• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.361-361
• /
• 2013

비냉각 적외선 검출소자는 빛이 전혀 없는 환경에서도 사물을 감지하는 열상장비의 핵심소자이다. 마이크로볼로미터 적외선 검출기는 상온에서 동작하며, 온도안정화를 위해 TEC를 장착하여 진공패키지로 조립된다. 패키지는 진공을 유지할 수 있도록 일반적으로 메탈로 제작되며, 단가 감소 및 생산성 증대를 위해 wafer level packaging 방법을 이용한다. 마이크로볼로미터의 특성은 패키지의 진공 변화에 매우 민감하다. 센서의 감도를 증가시키기 위해서는 진공환경을 유지해야 한다. 볼로미터 소자의 특성은 상압에서 열전도는 기판과 멤브레인 사이의 에어갭을 통해 열손실을 야기하므로 센서의 반응도가 현저히 줄어든다. 에어갭이 1 um 정도 되더라도 그 사이에 존재하는 열전도가 가능하므로 진공을 유지하여 열고립 상태를 증대시킬 수 있다. 이에 본 연구에서는 소자의 동작시 압력, 즉 진공도가 볼로미터 소자의 반응도 특성에 미치는 영향을 조사하였다. 마이크로볼로미터 소자는 $2{\times}8$ 어레이 형태로 제작하였으며, metal pad를 각 단위셀에 배치하였으며, 공통전극으로 한 개의 metal pad를 넣어 설계하였다. 흡수체로써 VOx를 사용하였으며, 열 고립구조를 위해 2.5 um 공명 흡수층의 floating 구조로 멤브레인을 형성하였다. 진공패키지는 메탈패키지를 제작하여 볼로미터 칩을 TEC 위에 장착하였으며, 신호의 감지를 위해 가변저항을 매칭시켰다. 반응도는 신호 대 잡음 값을 획득하여 소자에 도달하는 적외선 에너지에 대해 반응하는 값을 계산에 의해 얻어내는 것이다. 픽셀 크기는 $50{\times}50$ um이며, 패키지 조립 공정 후 온도변화에 따른 저항 측정을 통해 TCR 값을 얻었다. 이때 TCR은 약 -2.5%/K으로 나타났다. $2{\times}8$의 4개 단위소자에 대해 측정한 값은 균일하게 TCR 값이 나타났다. 광반응 특성은 볼로미터 단위소자에 대해서 먼저 고진공(5e-6 torr) 하에서 측정하였으며, 반응도는 25,000 V/W의 값을 나타내었고, 탐지도는 약 2e+8 $cmHz_{1/2}$/W로 나타났다. 패키지의 압력 조절을 위해 TMP 및 로터리 펌프를 이용하여 100 torr에서 1e-4 torr의 범위에서 압력조절 밸브를 이용하여 질소가스의 압력으로 진공도를 변화시켰다. 적외선 반응신호는 압력이 증가함에 따라 감소하였으며, 2e-1 torr의 압력에서 신호의 크기가 감소하기 시작하여 5 torr에서 반응도의 1/2 값을 나타냄을 알 수 있었다. 30 torr 이상에서는 신호가 잡음값 과거의 동일하여 신호대 잡음비가 1로 나타남을 알 수 있었다. 또한 진공도 변화에 대해, 흑체온도에 따른 반응도 및 탐지도의 특성을 조사한 결과를 발표한다. 반응도의 증가를 위해 진공도는 진공도는 1e-2 torr 이하의 압력을 유지해야 함을 본 실험을 통해 알 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.330-332
• /
• 2013

소 분위기에서 플라즈마 표면 처리의 경우 기판 표면에 존재하는 수소와 탄소 유기물들이 산소와 반응하여 $H_2O$와 $CO_2$ 등으로 제거되며 표면에 오존 결합을 유도하여 표면 에너지를 증가시키는 것으로 알려져 있다. ZnO 나노구조물을 성장시키는 방법으로는 MOCVD (Metal-Organic Chemical Vapor Deposited), PLD (Pulsed Laser Deposition), VLS (Vapor-Liquid-Solid), Sputtering, 습식화학합성법(Wet Chemical Method) 방법 등이 있다. 그중에서도 습식화학합성법은 쉽게 구성요소를 제어할 수 있고, 저비용 공정과 낮은 온도에서 성장 가능하며 플렉서블 소자에도 적용이 가능하다. 그러므로 본 연구에서는 플라즈마 표면처리에 따라 표면에너지를 변화하여 습식화학합성법으로 성장시킨 ZnO nanorods의 밀도를 제어하고 photolithography 공정 없이 패터닝 가능성을 유 무를 판단하는 연구를 진행하였다. 기판은 Si wafer (100)를 사용하였으며 세척 후 표면에너지 증가를 위한 플라즈마 표면처리를 실시하였다. 분위기 가스는 Ar/$O_2$를 사용하였으며 입력전압 400 W에서 0, 5, 10, 15, 60초 동안 각각 실시하였다. ZnO nanorods의 seed layer를 도포하기 위하여 Zinc acetate dehydrate [Zn $(CH_3COO)_2{\cdot}2H_2O$, 0.03 M]를 ethanol 50 ml에 용해시킨 후 스핀코팅기를 이용하여 850 RPM, 15초로 5회 실시하였으며 $80^{\circ}C$에서 5분간 건조하였다. ZnO rods의 성장은 Zinc nitrate hexahydrate [$Zn(NO_3)_2{\cdot}6H_2O$, 0.025M], HMT [$C6H_{12}N_4$, 0.025M]를 deionized water 250 ml에 용해시켜 hotplate에 올리고 $300^{\circ}C$에서 녹인 후 $200^{\circ}C$에서 3시간 성장시켰다. ZnO nanorods의 성장 공정은(Fig. 1)과 같다. 먼저 플라즈마 처리한 시편의 표면에너지 측정을 위해 접촉각 측정 장치[KRUSS, DSA100]를 이용하였다. 그 결과 0, 5, 10, 15, 60 초로 플라즈마 표면 처리했던 시편이 각각 Fig. l, 2와 같이 $79^{\circ}$, $43^{\circ}$, $11^{\circ}$, $6^{\circ}$, $7.8^{\circ}$로 측정되었으며 이것을 각각 습식화학합성법으로 ZnO nanorods를 성장 시켰을 때 Fig. 3과 같이 밀도 차이를 확인할 수 있었다. 이러한 결과를 바탕으로 기판의 표면에너지를 제어하여 Fig. 4와 같이 나타나며 photolithography 공정없이 ZnO nanorods를 패터닝을 할 수 있었다. 본 연구에서는 플라즈마 표면 처리를 통하여 표면에너지의 변화를 제어함으로써 ZnO nanorods 성장의 밀도 차이를 나타냈었다. 이러한 저비용, 저온 공정으로 $O_2$, CO, $H_2$, $H_2O$와 같은 다양한 화학종에 반응하는 ZnO를 이용한 플렉시블 화학센서에 응용 및 사용될 수 있고, 플렉시블 디스플레이 및 3D 디스플레이 소자에 활용 가능하다.

• Korean Journal of Materials Research
• /
• v.8 no.6
• /
• pp.532-537
• /
• 1998

The purpose of this study was to investigate the behavior of ozone in DI water and the reaction with wafers during the semiconductor wet cleaning process. The solubility of ozone in DI water was not only dependent on the temperature but also directly proportional to the input concentration of ozone. The lower the initial ozone concentration and the temperature, the longer the half-life time of ozone. The reaction order of ozone in DI water was calculated to be around 1.5. The redox potential reached a saturation value in 5min and slightly increased as the input ozone concentrations increased. The completely hydrophilic surface was created in Imin when HF etched silicon wafer was cleaned in ozonized DI water containing higher ozone concentrations than 2ppm. Spectroscopic ellipsometry measurements showed that the chemical oxide formed by ozonized DI water was measured to be thicker than that by piranha solution. The wafers contaminated with a non-ionic surfactant were more effectively cleaned in ozonized DI water than in piranha and ozonized piranha solutions.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.22 no.2
• /
• pp.73-77
• /
• 2012

Co-(0.8 wt%) and Ce-(0.4 wt%) doped cubic zirconia ($ZrO_2$ : $Y_2O_3$ = 80 : 20, 70 : 30, 60 : 40, 50 : 50 wt%) single crystals grown by a skull melting method were heat-treated in $N_2$ at $1000^{\circ}C$ for 5 hrs. The orange, yellowish brown and brown colored as-grown single crystals were changed into either brownish red, yellow and green color after the heat treatment. Before and after the heat treatment, the YSZ (yttria-stabilized zirconia) single crystals were cut for wafer form (${\phi}6.5mm{\times}t2mm$). The optical and structural properties were examined by UV-VIS spectrophotometer and X-ray diffraction. Absorption by $Ce^{3+}(^2F_{5/2,7/2}(4f){\rightarrow}^2T_g(5d^1))$, $Co^{2+}(^4A_2(^4F){\rightarrow}^4T_1(^4F)$ or $^4T_1(^4P))$ and $Co^{3+}$, change of ionization energy and lattice parameter were confirmed.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.20 no.1
• /
• pp.7-11
• /
• 2010

The reduction of optical losses in mono-crystalline silicon solar cell by surface texturing is a critical step to improve the overall cell efficiency. In this study, we have changed the sub-micrometer structure on the micrometer pyramidal structure by 2-step texturing. The Ag particles were coated on the micrometer pyramid surface in $AgNO_3$ solution, and then the etching with hydrogen fluoride and hydrogen peroxide created even smaller nano-pyramids in these pyramids. As a result, we observed that the changes of size and thickness of nano structure on pyramidal surface were determined by $AgNO_3$ concentration and etching time. Using 2-step texturing, the surface of wafers is etched to resemble the rough surface of a lotus leaf. Lotus surface can reduce average reflectance from 10% to below 3%. This reflectance is less than conventional textured wafer including anti-reflection coating.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.45 no.4
• /
• pp.29-34
• /
• 2008

Generally, for conventional 3-D Hall sensor it is general that the sensitivity for $B_z$ is about 1/10 compared with those for $B_x$ or $B_y$. Therefore, in this work, we proposed 3-D Hall sensor with new structures. We have increased the sensitivity about 6 times to form the trench using anisotropic etching. And we have increased the sensitivity for the $B_z$ by 80 % compared with those of $B_x$ and $B_y$ using deposition of the ferromagnetic thin films on the bottom surface of the wafer to concentrate the magnetic fluxes. Sensitivities of the fabricated sensor with Ni/Fe film for $B_x,\;B_y$, and $B_z$ were measured as 361mV/T, 335mV/T, and 286mV/T, respectively. It has also showed sine wave of Hall voltages over a $360^{\circ}$ rotation. A packaged sensing part was $1.2{\times}1.2mm^2$. The measured linearity of the sensor was within ${\pm}3%$ of error. Resolution of the fabricated sensor was measured by $1{\times}10^{-5}T$.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.5
• /
• pp.183-190
• /
• 2013

In this paper, we propose an improved anisotropic diffusion model for micro-crack detection in heterogeneously textured surface of polycrystalline solar wafers. Due to the nature of the image sensor, the gray-level of the diagonal micro-crack is non-uniform. Thus, the conventional algorithms can't fully detect diagonal micro-cracks when the number of iteration is not enough. However, the increasing of the iteration number leads to increase computation time and detects micro-crack thicker than the original micro-crack. In order to overcome this drawback, we use the gradient of north, south, east, and west directions as well as extended directions. To calculate the diffusion coefficients, we compare the gradients of conventional directions and extended directions and apply the larger gradient values to the coefficient function. This is because the proposed method reflects the information of diagonal micro-crack. Comparing to Tsai et al.'s and Ko and Rheem's, the proposed algorithm shows superior efficiency in detecting the diagonal micro-cracks with less iterations in the images of polycrystalline solar wafers. In addition, it also shows that the thickness of segmented micro-crack is similar to the orignal micro-crack.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.1
• /
• pp.263-272
• /
• 2011

Highly luminescent and monodisperse InP quantum dots (QDs) were prepared by a non-organometallic approach in a non-coordinating solvent. Fatty acids with well-defined chain lengths as the ligand, a non coordinating solvent, and a thorough degassing process are all important factors for the formation of high quality InP QDs. By varying the molar concentration of indium to ligand, QDs of different size were prepared and their absorption and emission behaviors studied. By spin-coating a colloidal solution of InP QD onto a silicon wafer, InP QD thin films were obtained. The thickness of the thin films cured at 60 and $200^{\circ}C$ were nearly identical (approximately 860 nm), whereas at $300^{\circ}C$, the thickness of the thin film was found to be 760 nm. Different contrast regions (A, B, C) were observed in the TEM images, which were found to be unreacted precursors, InP QDs, and indium-rich phases, respectively, through EDX analysis. The optical properties of the thin films were measured at three different curing temperatures (60, 200, $300^{\circ}C$), which showed a blue shift with an increase in temperature. It was proposed that this blue shift may be due to a decrease in the core diameter of the InP QD by oxidation, as confirmed by the XPS studies. Oxidation also passivates the QD surface by reducing the amount of P dangling bonds, thereby increasing luminescence intensity. The dielectric properties of the thin films were also investigated by capacitance-voltage (C-V) measurements in a metal-insulator-semiconductor (MIS) device. At 60 and $300^{\circ}C$, negative flat band shifts (${\Delta}V_{fb}$) were observed, which were explained by the presence of P dangling bonds on the InP QD surface. At $300^{\circ}C$, clockwise hysteresis was observed due to trapping and detrapping of positive charges on the thin film, which was explained by proposing the existence of deep energy levels due to the indium-rich phases.

• Composites Research
• /
• v.27 no.5
• /
• pp.183-189
• /
• 2014

Experimental considerations have been performed to obtain the clear optical microscopic images of graphene oxide which are useful to probe its quality and morphological information such as a shape, a size, and a thickness. In this study, we investigated the contrast enhancement of the optical images of graphene oxide after hydrazine vapor reduction on a Si substrate coated with a 300 nm-thick $SiO_2$ dielectric layer. Also, a green-filtered light source gave higher contrast images comparing to optical images under standard white light. Furthermore, it was found that a image channel separation technique can be an alternative to simply identify the morphological information of graphene oxide, where red, green, and blue color values are separated at each pixels of the optical image. The approaches performed in this study can be helpful to set up a simple and easy protocol for the morphological identification of graphene oxide using a conventional optical microscope instead of a scanning electron microscopy or an atomic force microscopy.

• Journal of IKEEE
• /
• v.24 no.1
• /
• pp.161-169
• /
• 2020

In order to reduce the manufacturing cost of MCU chips used in applications such as wireless chargers and USB-C, compared to DP-EEPROM (Double Poly EEPROM), which requires 3 to 5 additional process masks, it is even more necessary MTP(Multi-Time Programmable), which is less than one additional mask and have smaller unit cell size. In addition, in order to improve endurance characteristics and data retention characteristics of the MTP memory cell due to E/P(Erase / Program) cycling, the distribution of the V_TP(Program Threshold Voltage) and the V_TE(Erase Threshold Voltage) needs to be narrow. In this paper, we proposed a current-type BL S/A(Bit-Line Sense Amplifier) circuit, WM(Write Mask) circuit, BLD(BL Driver) circuit and a algorithm, which can reduce the distribution of program and V_T and erase V_T, through compare the target current by performing the erase and program pulse of the short pulse several times, and if the current specification is satisfied, the program or erase operation is no longer performed. It was confirmed that the 256Kb MTP memory fabricated in the Magnachip semiconductor 0.13㎛ process operates well on the wafer in accordance with the operation mode.