• JSTS:Journal of Semiconductor Technology and Science
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• 제1권1호
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• pp.84-93
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• 2001

An electromagnetic micro x-y stage for probe-based data storage (PDS) has been fabricated. The x-y stage consists of a silicon body inside which planar copper coils are embedded, a glass substrate bonded to the silicon body, and eight permanent magnets. The dimensions of flexures and copper coils were determined to yield $100{\;}\mu\textrm{m}$ in x and y directions under 50 mA of supplied current and to have 440 Hz of natural frequency. For the application to PDS devices, electromagnetic stage should have flat top surface for the prevention of its interference with multi-probe array, and have coils with low resistance for low power consumption. In order to satisfy these design criteria, conducting planar copper coils have been electroplated within silicon trenches which have high aspect ratio ($5{\;}\mu\textrm{m}$in width and $30{\;}\mu\textrm{m}$in depth). Silicon flexures with a height of $250{\;}\mu\textrm{m}$ were fabricated by using inductively coupled plasma reactive ion etching (ICP-RIE). The characteristics of a fabricated electromagnetic stage were measured by using laser doppler vibrometer (LDV) and dynamic signal analyzer (DSA). The DC gain was $0.16{\;}\mu\textrm{m}/mA$ and the maximum displacement was $42{\;}\mu\textrm{m}$ at a current of 180 mA. The measured natural frequency of the lowest mode was 325 Hz. Compared with the designed values, the lower natural frequency and DC gain of the fabricated device are due to the reverse-tapered ICP-RIE process and the incomplete assembly of the upper-sided permanent magnets for LDV measurements.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권4호
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• pp.239-247
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• 2001

The Fluorescence-Activated Cell Sorter (FACS) is a well-established instrument used for identifying, enumerating, classifying and sorting cells by their physical and optical characteristics. For a miniaturized FACS device, a disposable plastic microchip has been developed which has a hydrodynamic focusing chamber using soft lithography. As the characteristics of the spatially confined sample stream have an effect on sample throughput, detection efficiency, and the accuracy of cell sorting, systematic fluid dynamic studies are required. Flow visualization is conducted with a laser scanning confocal microscopy (LSCM), and three-dimensional flow structure of the focused sample stream is reconstructed from 2D slices acquired at $1\mutextrm{m}$ intervals in depth. It was observed that the flow structure in the focusing chamber is skewed by unsymmetrical velocity profile arising from trapezoidal cross section of the microchannel. For a quantitative analysis of a microscopic flow structure, Confocal Micro-PIV system has been developed to evaluate the accelerated flow field in the focusing chamber. This study proposes a method which defines the depth of the measurement volume using a detection pinhole. The trajectories of red blood cells (RBCs) and their interactions with surrounding flow field in the squeezed sample stream are evaluated to find optimal shape of the focusing chamber and fluid manipulation scheme for stable cell transporting, efficient detection, and sorting

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.331-331
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• 2009

Hafnium oxide ($HfO_2$) attracted by one of the potential candidates for the replacement of si-based oxides. For applications of the high-k gate dielectric material, high thermodynamic stability and low interface-trap density are required. Furthermore, the amorphous film structure would be more effective to reduce the leakage current. To search the gate oxide materials, metal-insulator-metal (MIM) capacitors was fabricated by pulsed laser deposition (PLD) on indium tin oxide (ITO) coated glass with different oxygen pressures (30 and 50 mTorr) at room temperature, and they were deposited by Au/Ti metal as the top electrode patterned by conventional photolithography with an area of $3.14\times10^{-4}\;cm^2$. The results of XRD patterns indicate that all films have amorphous phase. Field emission scanning electron microscopy (FE-SEM) images show that the thickness of the $HfO_2$ films is typical 50 nm, and the grain size of the $HfO_2$ films increases as the oxygen pressure increases. The capacitance and leakage current of films were measured by a Agilent 4284A LCR meter and Keithley 4200 semiconductor parameter analyzer, respectively. Capacitance-voltage characteristics show that the capacitance at 1 MHz are 150 and 58 nF, and leakage current density of films indicate $7.8\times10^{-4}$ and $1.6\times10^{-3}\;A/cm^2$ grown at 30 and 50 mTorr, respectively. The optical properties of the $HfO_2$ films were demonstrated by UV-VIS spectrophotometer (Scinco, S-3100) having the wavelength from 190 to 900 nm. Because films show high transmittance (around 85 %), they are suitable as transparent devices.

• 한국정밀공학회지
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• 제19권8호
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• pp.180-186
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• 2002

Hot Plate is the major unit that it used to remove damp of wafer surface, to strength adhesion of photoresist (PR) and to bake coated PR in FAB process of semiconductor. The badness of Hot Plate (HP) has directly influence upon the performance of wafer, it is necessary to guarantee the performance of HP. In this study, a reliability evaluation system has been designed and developed, which is to measure and to estimate thermal uniformity and flatness of HP in range of temperature 0~$250^\circC$. This system has included the techniques which measures and analyzes thermal uniformity using infrared thermal vision, and which compensates measuring error of flatness using laser displacement sensor For measuring flatness, a measurement stage of 3 axes are developed which adapts the precision encoder. The allowable error of this system in respect of thermal uniformity is less $than\pm0.1^\circC$ and in respect of flatness is less $than\pm$1mm . It is expected that the developed system can measure from $\Phi200mm\;(wafer 8＂)\;to\;\Phi300mm$ (wafer 12＂) and also can be used in performance test of the Cool Plate and industrial heater, etc.

• 한국항행학회논문지
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• 제10권1호
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• pp.13-19
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• 2006

본 논문에서는 FCC의 방사 스펙트럼 제한 규정에 따라 5 GHz-WLAN 주파수 대역을 억제한 DS-UWB 가우시안 임펄스 생성기를 제안하고, 이를 실험적으로 구현하였다. 단극 구형파를 가우시안 임펄스로 변환하기 위해 SRD를 이용한 첫 번째 임펄스 생성기와 반도체 레이저의 이득 스위칭을 이용한 두 번째 임펄스 생성기로 구성된 2단 구조의 임펄스 생성기를 사용하였다. 출력된 가우시안 임펄스의 폭은 약 180 psec로 매우 짧다. 또한 WLAN 주파수 대역을 제거하기 위해 4단 링 공진기 구조의 고차 미분 가우시안 필터를 설계 및 제작하여 최종적으로 WLAN 신호 대역은 약 25 dB의 억제 효과를 갖는 DS-UWB 신호의 발생기를 실험적으로 구현하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.34.2-34.2
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• 2011

The demand for Ru has been increasing in the electronic, chemical and semiconductor industry. Chemical mechanical planarization (CMP) is one of the fabrication processes for electrode formation and barrier layer removal. The abrasive particles can be easily contaminated on the top surface during the CMP process. This can induce adverse effects on subsequent patterning and film deposition processes. In this study, a post Ru CMP cleaning solution was formulated by using sodium periodate as an etchant and citric acid to modify the zeta potential of alumina particles and Ru surfaces. Ru film (150 nm thickness) was deposited on tetraethylorthosilicate (TEOS) films by the atomic layer deposition method. Ru wafers were cut into $2.0{\times}2.0$ cm pieces for the surface analysis and used for estimating PRE. A laser zeta potential analyzer (LEZA-600, Otsuka Electronics Co., Japan) was used to obtain the zeta potentials of alumina particles and the Ru surface. A contact angle analyzer (Phoenix 300, SEO, Korea) was used to measure the contact angle of the Ru surface. The adhesion force between an alumina particle and Ru wafer surface was measured by an atomic force microscope (AFM, XE-100, Park Systems, Korea). In a solution with citric acid, the zeta potential of the alumina surface was changed to a negative value due to the adsorption of negative citrate ions. However, the hydrous Ru oxide, which has positive surface charge, could be formed on Ru surface in citric acid solution at pH 6 and 8. At pH 6 and 8, relatively low particle removal efficiency was observed in citric acid solution due to the attractive force between the Ru surface and particles. At pH 10, the lowest adhesion force and highest cleaning efficiency were measured due to the repulsive force between the contaminated alumina particle and the Ru surface. The highest PRE was achieved in citric acid solution with NaIO4 below 0.01 M at pH 10.

• Journal of the Optical Society of Korea
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• 제15권3호
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• pp.293-299
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• 2011

In this study, we demonstrated Fourier-domain/swept-source optical coherence tomography (FD/SS-OCT) at a center wavelength of 800 nm for in vivo human retinal imaging. A wavelength-swept source was constructed with a semiconductor optical amplifier, a fiber Fabry-Perot tunable filter, isolators, and a fiber coupler in a ring cavity. Our swept source produced a laser output with a tuning range of 42 nm (779 to 821 nm) and an average power of 3.9 mW. The wavelength-swept speed in this configuration with bidirectionality is 2,000 axial scans per second. In addition, we suggested a modified zero-crossing method to achieve equal sample spacing in the wavenumber (k) domain and to increase the image depth range. FD/SS-OCT has a sensitivity of ~89.7 dB and an axial resolution of 10.4 ${\mu}m$ in air. When a retinal image with 2,000 A-lines/frame is obtained, an acquisition speed of 2.0 fps is achieved.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.424-424
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• 2008

Dye-sensitized Solar Cell (DSC) is a new type of solar cell by using photocatalytic properties of $TiO_2$. The electric potential distribution in DSCs has played a major role in the operation of such cells. Models based on a built-in electric field which sets the upper limit for the open circuit voltage(Voc) and/or the possibility of a Schottky barrier at the interface between the mesoporous wide band gap semiconductor and the transparent conducting substrate have been presented. $TiO_2$ thin films were deposited on the FTO substrate by Nd:YAG Pulsed Laser Deposition(PLD) at room temperature and post-deposition annealing at $500^{\circ}C$ in flowing $O_2$ atmosphere for 1 hour. The structural properties of $TiO_2$ thin films have investigated by X-ray diffraction(XRD) and atomic force microscope(AFM). Thickness of $TiO_2$ thin films were controlled deference deposition time and measurement by scanning electron microscope(SEM). Then we manufactured a DSC unit cells and I-V and efficiency were tested using solar simulator.

• 한국광학회지
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• 제28권2호
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• pp.75-82
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• 2017

초정밀도를 요구하는 반도체 소자 공정에서 웨이퍼의 위치와 반복정밀도를 파장의 수백분의 일로 오차가 거의 없는 상태에서 제어하기 위해 위치변위 레이저 간섭계가 필요하다. 특히 제조공정에서는 생산단가의 인하압박으로 인해 웨이퍼의 대형화가 시도되고 있고 이에 따라 넓은 변위량을 측정하면서 나노미터 급의 위치 정밀도를 지닌 레이저 간섭계가 더욱 절실하게 요구된다. 이런 기술적인 문제를 해결하기 위해서 간섭계에 사용되는 송수신 광학계에도 특별한 광학적인 고안이 필요하게 된다. 본 논문에서는, 송수신 광학부로서 단순하게 콜리메이팅 렌즈만을 사용하는 기존의 방식 대신에, GRIN 렌즈-콜리메이팅 렌즈-무초점 광학계로 구성되는 새로운 형식의 조금 복잡한 형태의 광학구조를 제안하였고 이를 통해 반사된 후 되돌아와 간섭계로 결합되는 광신호의 효율을 약 100배 정도 높일 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.87-87
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• 1999

본 연구에서는 Pulsed Laser Deposition(이하 PDL)방법을 이용하여 Si기판에 (Ba,Sr)TiO3(이하 BST)박막을 MFS-FET(Metal-Ferroelectric-Semiconductor Field-effect Transistor)구조로 제조하였으며 BST박막의 강유전성이 BST 박막에 유도되는 응력에 어떤 영향을 받는지 살펴보았다. 본 연구에서는 완충막을 사용함으로써 BST박막과 완충막간의 격자부정합을 이용하여 BST박막에 강유전성을 유도하려고 하였다. 또한 MFS-FET구조의 BST박막에 유도되는 응력조절을 위하여 BST박막과 완충막의 두께를 변화하였으며 XRD를 통한 구조 분석 및 C-V test를 통한 전기적 특성을 관찰을 하였다. PLD법을 통해서 epitaxial 성장된 BST 박막에서는 Si에 epitaxial 성장된 완충막과의 격자부정합에 의한 BST박막내의 자발분극의 발생이 예상된다. 따라서, 본 연구는 강유전체의 자발분극에 의하여 발생되는 C-V 이력현상이 BST박막과 완충막과의 격자부정합에 의한 응력에 의해 발생될 것으로 예상하여, BST 박막에 유도되는 응력과 C-V 이력현상의 관계를 통하여 상온에서 상유전성을 갖는 BST가 응력에 의하여 어느 정도의 강유전성을 나타내는지를 밝히기 위해 진행되었다. 본 연구에서 사용된 완충막은 YSZ(Yttria Stabilized Zirconia)박막으로 0.4mTorrO2 분위기 하에서 600~80$0^{\circ}C$의 온도에서 증착하여 상형성을 살펴보았고 $700^{\circ}C$에서 epitaxial 성장을 확인하였으며 두께는 30~$\AA$으로 변화하였다. 또한 BST박막은 완충막과의 전압분배를 고려해 300~2000$\AA$으로 두께를 변화를 시키며 증착하였다. MFS 구조에서 Al 전극을 사용하여 완충막과 BST박막간의 두께 변화에 따른 Capacitance - Voltage(C-V) 측정을 하였으며 이를 통하여 강유전상의 특성인 C-V 이력현상을 관찰하였다. 그 결과 YSZ 박막에서는 C-V 이력현상이 나타나지 않았으며 BST 박막에서는 약 1.2V의 C-V이력현상이 보였다.