Studies Of The Novel Photorresists For Uv-Naimprint Lithography

UV nanoimprint lithography (UV-NIL) has gained increasing attention as a next-generation patterning technique that allows the fabrication of nanostructures with high resolution, and that offers a complementary alternative to traditional photolithography. Due to its facile, cost-effective, and high-throughput production processes, UV-NIL technology has been successfully used in the fabrication of electric and optical devices, such as light-emitting diodes and optical-disk storage devices, and in biological applications. NIL technology is listed in the International Technology Roadmap for Semicon-ductors for 22 nm half-pitch manufacturing. Despite the achievements in NIL technology, its progress has been limited by the availability of suitable resist materials. There are many factors will be considered, for example: the viscosity, humidity, the kinetic of the reaction and the etching resistance of the resist. To fully explore the potential of UV-curable resist and increase its versatility, it is desirable to develop new resist materials. In this thesis, we developed several types of organic-inorganic composite photoresists. Meanwihle, the relationship between the properties and the structure of the resists had been studied. Furthermore, the novel photoresists were sucessfully applied in UV-NIL, pattern transfer or the fabrication of the soft- mold.1. A novel hybrid resist for UV-NIL based on the thiol-ene photopolymerization, which is comprised of mercaptopropyl polyhedral oligomeric silsesquioxane (POSS-SH), diluted benzyl methacrylate (BMA) and crosslinker trimethylolpropane trimethacrylate (TMPT). The obtained hybrid resists possess a variety of characteristics desirable for UV-NIL, including low viscosity (6.1-24.4 cP), low bulk volumetric shrinkage (5.3%), high Young's modulus (0.9-5.2 GPa), high thermal stability and excellent dry etch resistance. Based on these performances, optimized component were evaluated as UV-NIL resist. The resultant pattern exhibited the high resolution pattern with feature sizes in the range of 100 nm to several microns. The double-layer resist approach is used for pattern transfer into silicon substrates. Due to excellent oxygen etch resistance of the etch barrier material, the final height of the transfer pattern is about 3 times more than that of the original NIL pattern.2. A novel fluorinated hybrid resist as soft mold for NIL based on the thiol-ene photopolymerization was precisely designed and synthesized, which is comprised of fluorinated mercaptopropyl polyhedral oligomeric silsesquioxane (POSS-F-SH), diluted crosslinker 2,2,3,3,4,4,5,5-octafluoro-1,6-hexyl diacrylate (DCFA4). The obtained fluorinated hybrid resists possess a variety of characteristics desirable for UV-NIL, including low viscosity (16-239 cP), low bulk volumetric shrinkage (4.8-7.5%) and a good resistance to oxygen inhibition. The cross-linked hybrid resins exhibited high transparency to UV light and resistance to organic solvents. As soft mold, the excellent mechanical property (Young's modulus 0.31-1.56 GPa) and low surface energy (14-20.4 mJ/m-2) of the fluorinated polymers provided a clean mold release without fracture or deformation of the embossed structures. The thermally stability (Td >300 C) render them capable of being used for both UV and thermal NIL duplication processes. The resultant soft mold exhibited the high resolution patterning capacity with feature sizes in the range of 200 nm to several microns. After repeating 10 imprinting cycles at relatively high temperature and pressure, no detectable crack or contamination of the replica surface was observed. The economic efficiency of the mold fabrication as well as the high durability and excellent releasing properties could be quite valuable to NIL for high-throughput fabrication of nano-devices. 3. A novel hybrid resist for UV-NIL was precisely designed, and the radical-mediated thiol-yne step-growth photopolymerizations are utilized to form highly cross-linked polymer networks. The resist is comprised of mercaptopropyl and Octyl group bifunctional polyhedral oligomeric silsesquioxane (POSS-SH-OA), diluted crosslinker difunctional alkyne. The obtained hybrid resists possess numerous desirable characteristics for UV-NIL, such as great coatability, high thermal stability, hydrophobicity (water contact angle > 90 ), low bulk volumetric shrinkage (0.8~4.8%), and excellent dry etch resistance. In particular, the process of thiol-yne system allows the resists to be solidi ed within seconds under UV exposure at room temperature, Furthermore, due to excellent oxygen etch resistance of the etch barrier material, the final height of the transfer pattern is about 3 times more than that of the original NIL pattern.4. We designed a novel photo-reversible resist for UV-NIL which is comprised of a photo-reversible cross-linker (2-[(4-methyl-2-oxo-2h-1-benzo- pyran-7-yl)oxy] ethyl ester, AHEMC). Under exposure of 365 nm UV-light, this photo-reversible resist can form crosslinked network via radical polymerization of acrylate groups and photodimerization of coumarin moieties. The formed polymer networks containing coumarin dimer moieties could be degraded via illumination of point light source (254 nm). The reversibility of crosslinked system was helpful to refresh mold easily and release the adhered curing resist at room temperature.