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전자 렌즈 Aperture 구조에 따른 마이크로칼럼의 전자빔 특성
최상국,이천희,Choi, Sang-Kuk,Yi, Cheon-Hee 한국광학회 2005 한국광학회지 Vol.16 No.5
마이크로칼럼에 사용되는 전자렌즈는 MEMS 공정으로 정밀하게 가공되어 기존의 전자칼럼에 비하여 광학수차를 최소화 할 수 있으며, 이는 전자칼럼의 성능 향상에 주요한 요소로 작용한다. 따라서 반도체 공정 방식(습식식각과 건식식각)에 의해 형성되는 렌즈구조에 따른 전자 광학계 연구는 중요한 의미가 있다. 마이크로칼럼을 구성하고 있는 전자방출원, 소스렌즈, 디플렉터, 포커스렌즈(Einzel lens) 중에서 전자빔의 특성에 가장 큰 영향을 주는 것은 소스렌즈이다. 본 연구에서는 소스렌즈의 extractor와 limiting aperture의 구조에 따른 전자빔 특성을 조사하였다. Microlens precisely fabricated by MEMS process, is a key component of the Microcolumn, Since, miniaturization can reduces aberrations, microcolumn is expected to have better performance than conventional columns. Depending on the fabrication techniques, the sectional view of micro lens has different shape. In the paper, the effect of the sectional shape of extractor lens and limiting aperture on the focusing property of microcolumns have been studied.
최상국,이천희,Choi, Sang-Kook,Yi, Cheon-Hee 한국광학회 2005 한국광학회지 Vol.16 No.3
생산성 향상을 위하여 정렬된 마이크로칼럼을 이용하여 멀티-전자빔 리소그라피 장치를 개발하였다. 마이크로칼럼은 매우 작은 크기를 가지고 있어 병렬구조로 정렬하여 작동시킬 수 있다. Single Column Module(SCM) 구조의 멀티 전자빔 리소그라피 시스템과 전자칼럼을 제작하여 250 eV에서 300 eV 에너지 범위에서의 저에너지 마이크로칼럼 리소그라피를 성공적으로 수행하였다. 전자방출원에서 방출되는 전자빔의 총 전류가 $0.5\;{\mu}A$일 때, 샘플에서의 전류는 >1 nA으로 측정되었으며 리소그라피 패텅닝에서 사용된 working distance은 $\~1\;mm$였다. A Multiple electron beam lithography system with arrayed microcolumns has been developed for high throughput applications. The small size of the microcolumn opens the possibility for arrayed operation on a scale commensurate. The arrayed microcolumns based on of Single Column Module (SCM) concept has been fabricated and successfully demonstrated. Low energy microcolumn lithography has been operated in the energy range from 250 eV to 300 eV for the generation of nano patterns. Probe beam current at the sample was measured about >1 nA at a total beam current of $0.5\;{\mu}A$ and a working distance of $\~1\;mm$. The magnitude of probe beam current is strong enough for the low energy lithography. The thin layers of PMMA resist have been employed. The results of nano-patterning by low energy microcolumn lithography will be discussed.
정인성,김종환,최상국,배종연,이미영,Chung, In-Sung,Kim, Jong-Ghan,Choi, Sang-Kug,Bae, Jong-Youn,Lee, Mi-Young The Korean Society for Preventive Medicine 2006 예방의학회지 Vol.39 No.2
Objectives : The objective of this study is to assess the factors influencing biological monitoring of textile coating factory workers exposed to N,N-dimethylformamide(DMF). Methods : We studied 35 workers who were occupationally exposed to DMF from 9 textile coating factories. The study was carried out in two phases; summer and winter. While air concentration of DMF, temperature and humidity were assessed in order to monitor the atmospheric conditions, biological monitoring was done to determine the internal dose by analyzing the N-methylformamide(NMF) collected from urine at the beginning and end of the shift. Questionnaires and medical surveillance were also obtained during the two phases. Results : Median air concentrations of DMF in winter and summer were 1.85 ppm and 2.78 ppm respectively. Also the difference between the urinary NMF concentration at the beginning and end of the shift $({\Delta}NMF)$ was always significant in each season (P < 0.001). The correlations between log DMF in air, log end-of-shift urinary NMF (r=0.555, P < 0.001) and log ${\Delta}NMF$ (r = 0.444, P < 0.001) was statistically significant in summer. The temperature, humidity, a shift system and different styles of clothing worn were significantly different during the two phases. In a multivariate analysis, temperature and the concentration of DMF in the air were the main factors influencing biological monitoring of textile coating factory workers. Conclusions : Concerning more comprehensive prevention measures to reduce exposure for those workers occupationally exposed to DMF, dermal exposure conditions such as temperature and humidity together with the air concentration of DMF should be assessed and biological monitoring is necessary to reduce adverse health effects, especially during the summer.
김호섭,김대욱,김영철,최상국,김대용,Kim, Ho-Seob,Kim, Dae-Wook,Kim, Young-Chul,Choi, Sang-Kuk,Kim, Dae-Yong 한국광학회 2003 한국광학회지 Vol.14 No.2
FCM(Fast moving least square reproducing kernel point collocation method) 방식의 simulation tool을 이용하여 전기장으로 구동되는 초소형 전자 렌즈의 구동 특성을 조사·분석하였다. Einzel 렌즈의 retarding mode와 accelerating mode구동에서 포텐셜 분포는 유사하지만, electric field strength는 서로 다른 방향을 갖게 되어 서로 다른 형태의 전자 궤적을 보인다. 동일한 working distance에서 accelerating mode로 구동되는 전자렌즈는 retarding mode로 구동되는 경우보다 매우 높은focusing 전압을 필요로 한다. The analysis of operation characteristics of a miniaturized electrostatic electron lens system called an Einzel lens was performed using a simulation tool of FCM method. The potential distributions of Einzel lenses operated both in retarding and accelerating modes show similar features. But the electric fields determined from the potential distributions show opposite directions, which results in different features in the electron beam trajectory in each mode of operation. For the same working distance, focusing voltage in the accelerating mode is higher than that in the retarding mode.