• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.1076-1079
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• 1997

A new 3D micromachining method, called Hole Area Modulation(HAM), has been introduced and experimentally confirmed its feasibility. In this method, information on the depth of machining is converted to the sizes of small holes in the mask. The machining is carried out with a simple 2D movement of the workpiece. This method can be applied for machining various kinds of microcavities in various materials. In this paper, a mathematical model for excimer laser micromachining based on HAM and also determination of the optimal laser ablation conditions(width, Hole radius, step size, path, etc.) is completed by employing using Genetic Algorithm(GA).

• Laser Solutions
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• v.6 no.2
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• pp.9-17
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• 2003

Due to the heat confinement in the shallow region of the target for a short time scale, pulsed laser annealing has received an increasing interest for the fabrication of poly-Si thin film transistors(TFTs) on glass as a low cost substrate in the flat panel displays. The formation and growth mechanisms of poly silicon(poly-Si) grains in thin films are investigated using an excimer laser crystallization system. To understand the crystallization mechanism, the grain formations are observed by FESEM photography. The optical reflectance and transmittance during the crystallization process are measured using HeNe laser optics. A two-step ELC(Excimer Laser Crystallization) process is applied to enhance the grain formation uniformity.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.6
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• pp.172-177
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• 1996

We have characterized XeCl excimer-laser-induced crystallization of thin amorphous silicon films deposited by PECVD (${\alpha}$-Si:H) and LPCVD (${\alpha}$-Si). The electrical properties, surface roughness and crystallinity of crystallized thin films have been measured. The dc conductivities, crystallinity andsurface roughness of the films increased as the laser energy density and shot density were increased. The properties of laser annealed films deposited by LPCVD were better than those of thin films deposite by PECVD. We have also found that the multiple shots with relative low energy density were more benifical to the improsvement of surface roughness than the single shot with high energy density preserving the crystallinity.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.5
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• pp.318-323
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• 2000

The planarization of rough polycrystalline diamond films synthesized by DC arc discharge plasma jet CVD (chemical vapor deposition) was attempted using KrF excimer laser pulses. The effects of laser incidence angle and reaction gases (ozone and oxygen) on etching rate of diamond were studied. The temperature change of diamond and graphite with different laser fluences was calculated by computer simulation to explain the etching behavior of diamond films. The threshold energy density from the experiment for etching of pure crystalline diamond was about $1.7J/cm^2$ and fairly matched the simulation value. Preferential etching of a particular crystallographic plane was observed through scanning electron microscopy. The etching rate of diamond with ozone was lower than that with oxygen. When the angle of incidence was $80^{\circ}$ to the diamond surface normal, the peak-to-valley surface roughness was Significantly reduced from $20{\mu}m$ to $0.5{\mu}m$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.743-746
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• 2000

The removal of contaminants of silicon wafers has been investigated by various methods. Laser cleaning is the new dry cleaning technique to replace wafer wet cleaning in the near future. A dry laser cleaning uses inert gas jet to remove contaminant particles lifted off by the action of a KrF excimer laser. A laser cleaning model is developed to simulate the cleaning process and analyze the influence of contaminant particles and experimental parameters on laser cleaning efficiency. The model demonstrates that various types of submicrometer-sized particles from the front sides of silicon wafer can be efficiently removed by laser cleaning. The laser cleaning is explained by a particle adhesion model. including van der Waals forces and hydrogen bonding, and a particle removal model involving rapid thermal expansion of the substrate due to the thermoelastic effect. In addition, the experiment of wafer laser cleaning using KrF excimer laser was conducted to remove various contaminant particles.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1999.11a
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• pp.58-63
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• 1999

In order to analyze the discharge-pumped KrF excimer laser, computer simulation code is developed. On the other hand, the electron velocity distribution in a discharge plasma, measured by the Thomson scattering method, showed the Maxwellian, while the code predicted non-Maxwellian. This disagreement was solved by introducing the electron-electron collision into the simulation code. We also developed a simulation code on the CO2 laser-heated plasma in high-pressure Ar gas, and estimated the formation process of Ar2 excimer. The code predicted the possibility of the Ar2 laser action at 126 nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.129-130
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• 2008

Polycrystalline silicon (poly-Si) Schottky barrier thin film transistors (SB-TFT) are fabricated by erbium silicided source/drain for n-type SB-TFT. High quality poly-Si film were obtained by crystallizing the amorphous Si film with excimer laser annealing (ELA) or solid phase crystallization (SPC) method. The fabricated poly-Si SB-TFTs have a large on/off current ratio with a low leakage current. Moreover, the electrical characteristics of poly-Si SB TFTs are significantly improved by the additional forming gas annealing in 2 % $H_2/N_2$, because the interface trap states at the poly-Si grain boundaries and at the gate oxide/poly-Si channel decreased.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1032-1035
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• 2009

Several different production technologies for Low-Temperature Poly-Silicon (LTPS) have been proposed over the last years. However, finally the progress in Excimer-laser-based crystallization has lead to the best cost-to-performance ratio of LTPS manufacturing for use in active-matrix-based displays. In this paper, we report on recent and significant technical advances in light sources, optical beam deliveries and beam irradiation systems targeted at enabling ultra-uniform mura-free LTPS active-matrix backplanes while simultaneously lowering production costs and increasing throughput.

• Bulletin of the Korean Chemical Society
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• v.28 no.5
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• pp.811-815
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• 2007

A series of bispyrenyl-polyether have been synthesized and investigated as a fluorescent chemosensor for metal ions. The results showed that bispyrenyl-polyether system is selective towards Al3+ ion over other ions tested. In free ligand, excited at 343 nm, it displays a strong excimer emission at around 475 nm with a weak monomer emission at 375 nm. A ratiometry of monomer (375 nm) increase and excimer (475 nm) quenching was shown only when Al3+ ion is bound to ligand, because two facing pyrene groups form a less efficient overlap of π?π stacking compared with that of free ligand.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.6
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• pp.17-23
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• 2002

A new 3D micromachining method called Hole Area Modulation(HAM), has been introduced to enhance the current micromachining technology. In this method, information on the depth of machining is converted to the sizes of small holes in the mask. The machining is carried out with a simple 2D movement of the workpiece. This method can be applied for machining various kinds of microcavities in various materials. In this paper, a machematical model for excimer laser micromachining based on HAM and also determination of optimal laser ablation conditions(width hole radius, step size, path, etc.) is performed by Genetic Algorithm(GA).