• Journal of the Korean Society for Precision Engineering
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• v.26 no.6
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• pp.36-40
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• 2009

Development of maskless lithography techniques can provide a potential solution for the photomask cost issue. Furthermore, it could open a market for small scale manufacturing applications. Since femtosecond lasers have been found suitable for processing of a wide range of materials with sub-micrometer resolution, it is attractive to use this technique for maskless lithography. As a femtosecond laser has recently been developed, both of high power and high photon density are easily obtained. The high photon density results in photopolymerization of photoresist whose absorption spectrum is shorter than that of the femtosecond laser. The maskless lithography using the two-photon absorption (TPA) makes micro structures. In this paper, we present a femtosecond laser direct write lithography for submicron PR patterning, which show great potential for future application.

• Laser Solutions
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• v.3 no.3
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• pp.31-37
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• 2000

In this paper, the possibilities of the laser overlap spot welding were studied to utilize the advantageous properties of amorphous metal foils. In order to estimate the usage of amorphous metals foils as structural members, the tensile shear strength and the fracture features were investigated. Although the crystalline zone on the surface was formed, it was not the direct cause of the fracture of the weld. The fracture of the weld resulted from the geometry discontinuity between the workpiece and the protrusion zone, which was formed during the weld process. The vein pattern - the typical feature of the fracture of the amorphous metal - was formed on the fracture surface. The tensile shear stress was reached to 1200 N/㎟ (2-foils overlap welding) and 900 N/㎟ (10-foils overlap welding), whereas the tensile strength of the workpiece was 1500-2000 N/㎟.

• Electronics and Telecommunications Trends
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• v.36 no.3
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• pp.23-33
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• 2021

Two main technologies of III-V/Si laser diode for optical communication, direct epitaxial growth, and wafer bonding were studied. Until now, the wafer bonding has been vigorously studied and seems promising for the ideal III-V/Si laser. However, the wafer bonding process is still complicated and has a limit of mass production. The development of a concise and innovative integration method for silicon photonics is urgent. In the future, the demand for high-speed data processing and energy saving, as well as ultra-high density integration, will increase. Therefore, the study for the hetero-junction, which is that the III-V compound semiconductor is directly grown on Si semiconductor can overcome the current limitations and may be the goal for the ideal III-V/Si laser diode.

• Laser Solutions
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• v.12 no.1
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• pp.7-13
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• 2009

Engineering ceramics as sapphire are widely used in industry owing to their superior mechanical and corrosion properties. However, micromachining of sapphire is a considerable challenge due to its transparency. Recently, direct ablation of sapphire has been demonstrated with a visible laser pulse at sufficiently high laser intensity. In this work, the theoretical model for pulsed laser ablation of sapphire is suggested and numerical analysis is carried out using the model. Sapphire ablation begins with plasma generation by the laser interaction with surface defects, impurities and contaminations in the initial stage of machining. Subsequent absorption of the visible laser beam can be explained by three mechanisms: metalization of sapphire surface due to the EUV radiation from the hot plasma, increments of surface roughness and temperature-dependent absorption coefficient. Comparison of the computation results with experimental observation indicates that the proposed model of sapphire is reasonable.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.5
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• pp.396-401
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• 1999

In this study, $Ar^+$ ion laser etching process of single/poly-crystalline Si with $CCl_2F_2$ gas is investigated for MEMS applications. In general, laser direct etching process is useful in microelectronic process, fabrication of micro sensors and actuators, rapid prototyping, and complementary processing because of the advantages of 3D micromachining, local etching/deposition process, and maskless process with high resolution. In this study, a pyrolytic method, in which $CCl_2F_2$ gasetches molten Si by the focused laser, was used. In order to analyze the temperature profile of Si by the focused laser, the 3D heat conduction equation was analytically solved. In order to investigate the process parameters dependence of etching characteristics, laser power, $CCl_2F_2$ gas pressure, and scanning speed were varied and the experimental results were observed by SEM. The aspect ratio was measured in multiple scanning and the simple 3D structure was fabricated. In addition, the etching characteristics of $6\mum$ thick poly-crystalline Si on the insulator was investigated to obtain flat bottom and vertical side wall for MEMS applications.

• Laser Solutions
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• v.17 no.3
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• pp.19-23
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• 2014

To directly engrave circuit-line patterns as wide as $6{\mu}m$ in a buildup film to be used as an IC substrate, we applied a projection ablation technique in which an 8 inch dielectric ($ZrO_2/SiO_2$) mask, a DPSS 355nm laser instead of an excimer laser, a ${\pi}$-shaper and a galvo scanner are used. With the ${\pi}$-shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam. The galvo scanner before the $f-{\theta}$ lens moves the flat-top beam ($115{\mu}m{\times}105{\mu}m$) across the 8 inch dielectric mask whose patterned area is $120mm{\times}120mm$. Based on the results of the previous research by the authors, the projection ratio was set at 3:1. Experiments showed that the average width and depth of the engraved patterns are $5.41{\mu}m$ and $7.30{\mu}m$, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.7 s.172
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• pp.27-37
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• 2005

Direct writing technology on the silicon wafer surface is used to reduce the size of the chip as the miniature trend in electronic circuit. In order to improve the productivity and efficiency, the real time quality estimation is very important in each semiconductor process. In laser marking, marking quality is determined by readability which is dependant on the contrast of surface, the line width, and the melting depth. Many researchers have tried to find theoretical and numerical estimation models fur groove geometry. However, these models are limited to be applied to the real system. In this study, the estimation system for the line width during the laser marking was proposed by process monitoring method. The light intensity emitted by plasma which is produced when irradiating the laser to the silicon wafer was measured using the optical sensor. Because the laser marking is too fast to measure with external sensor, we build up the coaxial monitoring system. Analysis for the correlation between the acquired signals and the line width according to the change of laser power was carried out. Also, we developed the models enabling the estimation of line width of the laser marking through the statistical regression models and may see that their estimating performances were excellent.

• Transactions of Materials Processing
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• v.13 no.3
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• pp.216-224
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• 2004

In this study, we have developed a new UV$({\lambda}=355nm)$ laser micromachining technology by direct ablation method without masks. This technology allows that 3D micro parts can be fabricated rapidly and efficiently with a low price. And it has a benefit of reducing fabricating process simply. Due to micro parts' fabrication, such technologies need the control of XYZ stages with high precision, the design of optical devices to maintain micron spot sizes of laser beam and the control technology of laser focus. The developed laser manufacturing process for laser micromachining is that, after extracting coordinates of shape data from CAD model data, a beam path considering manufacturing features of laser beam is created by using genetic algorithm. This generated manufacturing process is sent to stage controller. In order to improve the surface quality of micro parts, we have carried out experiments on iteration manufacturing and beam step-over by using a minimum focus size. Moreover, we have fabricated a micro-channel through the developed laser micromachining technology and verified it through the results.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.4
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• pp.261-268
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• 1999

Laser-induced thermochemical etching has been recognized as a new powerful method for processing a variety of materials, including metals, semiconductors, ceramics, insulators and polymers. This study presents characteristics of direct etching for Si substrate using focused argon ion laser beam in aqueous KOH and $CCl_2F_2$ gas. In order to determine process conditions, we first theoretically investigated the temperature characteristics induced by a CW laser beam with a gaussian intensity distribution on a silicon surface. Major process parameters are laser beam power, beam scan speed and reaction material. We have achieved a very high etch rate up to $434.7\mum/sec$ and a high aspect ratio of about 6. Potential applications of this laser beam etching include prototyping of micro-structures of MEMS(micro electro mechanical systems), repair of devices, and isolation of opto-electric devices.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.4
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• pp.1-9
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• 2009

It establishes the nonlinear optics material recently on solid-state laser output side and from the infrared ray until is early has in the ultraviolet rays and the wavelength of broadband there makes be a possibility of getting the laser light which and in processing and measuring field it is widely used. Consequently, it used the pulse reiteration law from origination and nine as the fundamental wave direct plan it produced. intense it affixed the nonlinear optics material (KTP) in pulsed light and it got the green light. When inflicting a same energy in respectively reiteration mesh, intense interrelation of pulse light output and green light output between. It analyzed the conversion ratio which it follows in the mesh.