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높은 A/R의 콘택 산화막 에칭에서 바닥모양 변형 개선에 관한 연구
황원태,김길호,Hwang, Won-Tae,Kim, Gli-Ho 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.5
The etching technology of the high aspect ratio contact(HARC) is necessary at the critical contact processes of semiconductor devices. Etching the $SiO_{2}$ contact hole with the sub-micron design rule in manufacturing VLSI devices, the unexpected phenomenon of 'profile tilting' or 'bottom distortion' is often observed. This makes a short circuit between neighboring contact holes, which causes to drop seriously the device yield. As the aspect ratio of contact holes increases, the high C/F ratio gases, $C_{4}F_{6}$, $C_{4}F_{8}$ and $C_{5}F_{8}$, become widely used in order to minimize the mask layer loss during the etching process. These gases provide abundant fluorocarbon polymer as well as high selectivity to the mask layer, and the polymer with high sticking yield accumulates at the top-wall of the contact hole. During the etch process, many electrons are accumulated around the asymmetric hole mouth to distort the electric field, and this distorts the ion trajectory arriving at the hole bottom. These ions with the distorted trajectory induce the deformation of the hole bottom, which is called 'profile tilting' or 'bottom distortion'. To prevent this phenomenon, three methods are suggested here. 1) Using lower C/F ratio gases, $CF_{4}$ or $C_{3}F_{8}$, the amount of the Polymer at the hole mouth is reduced to minimize the asymmetry of the hole top. 2) The number of the neighboring holes with equal distance is maximized to get the more symmetry of the oxygen distribution around the hole. 3) The dual frequency plasma source is used to release the excessive charge build-up at the hole mouth. From the suggested methods, we have obtained the nearly circular hole bottom, which Implies that the ion trajectory Incident on the hole bottom is symmetry.
상이한 국제기관의 방법론에 따른 음식물 중 방사능의 유도개입준위의 비교
황원태,김은한,한문희 대한방사선 방어학회 2001 방사선방어학회지 Vol.26 No.4
IAEA, FDA, WHO, CEC를 포함한 상이한 국제기관에서 권고하고 있는 방법론에 따라 국내 방사능 비상계획을 위한 기초자료로 활용하기 위해 음식물의 오염에 대한 유도개입준위를 평가·비교하였다. 원자력발전소의 사고 결과에 중요 핵종인 ^137Cs, ^90Sr, ^131I이 고려되었다. 선량에 대한 개입준위는 ICRP의 신권고 (ICRP-60) 평가체제에 근거하여 적용하였다. 음식물에 대한 유도개입준위는 국제기관에서 권고하고 있는 방법론에 따라 약 10배까지 차이를 나타내며, 전반적으로 FDA와 WHO 방법론에 근거한 유도개입준위는 IAEA와 CEC 방법론에 근거한 유도개입준위에 비해 보수적 (보다 낮은 값)이었다. 유도개입준위에 대한 결정 연령군으로 우유는 모든 핵종에 대해 3개월 유아, 나머지 대부분의 음식물의 경우 ^137Cs은 성인, ^90Sr은 15세, ^131I은 5세로 나타났다. Using the different procedures suggested by the recognized organizations including IAEA, FDA, WHO and CED, derived intervention levels (DILs) against contamination of foodstuffs were evaluated for considerations in radiological emergency planning in Korea. Three radionuclides important in terms of the consequence due to accidents at a nuclear power plant, i.e., ^137Cs, ^90Sr and ^131I, were considered. Intervention level for dose based on new recommendation of the ICRP (ICRP-60) was applied. The DILs for the same foodstuff differ by up to a factor of 10. In most cases, the DILs based on FDA and WHO approaches were more conservative than those based on IAEA and CEC approaches. A critical age group for milk was infant of 3 month for all radionuclides. In most foods except milk, a critical age group was adult, 15 yr and 5 yr for ^137Cs, ^90Sr and ^131I, respectively.
원자력 사고후 장기피폭에 대한 개입을 위한 피폭선량 금전가 산정의 개선된 방법론
황원태,김은한,서경석,최영길,한문희 대한방사선 방어학회 2002 방사선방어학회지 Vol.27 No.2
원자력시설의 정상 운영시 일반인에 대한 단위 집단선량의 금전가 (피폭선량 금전가) 모델을 기본으로, 사고후 만성피폭에 대해 보다 적용 타당한 모델을 제안하였다. 아울러 우리나라 경제 환경자료를 사용하여 제안된 모델에 근거하여 평가한 피폭선량 금전가를 정상 운영시로부터 유도된 값을 수정없이 그대로 사고후 만성피폭에 적용한 값과 비고, 분석하였다. 제안된 방법론에 근거할 경우 집단선량은 같다하더라도 피폭받은 집단내 개인선량의 불균일성 차이에 따라 피폭선량 금전가는 상당히 다르게 나타났다. 또한 할인율도 피폭선량 금전가 결정에 있어서 중요한 요소로 작용하였다. A more practice approach for the determination of monetary values of the unit collective dose for intervention against long-term exposure following a nuclear accident was proposed. In addition, the monetary values of the unit collective dose estimated from the proposed approach were compared with those estimated from the previous model, which are derived from assumptions of routine exposure and the same values are applied in a nuclear accident without modification, using Korean economic data. The monetary values based on the proposed approach showed a distinct difference depending on inequity in the distribution of individual doses. The discounting rate was also an important factor in determination of monetary values of the unit collective dose.