부인과 악성종양의 진단에 있어 Fine-Needle Aspiration Cytology의 효용

김현세,손일표,김은성,심재욱,한원희,박종택,김희숙,홍성란 대한산부인과학회 1989 Obstetrics & Gynecology Science Vol.32 No.5

유한요소 해석을 이용한 액화수소 펌프 누설량 예측

김현세,함영복 한국수소및신에너지학회 2023 한국수소 및 신에너지학회논문집 Vol.34 No.3

Until recently, ships, automobiles, and drones using hydrogen energy are being actively researched. In addition, stations and facilities for hydrogen supply are being developed widely. Among them, a hydrogen pump is necessary for compressing it and transfer to other stations. The liquid hydrogen pump is operated at very high pressure up to 90 MPa. In our research, a reciprocating plunger pump is studied. Especially, a leakage in a liquid hydrogen pump is predicted using a finite element method. As a result, it was found that leak mass flow rates changed from 0.09 to 2.20 kg/h, when the gaps were given from 2 to 6 μm. Thus pump efficiencies were calculated from 99.9 to 97.9%, when the gaps changed from 2 to 6 μm. These results are useful for the design of the liquid hydrogen pump.

A Quartz-bar Megasonic System for Nano-pattern Cleaning

김현세,이양래,임의수 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.

A quartz-bar megasonic system for cleaning nano-particles with uniform acoustic pressures, was designed and manufactured. The impedance graph of the piezoelectric actuator used in the system was predicted using a finite element method (FEM); this gives the anti-resonance frequency of the piezoelectric actuator alone as 987 kHz, which is the same as the experimentally measured value. The impedance graph of the megasonic system was also analyzed. The predicted anti-resonance frequency of the system was 987 kHz, which agreed well with the measured frequency of 983 kHz. The acoustic pressure distributions of the developed system were examined using an acoustic pressure measurement system. The measured average acoustic pressure and its uniformity were compared with a commercially available product in terms of evaluating the system performance. The average acoustic pressure of the bar-type megasonic system was increased by 89%, while standard deviations of the bar-type megasonic system were decreased by 20%. This implies that the developed bar-type megasonic has an improved capability of particle removal efficiency (PRE) as well as better uniformity of the acoustic pressures.

Design of a Thermoelectric Layer for a Micro Power Generator

김현세,이양래,이공훈 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.

In this article, an n-type polycrystalline silicon (poly-Si) layer for a micro thermoelectric generator (TEG) was designed using Taguchi methods. Design parameters for this experiment were thicknesses of oxide and poly-Si films, and fabrication conditions in the boron ion-implantation process. Based on an L9 (34) orthogonal array, nine different poly-Si testpieces were fabricated on 525 μm-thick Si substrates. Oxide and poly-Si films were deposited using the low pressure chemical vapor deposition (LPCVD) method on cleaned wafers. Subsequently, phosphorous ions were implanted in the poly-Si layers with different process conditions. The crystalline structures of the fabricated specimens were observed using X-ray diffraction (XRD). The XRD analysis results demonstrated that each specimen was well crystallized with (2 2 0) orientation. The Seebeck coefficient and electrical conductivity including the Hall coefficient, Hall mobility, and carrier concentration were measured. The power factor of each testpiece was calculated. Through analysis, the power factor of an optimized poly-Si layer was predicted to be 798 μWm-1K-2. The optimized design parameters were 0.2 μm-thick oxide films, 1.5 μm-thick poly-Si films, 130 keV energy of the ion implantation process, and 1015 cm-2 dopant dose of the phosphorous ions.

Finite Element Analysis and Fabrication of a 3 MHz Megasonic System for Semiconductor Cleaning

김현세,임의수,이양래 한국생산제조학회 2022 한국생산제조학회지 Vol.31 No.3

Megasonic cleaning has been used to clean contaminants from wafer surfaces in semiconductor production. This research developed a 3 MHz megasonic waveguide for cleaning processes in semiconductor industries. Firstly, a 1 MHz type was fabricated in aluminum (Al) and quartz, consisting of a lead zirconate titanate (PZT) actuator and a waveguide. A 3 MHz quartz waveguide was also fabricated based on the fabricated results, and its performance was tested. In the design process, finite element analysis was performed. As a result, the predicted value was 2.997 MHz, which agreed with the measured value of 2.995 MHz with a 0.1% error. Lastly, a particle removal efficiency (PRE) test was performed, and the results showed that 93.1% PRE was achieved at 8W power. Considering the acoustic pressure and the cleaning test results, the 3 MHz megasonic may help the removal of contaminants from wafer surfaces effectively.

마이크로 발전기의 열전박막 설계

김현세,이양래,이공훈 대한기계학회 2007 環境管理學會誌 Vol.2007 No.5

In this research, a polycrystalline silicon (poly-Si) film layer for micro thermoelectric generator (TEG) was fabricated. The fabrication process of the thermoelectric poly-Si film layer is explained. The P-type and N-type poly-Si films were fabricated on a tetra ethoxy silane (TEOS) layer with a supporting Si wafer. Seebeck coefficient and electrical conductivity were measured, including the transport properties such as the hall coefficient, hall mobility and carrier concentration. The design parameters for a rapid thermal process (RTP) were decided based on the experimental results. The measured power factors of the P-type and N-type were <TEX>$21.2\;{\mu}Wm^{-1}K^{-2}$</TEX> and <TEX>$26.7\;{\mu}Wm^{-1}K^{-2}$</TEX>, respectively.

Development of a plate-type megasonic with cooling pins for sliced ingot cleaning

김현세,임의수 한국반도체디스플레이기술학회 2023 반도체디스플레이기술학회지 Vol.22 No.3

In this article, a plate-type megasonic cleaning system with cooling pins is proposed for the sliced ingot, which is a raw material of silicon (Si) wafers. The megasonic system is operated with a lead zirconate titanate (PZT) actuator, which has high electric resistance, thus when it is being operated, it dissipates much heat. So this article proposes a megasonic system with cooling pins. In the design process, finite element analysis was performed and the results were used for the design of the waveguide. The frequency with the maximum impedance value was 998 kHz, which agreed well with the measured value of 997 kHz with 0.1 % error. Based on the results, the 1 MHz waveguide was fabricated. Acoustic pressures were measured, and analyzed. Finally, cleaning tests were performed, and 90 % particle removal efficiency (PRE) was achieved over 10 W power. These results imply that the developed 1 MHz megasonic will effectively clean sliced ingot wafer surfaces.

Fabrication and Performance Tests of an Ultrasonic Cleaning System for Solar-cell Wafers

김현세,임의수,이양래,박종권 한국생산제조학회 2019 한국생산제조학회지 Vol.28 No.4

In this study, a midsonic cleaning system for solar-cell wafers with a frequency of 750 kHz was designed and fabricated. Finite element analysis was used to design the system. The obtained peak admittance value was 750.0 kHz. Reflecting the analysis results, the system was fabricated and its admittance characteristic was measured. The measured data showed 753.1 kHz, a value that was consistent with the finite element method (FEM) result with 0.4% error. The acoustic pressure test was performed and the resulting pressures were found to range from 283% to 328%, with a standard deviations range from 36.8% to 39.2%. Then, the wafer damage test was performed, and no damage was observed. Finally, the particle-cleaning test was performed; when we applied 1100 W, 99.8% of particles were removed. These results indicate that the developed midsonic bath has the capability of cleaning effectively without inflicting wafer breakage.

Vibration characteristics of an ultrasonic waveguide for cooling

김현세,임의수 한국음향학회 2020 韓國音響學會誌 Vol.39 No.6

Ultrasound has been widely used in various industrial fields. One of challenging application areas is cooling microelectronics. Ultrasonic cooling systems can work with air, argon (Ar) and nitrogen (N2) instead of conventional refrigerant such as freon gas, which can cause global warming. Furthermore, ultrasonic systems do not have moving parts, thus high durability can be obtained. So it is necessary to develop ultrasonic cooling systems due to environmental issues and durability points. In this paper, the design and fabrication processes are explained. When designing the system, a feasibility test was performed with a prototype cooler. Based on the result, finite element analysis with ANSYS software was performed. The predicted anti-resonance frequency for a piezoelectric actuator was 34.8 kHz, which was in good agreement with the experimental result of 34.6 kHz with 0.6% error. In addition, the predicted anti-resonance frequency for the ultrasonic waveguide was 39.4 kHz, which also agreed well with the experimental value of 39.8 kHz with 1.0% error. Based on these results, the developed ultrasonic waveguide might be applicable in microchip cooling.

Bare Wafer 세정용 1 MHz 급 메가소닉 개발

김현세,임의수 한국반도체디스플레이기술학회 2023 반도체디스플레이기술학회지 Vol.22 No.2

In semiconductor manufacturing processes, a cleaning process is important that can remove sub-micron particles. Conventional wet cleaning methods using chemical have limits in removing nano-particles. Thus, physical forces of a mechanical vibration up to 1 MHz frequency, was tried to aid in detaching them from the substrates. In this article, we developed a 1 MHz quartz megasonic for a bare wafer cleaning using finite element analysis. At first, a 1 MHz megasonic prototype was manufactured. Using the results, a main product which can improve a particle removal performance, was analyzed and designed. The maximum impedance frequency was 992 kHz, which agreed well with the experimental value of 986 kHz (0.6% error). Acoustic pressure distributions were measured, and the result showed that maximum / average was 400.0~432.4%, and standard deviation / average was 46.4~47.3%. Finally, sub-micron particles were deposited and cleaned for the assessment of the system performance. As a result, the particle removal efficiency (PRE) was proved to be 92% with 11 W power. Reflecting these results, the developed product might be used in the semiconductor cleaning process.