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변요한,정지원 한국전기전자재료학회 2002 전기전자재료학회논문지 Vol.15 No.2
The wet etching characteristics of magnetic materials such as NiFe and CoFe were investigated in terms of etch rate and etch profile by using variouus etching solutions (etchants). Among the various etching solutions, HNO$_3$, HCl, and H$_2$SO$_4$were selected for the etching of magnetic materials and showed distinct results. In the case of NiFe films, faster etch rate were obtained with HNO$_3$solution. When NiFe films ere etched with HCl solution, white etch residues were found on the surface of etched films. From FEAES analysis of these etch residues, they were proved to be by-product from the reaction of NiFe with Cl element. CoFe thin films showed the similar trend to the case of NiFe films. They were etched fast in HNO$_3$ solution while Chl solution represented slow etching. The etch profiles of CoFe films showed smooth etch profile but revealed the partial etching around the patterns in HNO$_3$solution of relatively high concentration. It was observed that the etched surface was clean and smooth, and that white etch residues were also remained on the etched films.
TiAlN 박막의 electrical Resistivity에 대한 종착 변수의 영향
송영수,변요한,김혜인,윤진구,김인숙,정지원 한국화학공학회 2002 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.40 No.4
반응성 직류 마그네트론 스퍼터링(dc magnetron reactive sputtering)을 이용하여 N_2 flow rate와 dc power 그리고 중착 압력 등을 주요 변수로 선택하여 TiAIN 박막이 상온에서 증착 되었다. 증착된 박막에 대하여 증착 속도와 electrical resistivity가 조사되었고 결정 구조와 결정도를 알기 위하여 X-ray 회절법이 이용되었다. FESEM을 이용하여 증착된 박막의 grain 크기와 모양 및 표면이 관찰되었다. 증착 속도는 증착 압력의 변화에 대하여 일정하였으나, N_2 flow rate가 증가함에 따라 약간 감소하였고 dc power가 증가함에 따라서 비례적으로 증가되었다. Electrical resistivity는 N_2 flow rate의 변화에 대해서 일정한 값을 나타냈지만, dc power가 증가할수록 감소하는 경향을 보였으며 증착 압력이 증가할수록 증가하였다. TiAIN thin films were deposited at room temperature by varying nitrogen flow rate, dc power and deposition pressure by dc magnetron reactive sputtering. The deposition rate and electrical resistivity of the deposited films were investigated and x-ray diffraction(XRD) was used to examine crystalline structure and crystallinity of the film. Surface morphology and grain shape of the deposited films were observed by using field emission scanning electron microscopy(FESEM). The deposition rate was no noticeable variation for the change of deposition pressure but it was a little decrease with increasing N_2 flow rate and was proportionally increased with increasing dc power. Electrical resistivity was constant with respect to the change of N_2 flow rate but it was decreased as a dc power increased and increased as a deposition pressure increased.
화학 용액 증착법에 의하여 증착된 Bi<sub>3.25</sub>La<sub>0.75</sub>Ti<sub>3</sub>O<sub>12</sub>박막에 대한 결정화 온도의 영향
김혜인,변요한,윤진구,송영수,정지원 한국공업화학회 2002 한국공업화학회 연구논문 초록집 Vol.2002 No.0
비휘발성 메모리에 이용되는 강유전체(ferroelectric)물질에 대한 연구가 최근 활발하게 이루어지고 있다. Bismuth 층상구조로 이루어진 Bi<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub>(BT는 다른 강유전체 물질에 비하여 높은 Curie temperature(675°C), 큰 breakdown strength와 유전상수를 가진다. 그리고 BT에 La이 치환된 형태인 Bi<sub>3.25</sub>La<sub>0.75</sub>Ti<sub>3</sub>O<sub>12</sub>(BLT)는 피로현상이 거의 나타나지 않으며, 큰 분극값을 가지는 등 바보다 개선된 특성을 가지는 것으로 알려져 있어서 이에 대한 많은 연구가 이루어지고 있다. 본 실험에서는 BLT박막이 bismuth acetate, lanthanum acetate와 titanium (diisopropoxide)bis(acetylacetonate)를 전구체로 사용한 화학 용액 증착법에 의하여 제조되었다. 박막의 결정화 단계인 annealing과정의 온도를 650°C와 700˚C 로 변화시키면서 그에 따른 박막의 결정구조, 표면의 결정모양과 전기적 특성을 XRD, FESEM과 RT66A를 이용하여 관찰하였다. XRD pattern으로부터 annealing온도가 박막의 결정도에 큰 영향을 주지 않는 것을 알 수 있었다. 박막의 grain의 크기는 annealing온도가 증가할수록 증가하였다. 650°C와 700°C에서 annealing된 박막은 각각 약 10 μC/㎠와 약 17 μC/㎠의 2Pr값을 가지며, 약 68.75 kV/cm와 약 75 kV/cm의 Ec값을 가졌다. 따라서 650°C에서 annealing된 박막보다 700°C에서 annealing된 박막이 더욱 우수한 전기적인 특성을 가지는 것을 알 수 있었다.
HBr/Ar 플라즈마내에서 Polysilicon 박막의 Nanometer 크기의 패터닝
송영수,변요한,정지원 한국공업화학회 2003 응용화학 Vol.7 No.1
Polysilicon thin films with nanometer-sized patterns were etched in a high density inductively coupled plasma (ICP). The etch characteristics of polysilicon and silicon oxide thin films were examined using HBr/Ar gas chemistry. As the concentration of HBr gas increases, the etch rate of polysilicon film and the etch selectivity of polysilicon to photoresist simultaneously increase. The etch profiles of polysilicon films masked with photoresists were observed for various nanometer-sizeed patterns of 50∼125 nm lines. In this study, the good pattern transfer of polysilicon films with nanometer-sized patterns was achieved using HBr/Ar etch gas.
Lanthanum 조성변화에 따른 강유전체 Bi_(4-x)La_xTi_3O_12 박막의 구조적, 전기적 특성
김혜인,변요한,송영수,정지원 한국공업화학회 2002 응용화학 Vol.6 No.2
Ferroelectric Bi_4-xLa_xTi_3O_12 thin films were prepared by chemical solution deposition using bismuth acetate, lanthanum acetate and titanium isopropoxide as precursors. The BLT thin films were deposited as a function of lanthanum composition. The structure and the surface morphology of the BLT thin films were characterized by x-ray diffraction and field emission scanning electron microscopy. The electrical measurements were performed using a RT66A. The BLT films doped with x=0.75 were found to exhibit better electrical properties than those doped with other La compositions. The remanent polarization (2P_r) and the coercive voltage(V_c) of BLT thin film with x=0.75 were 11.1 μC/㎠ and 1.3V.