• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.999-1005
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• 2004

A new stamp fabrication technique for the soft lithography has been developed in the range of several microns by means of a nano-replication printing (nRP) process. In the nRP process, a figure or a pattern can be replicated directly from a two-tone bitmap figure with nano-scale details. A photopolymerizable resin was polymerized by the two-photon absorption which was induced by a femtosecond laser. After the polymerization of master patterns, a gold metal layer (about 30 ㎚ thickness) was deposited on the fabricated master patterns for the purpose of preventing a join between the patterns and the PDMS, then the master patterns were transferred in order to fabricate a stamp by using the PDMS (poly-dimethylsiloxane). In the transferring process, a few of gold particles, which were isolated from the master patterns, remained on the PDMS stamp. A gold selective etchant, the potassium iodine (KI) was employed to remove the needless gold particles without any damage to the PDMS stamp. Through this work, the effectiveness of the nRP process with the PDMS molding was evaluated to make the PDMS stamp with the resolution of around 200 ㎚.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.40-43
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• 2004

Stamps for microcontact processing are fabricated by casting elastomer such as PDMS on a master with a negative of the desired pattern. After curing, the PDMS stamp is peeled away from the master and exposed to a solution of ink and then dried. Transfer of the ink from the PDMS stamp to the substrate occurs during a brief contact between stamp and substrate. Generally, negative-tone masters, which are used for making positive-tone PDMS stamps, are fabricated by using photolithographic technique. The shortcomings of photolithography are a relative high-cost process and require extensive processing time and heavy capital investment to build and maintain the fabrication facilities. The goal of this study is to fabricate a negative-tone master by using Nano-indenter based patterning technique. Various sizes of V-grooves and U-groove were fabricated by using the combination of nanoscratch and HF isotropic etching technique. An achieved negative-tone structure was used as a master in the PDMS replica molding process to fabricate a positive-tone PDMS stamp.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.84-87
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• 2009

This paper describes a novel method for fabricating large area metallic stamp with high aspect ratio micro intaglio features. Micro machined brass master with pillar and larger width groove patterns were electroformed to form inverse structures on the large area metallic stamp. This enabled large area metallic stamp with fine micro high aspect ratio micro intaglio features which were small width groove patterns and quadrilateral hole patterns that cannot be fabricated by direct micro machining process. Fabricated large area metallic stamp with high aspect ratio micro intaglio features was measured and analyzed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.676-679
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• 2005

Nano imprint Lithography (NIL) is regarded as one of the next-generation lithography technologies with EUV lithography, immersion lithography, Laser interference lithography. Because a Si wafer stamp and a quartz stamp, used to imprinting usually are very expensive and easily broken, it is suggested that master stamp is duplicated by PDMS and the PDMS stamp uses to imprint .For using the PDMS stamp, a thermally curable monomer resin was used for the imprinting process to lower pressure and temperature. As a result, NIL patterns were successfully fabricated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.624-627
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• 2003

Microcontact printing (uCP) of alkanethiols on gold was the first representative of soft-lithography processes. This is an attempt to enhance the accuracy of classical to a precision comparable with optical lithography, creating a low-cost, large-area, and high-resolution patterning process. Microcontact printing relies on replication of a pattered PDMS stamp from a master to form an elastic stamp that can be inked with a SAM solution(monolayer -forming ink) using either immersion inking or contact inking. The inked PDMS stamp is then used to print a pattern that selectively protects the gold substrate during the subsequent etch.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.7 s.184
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• pp.138-145
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• 2006

A nanopatterning technique was proposed and demonstrated for low cost and mass productive process using the scanning probe lithography (SPL) and soft lithography. The nanometer scale structure is fabricated by the localized generation of oxide patterning on the H-passivated (100) silicon wafer, and soft lithography was performed to replicate of nanometer scale structures. Both height and width of the silicon oxidation is linear with the applied voltagein SPL, but the growth of width is more sensitive than that of height. The structure below 100 nm was fabricated using HF treatment. To overcome the structure height limitation, aqueous KOH orientation-dependent etching was performed on the H-passivated (100) silicon wafer. Soft lithography is also performed for the master replication process. Elastomeric stamp is fabricated by the replica molding technique with ultrasonic vibration. We showed that the elastomeric stamp with the depth of 60 nm and the width of 428 nm was acquired using the original master by SPL process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.42-42
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• 2003

• Korean Journal of Materials Research
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• v.15 no.9
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• pp.589-593
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• 2005

Nanoimprinting lithography (NIL) is known as a suitable technique for fabricating nano and micro structures of high definition. Hot embossing is one of NIL techniques and can imprint on thin films and bulk polymers. Key issues of hot embossing are time and expense needed to produce a stamp withstanding a high temperature and pressure. Fabrication of a metal stamp such as an electroplated nickel is cost intensive and time consuming. A ceramic stamp made by silicon is easy to break when the pressure is applied. In this paper, a plastic stamp using a high temperature epoxy was fabricated and tested. The plastic stamp was relatively inexpensive, rapid to produce and durable enough to withstanding multiple hot embossing cycles. The merits of low viscosity epoxy solutions were a fast degassing and a rapid filling the microstructures. The hot embossing process with plastic stamp was performed on PMMA substrates. The hot embossing was conducted at 12.6 bar, $120^{\circ}C$ and 10 minutes. An imprinted PMMA wafer was almost same value of the plastic stamp after 10 times embossing. Entire fabrication process from silicon master to plastic stamp was completed within 12 hours.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.933-934
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• 2009

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.16-21
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• 2005

Photonic crystals, periodic structure with a high refractive index contrast modulation, have recently become very interesting platform for the manipulation of light. The existence of a photonic bandgap, a frequency range in which the propagation of light is prevented in all directions, makes photonic crystal very useful in application where the spatial localization of light is required, for example waveguide, beam splitter, and cavity. However, the fabrication of 3 dimensional photonic crystals is still difficult process. A concept that has recently attracted a lot of attention is a planar photonic crystal based on a dielectric membrane, suspended in the air and perforated with two dimensional lattice of hole. The fabrication of Si master with pillar structure using hot embossing process is investigated for two dimensional, low-index-contrast photonic crystal waveguide. From our research we show that the multiple stamp copy process proved to be feasible and useful.