• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.670-673
• /
• 2003

Fabrication of three dimensional microstructures by laser-assisted chemical vapor deposition of material is investigated. To fabricate microstructures, a thin layer of deposit in desired patterns is first written using laser direct writing technique and on top of this layer a second layer is deposited to provide the third dimension normal to the surface. By depositing many layers. a three dimensional microstructure is fabricated. Optimum deposition conditions for direct writing of initial and subsequent layers with good surface quality and profile uniformity are determined. Using an arson ion laser and ethylene as the light source and reaction gas, respectively, fabrication of three-dimensional carbon microstructures is demonstrated.

• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.12
• /
• pp.136-142
• /
• 2007

Precise fabrication of three-dimensional (3D) self-standing microstructures on thin glass plates via two-photon induced polymerization (TPP) has been an important issue for innovative 3D nanodevices and microdevices. However, there are still issues remaining to be solved, such as building 3D microstructures on opaque materials via TPP and being able to implant them as functional parts onto practical systems. To settle these issues simply and effectively, we propose a contact print lithography (CPL) method using an ultraviolet (UV)-curable polymer layer. We report some of the possibilities and potential of CPL by presenting our results for transplanting 3D microstructures onto large-area substrates and also our examination of some of the effects of the process parameters on successful transplantation.

• Interaction and multiscale mechanics
• /
• v.3 no.3
• /
• pp.213-234
• /
• 2010

A multiscale method is presented for analysis of thin slab structures in which the microstructures can not be reduced to two-dimensional plane stress models and thus three dimensional treatment of microstructures is necessary. This method is based on the classical asymptotic expansion multiscale approach but with consideration of the special geometric characteristics of the slab structures. This is achieved via a special form of multiscale asymptotic expansion of displacement field. The expanded three dimensional displacement field only exhibits in-plane periodicity and the thickness dimension is in the global scale. Consequently by employing the multiscale asymptotic expansion approach the global macroscopic structural problem and the local microscopic unit cell problem are rationally set up. It is noted that the unit cell is subjected to the in-plane periodic boundary conditions as well as the traction free conditions on the out of plane surfaces of the unit cell. The variational formulation and finite element implementation of the unit cell problem are discussed in details. Thereafter the in-plane material response is systematically characterized via homogenization analysis of the proposed special unit cell problem for different microstructures and the reasoning of the present method is justified. Moreover the present multiscale analysis procedure is illustrated through a plane stress beam example.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.4
• /
• pp.303-309
• /
• 2008

Dense and fine polymer patterns often collapse, as they come into contact with each other at their protruding tips. Resist pattern collapse depends on the aspect ratio of patterns and the surface tension of rinsing materials. The pattern collapse is a very serious problem in microfabrication, because it is one of the factors which limit the device dimensions. The reasons for the pattern collapse are known as the surface tension of rinse liquid, centrifugal force and rinse liquid flow produced in the developing process. In this work, we tried to evaluate the pattern collapse of three-dimensional microstructures that were fabricated by two-photon induced photopolymerization, and showed the way how to reduce the deformation of microstructures.

• Proceedings of the IEEK Conference
• /
• 1999.11a
• /
• pp.203-207
• /
• 1999

In this paper we report new integration technology developed for three-dimensional metallic microstructures in an arbitrary shape. We have developed the two fabrication methods: Multi-Exposure and Single-Development (MESD) and Sacrificial Metallic Mold(SMM) techniques. Three-dimensional photoresist mold can be formed by the MESD method while unlimited number of structural levels can be realized by the SMM technique. Using these two techniques we have fabricated solenoid inductors and levitated spiral inductors for RF applications. We have achieved peak Q- factors over 40 in the 2-10㎓ range, the highest number among the inductors reported to date. Finally, we propose "On-Chip Passives" as a post IC process for monolithic integration of inductors, tunable capacitors, microwave switches, transmission lines, and mixers and filters toward future single-chip transceiver integration.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.157-158
• /
• 2006

A novel nanofabrication process has been developed using two-photon crosslinking (TPC) for the fabrication of three-dimensional (3D) SiCN ceramic microstructures applicable to high functional 3D devices, which can be used in harsh working environments requiring a high temperature, a resistance to chemical corrosion, as well as tribological properties. After sequential processes: TPC and pyrolysis, 3D ceramic microstructures are obtained. However, large shrinkage due to low-ceramic yield during the pyrolysis is a serious problem to be solved in the precise fabrication of 3D ceramic microstructures. In this work, silica nanoparticles were employed as a filler to reduce the amount of shrinkage. In particular, the ceramic microstructures containing 40 wt% silica nanoparticles exhibited relatively isotropic shrinkage owing to its sliding free from the substrate during pyrolysis.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.1
• /
• pp.130-137
• /
• 2008

Two-photon stereolithography (TPS) is recognized as a useful process for the fabrication of three-dimensional microstructures. Recently, the need for a two-photon curable resin with high strength increases as 3-D moicrostructures of high aspect ratio or large scale of several hundreds micrometers are required for applications of nano/micro devices in IT/BT. In this work, process parameters of TPS employing the SU-8 which is a representative two-photon curable resin with high strength have been studied for the precise fabrication of 3-D microstructures with high strength. The pre-baking and post-baking processes are studied and the parameter study of the SU-8 in TPS is conducted. Through this work, very small roughness of 12 nm and the minimum aspect ratio of ${\sim}1$ which provides a precise accumulation of layers could be obtained. Using the conditions studied in this work, some 3-D examples are fabricated.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.1
• /
• pp.46-50
• /
• 2004

The curing characteristics of a liquid photopolymer during microstereolithography and the shape accuracy of thereby fabricated microstructures were investigated experimentally. A He-Cd laser with a wavelength of 442nm and a photopolymer consisted of a commercial resin from SK chemical and a photoinitiat or were used for the experiment. By varying the laser beam power and scanning speed of the focused laser beam, minimum curing thickness of 50 ${\mu}ㅡ$ was obtained. The distortion of solidified structure due to adhesion force was measured and the optimum fabrication conditions were determined. Also, the feasibility of direct fabrication of three-dimensional microstructures by Super IH process was examined.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.10a
• /
• pp.595-596
• /
• 2009

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.8
• /
• pp.119-125
• /
• 2009

Fabrication of a three-dimensional (3D) metallic mold for multi-production of a microstructure was studied to settle the problem of long processing time in 3D microfabrication. To date, complicated 3D microstructures including 3D photonic crystals, 3D microlens array, 3D filter for microfludics, and something else were created successfully using the two-photon polymerization (TPP) which was considered as paving the way to fabricate a real 3D shape in nano/microscale. However, for those fabrications, much processing time and efforts were inevitably required. To solve this issue, a simple and effective way was proposed in this paper; 3D master patterns were prepared using TPP, and then counter-shaped Ni molds were fabricated by electroforming process. By using these molds, 3D microstructures can be reproduced with short-processing time and low-effort comparing to the conventional approach, TPP We report some parameters to fabricate a metallic mold precisely.