• 한국정밀공학회지
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• 제22권10호
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• pp.17-25
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• 2005

• 한국정밀공학회지
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• 제23권3호
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• pp.156-162
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• 2006

Direct fabrication of nano patterns has been studied employing a nano-stereolithography (NSL) process. The needs of nano patterning techniques have been intensively increased for diverse applications for nano/micro-devices; micro-fluidic channels, micro-molds. and other novel micro-objects. For fabrication of high-aspect-ratio (HAR) patterns, a thick spin coating of SU-8 process is generally used in the conventional photolithography, however, additional processes such as pre- and post-baking processes and expansive precise photomasks are inevitably required. In this work, direct fabrication of HAR patterns with a high spatial resolution is tried employing two-photon polymerization in the NSL process. The precision and aspect ratio of patterns can be controlled using process parameters of laser power, exposure time, and numerical aperture of objective lens. It is also feasible to control the aspect ratio of patterns by truncation amounts of patterns, and a layer-by-layer piling up technique is attempted to achieve HAR patterns. Through the fabrication of several patterns using the NSL process, the possibility of effective patterning technique fer various N/MEMS applications has been demonstrated.

• 한국정밀공학회지
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• 제27권10호
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• pp.93-99
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• 2010

A nano-stereolithography is the direct patterning process with a nanoscale resolution using twophoton absorption induced by a femtosecond laser. However, in the majority of the works, the fabrication of 3D microstructures have been done only onto transparent glass due to the use of an oil immersion objective lens for achieving a high resolution. In this work, the coaxial illumination and the auto-focusing system are proposed for the direct patterning of nano-precision patterns on an opaque substrate such as a silicon wafer and a metal substrate. Through this work, 3D polymer structures and metallic patterns are fabricated on a silicon wafer using the developed process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.163-164
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• 2006

• 대한화학회지
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• 제49권3호
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• pp.292-299
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• 2005

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1365-1368
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• 2004

A scheme to control the laser power and the exposure time was studied to fabricate precise microstructures using the nanostereolithography (nSL) process. Some recent works have shown that a three-dimensional (3D) microstructure can be fabricated by the photopolymerizing process which is induced by two-photon absorption (TPA) with a femtosecond pulse laser. TPA provides the ability to confine photochemical and physical reactions within the order of laser wavelength, so neardiffraction limit features can be produced. In the nSL process, voxels are continuously generated to form a layer and then another layer is stacked in the normal direction of a plane to construct a 3D structure. Thus, fabrication of a voxel with low aspect ratio and small diameter is one of the most important parameters for fabricating precise 3D microstructures. In this work, the mechanism of a voxel formation is studied and a scheme on the control of laser power and exposure for minimizing aspect ratio of a voxel is proposed.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권1호
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• pp.45-49
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• 2006

A nano-stereolithography (NSL) process has been developed for the fabrication of three-dimensional (3D) micro-devices with high spatital resolution of approximately 100 nm. In the NSL process, a complicated 3D structure can be created by stacking layer-by-layer, so it does not require any sacrificial layer or any supporting structure. A laminated layer was fabricated by means of solidifying liquid-state monomers using two-photon absorption (TPA) which was induced by a femtosecond laser. When the fabrication of a 3D stacked structure was finished, unsolidified liquid resins were rinsed by ethanol to develop the fabricated structures; then, the polymerized structure was only left on the glass substrate. Through this work, several 3D microstructures such as a micro-channel, shell structures, and photonic crystals were fabricated to evaluate the possibility of the developed system.