• Korean Journal of Optics and Photonics
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• v.30 no.6
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• pp.219-225
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• 2019

In an infrared optical system, using a cooled detector generates a phenomenon called a narcissus, in which the focal-plane array cooled to very low temperatures is reflected at the lens surface and detected. The narcissus can be removed by non-uniformity correction of the detector pixel, so narcissus is generally ignored in infrared optics. However, non-uniformity correction reduces the sensitivity of the system. Also, as the housing temperature varies due to an environmental temperature change, or a lens is moved for focusing or athermalization purposes, a narcissus may occur even after non-uniformity correction. To minimize such a narcissus, the amount of the effect must be controlled in the lens-design stage. In this paper we designed a midinfrared optical system and analyzed the narcissus by setting the lens surface reflectance to 1%. In addition, the design was divided into stages of an initial design, an improved design, and a minimum design, and the narcissus was improved to about 56% of that in the initial design.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2154-2159
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• 2007

The potential of using a double-faced wall stagnation flow burner in mass production of carbon nanotubes was evaluated experimentally and computationally. With nitrogen-diluted premixed ethylene-air flames established on the Nickel-coated stainless steel double-faced wall, the propensities of carbon nanotube formation were experimentally determined using SEM and FE-TEM images and Raman spectroscopy, while the flame structure was computationally predicted using a 3-dimensional CFD code with a reduced reaction mechanism. The uniformity and yields of synthesized carbon nanotubes were evaluated in terms of the flame stretch rates. Results show substantial increase of area on the wall surface where uniform carbon nanotubes are synthesized with using the double-faced wall stagnation flow burner due to enhanced uniformity of temperature distribution along the wall surface and support the potential of using a double-faced wall stagnation flow burner in mass production of carbon nanotubes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.3
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• pp.177-181
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• 2018

We prepared ZnS thin films via chemical bath deposition (CBD) in an aqueous solution of ammonia ($NH_3$) and hydrazine ($N_2H_4$). The composition ratio of hydrazine used was 0%, 17%, 22%, 29%, or 50%. We investigated the effects of hydrazine and ammonia on the growth, and the structural and optical properties of ZnS in terms of surface uniformity, voids, and grain size. We found that during the growth of ZnS films, hydrazine was very effective for improving the surface morphology and layer uniformity with fast layer formation, while it had no effect on the bandgap energy, $E_g$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.9
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• pp.798-802
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• 2005

The plating shape in the opening of photoresist becomes gradated shape in the fountain plating system, because bubbles from the wafer surface are difficult to escape from the deep openings, vias. In this paper, the bubble flow from the wafer surface during plating process was studied and we designed the tilted electrode ring to get uniform bump height on all over the wafer and evaluated the film uniformity by SEM and $\alpha-step$. In a-step measurement, film uniformities in the fountain plating system and the tilted electrode ring contact system were $\pm16.6\%,\;\pm4\%$ respectively.

• Journal of the Korean institute of surface engineering
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• v.47 no.1
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• pp.20-24
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• 2014

Joule heat is generated by applying an electric filed to a conductive layer located beneath or above the amorphous silicon film, and is used to raise the temperature of the silicon film to crystallization temperature. An electric field was applied to an indium tin oxide (ITO) conductive layer to induce Joule heating in order to carry out the crystallization of amorphous silicon. Polycrystalline silicon was produced within the range of a millisecond. To investigate the kinetics of Joule-heating induced crystallization (JIC) solid phase crystallization was conducted using amorphous silicon films deposited by plasma enhanced chemical vapor deposition and using tube furnace in nitrogen ambient. Microscopic and macroscopic uniformity of crystallinity of JIC poly-Si was measured to have better uniformity compared to that of poly-Si produced by other methods such as metal induced crystallization and Excimer laser crystallization.

• Journal of the Korean institute of surface engineering
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• v.32 no.4
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• pp.513-520
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• 1999

In this study, we investigated the effects of variously configured magnets on the characteristics of the plasmas to enhance plasma uniformity and density of an inductively coupled plasma source. As the magnets, Helmholtz type axial electromagnets and various multi-dipole magnets types around the chamber wall were used. To characterize the plasma as a function of the combination of the magnets and magnetic field strengths, ion density, electron temperature, and plasma potential were measured using an electrostatic probe along the chamber diameter for Ar plasmas. The measured maximum ion densities were $8$\times$10^{ 11}$$cm^{-3}$ with 600W inductive power and at 5mTorr of operational pressure and the uniformity of ion density was less than 5.9% at 2mTorr of operational pressure. The combination of an optimized multi-dipole magnet type and an axial electromagnet showed the lowest electron temperature (3eV) and plasma potential ($34V{p}$ )

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.2
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• pp.156-161
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• 2004

We investigated the effects of oxidizer additive on the performance of Cu-CMP process using commonly used tungsten slurry. In order to compare the removal rate and non-uniformity as a function of oxidizer contents, we used alumina-based tungsten slurry and copper blanket wafers deposited by DC sputtering method. According to the CMP removal rates and particle size distribution, and the microstructures of surface layer by SEM image as a function or oxidizer contents were greatly influenced by the slurry chemical composition of oxidizers. The difference in removal rate and roughness of copper surface are believed to cause by modification in the mechanical behavior of $Al_2$O$_3$abrasive particles in CMP slurry.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2006.10a
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• pp.2-3
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• 2006

본 논문에서는 신경망 모델링을 통하여 HDP-CVD를 이용한 실리콘 산화막 형성에 영향을 주는 다섯 가지 공정 장비 변수와 그에 따른 두 가지 출력 파라미터 Deposition rate과 Uniformity와의 관계를 동시에 고려한 특성결과를 분석하고， 최적의 recipe를 Genetic Algorithm을 통해 제시하였다. 실험계획법을 사용하여， 필요한 실험의 횟수를 최소화 하였으며 그 실험결과를 신경망 모델링을 통하여 입력변수와 출력파라미터의 관계를 3차원의 반응표면 곡선으로 분석하였다. 이 과정을 통해 Deposition rate과 Uniformity을 동시에 고려한 두 출력파라미터를 만족하는 최적의 입력변수 값들을 제시하였다.

• Journal of the Korean institute of surface engineering
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• v.43 no.3
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• pp.154-158
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• 2010

Numerical analysis is done to investigate the effects of pulse bias on the plasma processing characteristics like ion doping and ion nitriding by using fluid dynamic code with a 2D axi-symmetric model. For 10 mTorr of Ar plasma, -1 kV of pulse bias was simulated. Maximum sheath thickness was around 20 mm based on the electric potential profile. The peak electron temperature was about 20 eV, but did not affect the averaged plasma characteristics of the whole chamber. Maximum ion current density incident on the substrate was 200 $A/m^2$ at the center, but was decreased down to 1/10th at radius 100 mm, giving poor radial uniformity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.134-135
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• 2007

Growth of cubic SiC has been carried out on oxided Si substrate using atmospheric pressure chemical vapor deposition (APCVD). Hexamethyldisilane (HMDS) was used as the single precursor and nonflammable mixture of Ar and $H_2$ was used as carrier gas. Epitaxial growth had performed depositions under the various $H_2$ conditions which were adjusted from 0 to 100 seem. The effects of $H_2$ was characterized by surface roughness, thickness uniformity, films quality and elastic modulus. Thickness uniformity and films quality were performed by SEM. Surface roughness and elastic modulus were investigated by AFM and Nano-indentor, respectively. According to the $H_2$ flow rate, Poly 3C-SiC thin film quality was improved not only physical but also mechanical properties.