굴절률 차이와 디지털 홀로그래피를 이용한 큰 단차측정
Height Measurement by Refractive Index Difference and Digital Holography
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초록
디지털 홀로그램과 굴절률 차이를 이용하여 사용된 광원의 파장보다 큰 단차를 측정하는 연구를 하였다. 위상차를 측정하여 단차를 측정하는 방식에서는 위상차가 2π보다 큰 경우에는 원리상 단차를 구하기 어렵다. 이를 보완하기 위하여 굴절률 차이를 이용하여 인위적으로 광경로차를 줄여 파장보다 큰 단차를 측정할 수 있는 디지털 홀로그래피 시스템을 구성하였고, 실험적으로 파장의 약 3배 이상의 단차를 측정하였다.
Abstract
Digital holography and refractive index difference are used to measure a high aspect ratio’s patterns. When interference fringes are very closely spaced, the phase data containing high frequencies where 2π ambiguities cannot be resolved. In this technique, the optical path difference is decreased by decreasing the refractive index difference. As a result, we solve the 2π ambiguities. Also, this technique is applicable to measure the refractive index if the shape of the sample is known.
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