large areas. Nanostructures are fabricated bythe stamp with high-resolution patterns. However, one of the major challengeswith this method is fouling and damage of the stamp, which is rather slow andexpensive to fabricate.Using edge capillary force lithography, which is induced by incompletely fillingof the resist polymer and capillary force around the pattern on the stamp, wefabricated the structures with much higher resolution than the original template.This method is successfully applied to the organic or inorganic materials,2D or3D high-resolution structure, and the high-sensitive nanosensors.First, the unconventional soft lithography technique (SASL) has been used tofabricate TiO2patterns with feature sizes much smaller than that of the stamp.Based on SASL, the dimension of the TiO2pattern can be tuned fromsub-micrometer to nanometer scale by varying the concentration of P-TiO2, theevaporation time and temperature. These patterns fabricated by SASL may havepotential applications in photoelectric devices, photo-catalytic surfaces, magneticelements, and gas sensors. Second, unconventional two-step imprinting has been used to fabricatewell-defined micro/nanoscale hierarchical structures. Based on CFL, which avoidsusing costly nanoscale stamp, nanofabrication in the second imprint was carriedout with low-cost microscale stamp. The effect of pressure, time and temperatureon the hierarchical structures in the second imprint has been investigated. Thesehierarchical structures fabricated by the method may have potential applications indiverse biomimetic, photonic, electronic/optoelectronic, and micro/nanofuidicdevices.Third, edge effect of NIL has been used to fabricate conduting polymernanowires with feature sizes much smaller than that of the original stamp. Thismethod involves fabrication of high-resolution mold by edge-directed capillaryforce and fabrication of high-resolution conducting polymer wires with thefabricated mold by NIL. Based on this method, which avoids using costly stampwith nanoscales, the high-resolution stamp in the second imprint was carried outwith low-cost microscale stamp. The resulting conducting-polymer nanowiresexhibit excellent sensitivity to NH3. This method may potentially be used toconstruct other organic nanoelectronic devices.