Papers by Author: Ki Yeon Yang

Abstract: Self-Assembled Monolayer (SAM) is a single layer of ordered molecules absorbed on a surface by chemical bonding between the molecular head group and the surface. The surface properties can be controlled by the terminal functional group of the SAM layer. In order to utilize SAM layers for device applications, SAM layer needs to be patterned as a sub-micron size. Patterning of SAM layer in sub-micron size has been done by various techniques including direct-writing by dip-pen nano lithography, selective etching with UV photons, and selective deposition of SAM layer by &-contact printing. In this study, silane based SAM layer was patterned to the sub-micron size using zero residual Nano imprint Lithography, which is regarded as next generation lithography technique due to its simplicity, high throughput and high resolution pattern transferring capability. Using zero-residual layer imprinting, 300nm~2um sized SAM patterns can successfully fabricated. In order to check the surface property of patterned SAM layer, a solution containing nano Ag particles was spin-coated on the SAM patterned substrate and nano Ag particles were selectively deposited on the substrate.

Abstract: Embossing lithography is one of the most promising technologies for mass production of nano-scale structures. To advance the industrialization of embossing lithography, fabrication of low cost, high mechanical strength embossing template is essential. Electroformed Ni template can be used as an embossing template if its poor anti-adhesive property is fixed by proper releasing layer treatment, especially, when it is used with sticky thermoset polymer. In this experiment, quartz master template with 200nm to 2um sized surface protrusions was fabricated and used to emboss the PMMA coated Si wafer. Then the embossed PMMA layer was coated with metal seed layer (Ni) and electroplating of Ni was followed to fabricate Ni template. To apply anti-stiction SAM layer, SiO2 and Si layer was coated on Ni template. With proper anti-stiction treatment of Ni template, sub-micron patterns were successfully transferred to sticky thermoset polymers such as epoxy resin using Ni template without any degradation of anti-adhesive property.

Abstract: A faithful pattern transferring onto a non-planar substrate was demonstrated by nano-imprinting technique. Uniform pressing of a flexible template onto a substrate was important for the faithful pattern transferring. Both the UV-based and thermal imprinting techniques were used to transfer patterns of 200nm sized features to the non-planar substrates such as outer wall of rod and inner surface of cylinder and it could be used for nano-devices such as lab on a chip.

Abstract: Flexible polyvinyl alcohol (PVA) templates with nano-sized patterns were fabricated by spin coating of PVA resin on silicon master wafer. Since PVA template has enough UV transparency, mechanical strength and thermal durability, it can be used as the template for UV-based and thermal nanoimprint lithography. The replicated patterns on the PVA template were transferred faithfully to the imprinted resin by imprinting lithography. As PVA template was dissolved in water, it was not necessary to deposit a releasing layer on the PVA template surface.

Abstract: In order to build a nano-device on polymer substrate, nano-size patterning must be done. However, conventional photolithography cannot be used to fabricate nano-sized patterns on polymer film due to the flexibility of polymer film and its potential interaction with developer solution and organic solvent. In this study, 100nm sized dense line and space patterns were made on flexible PET (polyethylene-terephthalate) substrate using newly developed monomer based imprinting lithography. Compared to hot embossing lithography, thermal curing imprint lithography uses monomer based imprint resin which consists of base monomer and thermal initiator. Since it is liquid phase and polymerization temperature is much lower than glass temperature of polymer, the nano-sized patterns can be transfer at much lower temperature and pressure. Hence, patterns as small as 100nm were successfully fabricated on flexible PET film substrate by monomer based thermal curing imprinting lithography at 85°C and 5atm.

Abstract: Embossing or imprint lithography is the key-technology for the mass production of nanosized structures with low cost. Currently Si or quartz template which is produced by e-beam or DUV lithography and reactive ion etching, is used. However they are very expensive and easily damaged due to their brittleness. On the other hand, Ni template has high mechanical durability and can be fabricated with low cost by electroplating. However, one of the key obstacles of Ni template is poor antistiction property, when it is used with sticky thermoset polymer. Due to its poor antistiction property, detachment of Ni template from epoxy substrate is one of the key obstacles. In this experiment, quartz template with 150nm to 1μm sized surface protrusion was fabricated and used to emboss the PMMA coated Si wafer. Then the imprinted PMMA layer was coated with metal seed layer and electroplating of Ni was followed to fabricate Ni template with 150nm to 1μm sized patterns. In order to form antistiction layer on Ni template, SAM antistiction layer was formed on SiO2 coated Ni template. As a result, nano patterns could be successfully transferred to sticky thermoset polymer using Ni template without any degradation of antistiction property.

Abstract: Embossing or imprint lithography is the key-technology for the mass production of nanosized structures with low cost. Currently Si or quartz template which is produced by e-beam or DUV lithography and reactive ion etching, is used. However they are very expensive and easily damaged due to their brittleness. On the other hand, Ni template has high mechanical durability and can be fabricated with low cost by electroplating. However, one of the key obstacles of Ni template is poor antistiction property, when it is used with sticky thermoset polymer. Due to its poor antistiction property, detachment of Ni template from epoxy substrate is one of the key obstacles. In this experiment, quartz template with 150nm to 1μm sized surface protrusion was fabricated and used to emboss the PMMA coated Si wafer. Then the imprinted PMMA layer was coated with metal seed layer and electroplating of Ni was followed to fabricate Ni template with 150nm to 1μm sized patterns. In order to form antistiction layer on Ni template, SAM antistiction layer was formed on SiO2 coated Ni template. As a result, nano patterns could be successfully transferred to sticky thermoset polymer using Ni template without any degradation of antistiction property.

Abstract: The fabrication of nano-structured materials using nanoimprint lithography has become more prevalent in recent years, due to its cost effectiveness and readiness. However, One of the biggest drawback of this technique is the fabrication of the imprinting stamp, which is expensive and difficult to fabricate. This paper describes a method of replication original Si or quartz made imprinting template into a polymer stamp which has many advantages, such as the simplicity and low cost of the fabrication process and the flexibility of the resulting stamp. Using the hot embossing method, PVC based imprint stamp with sub 100nm patterns can be fabricated. Due to its high UV transmittance, reasonable mechanical hardness and low surface energy, PVC based nanosized template can be used as a stamp for UV-NIL and sub 100nm patterns were successfully transferred by the UV-NIL process with PVC based imprint stamp.

Abstract: UV nano imprint lithography (UV NIL) that uses a monomer based UV curable monomer resin is proposed as a method of imprinting at low temperature and pressure. The fabrication of high fidelity patterns on a topographical substrate is a formidable challenge. To accomplish this, the use of bi-layer nano imprint lithography, which involves the use of an easily removable under-layer and an imprinted pattern, is proposed. We hypothesized that by etching the under layer by oxygen RIE, we might be able to build the bi-layer patterns for easy lift-off and fabricate nano-sized metal patterns through this lift-off process.