디지털 홀로그래피를 이용한 포토리소그래피 공정 제품 패터닝의 폭과 단차 측정

신주엽(Ju Yeop Shin),강성훈(Sung Hoon Kang),마혜준(Hye Joon Ma),권익환(Ik Hwan Kwon),양승필(Seung Pil Yang),정현철(Hyun Chul Jung),홍정기(Chung Ki Hong),김경석(Kyeong Suk Kim) 한국비파괴검사학회 2016 한국비파괴검사학회지 Vol.36 No.1

반도체 산업은 우리나라 주력산업중 하나로 매년 꾸준한 성장세를 보이며 지속적인 성장을 하고 있다. 이러한 반도체 산업에서의 중요한 기술은 소자의 고 집적화이다. 이는 면적당 메모리 용량을 증가시키는 것으로 핵심역할을 하는 것이 바로 포토리소그래피 기술이다. 포토리소그래피란 마스크의 표면에 빛을 쬐어 생기는 그림자를 웨이퍼 상에 인쇄하는 기술이며 반도체 제조공정에서의 가장 중요한 공정이다. 이러한 공정을 통해 나온 패터닝을 분석 시에 폭과 단차의 균일성을 측정한다. 이에 따라 본 논문은 포토리소그래피 공정이 적용된 시험편 패터닝에 폭과 판 사이와의 단차를 투과형 디지털 홀로그래피를 구성하여 측정하고자 한다. 투과형 디지털 홀로그래피 간섭계를 구성하고 시험편에 임의의 9포인트를 설정하여 각 포인트를 측정하고 상용장비인 SEM (scanning electron microscopy)과 alpha step으로 측정한 결과와 비교하고자 한다. 투과형 디지털 홀로그래피는 측정시간이 타 기법에 비에 짧다는 장점과 배율렌즈를 사용하기 때문에 저 배율에서 고 배율로 변경하여 측정할 수 있는 장점을 가지고 있다. 실험 결과로부터 투과형 디지털 홀로그래피가 포토리소그래피가 적용된 패터닝 측정에 유용한 기술임을 확인할 수 있었다. The semiconductor industry is one of the key industries of Korea, which has continued growing at a steady annual growth rate. Important technology for the semiconductor industry is high integration of devices. This is to increase the memory capacity for unit area, of which key is photolithography. The photolithography refers to a technique for printing the shadow of light lit on the mask surface on to wafer, which is the most important process in a semiconductor manufacturing process. In this study, the width and step-height of wafers patterned through this process were measured to ensure uniformity. The widths and inter-plate heights of the specimens patterned using photolithography were measured using transmissive digital holography. A transmissive digital holographic interferometer was configured, and nine arbitrary points were set on the specimens as measured points. The measurement of each point was compared with the measurements performed using a commercial device called scanning electron microscope (SEM) and Alpha Step. Transmission digital holography requires a short measurement time, which is an advantage compared to other techniques. Furthermore, it uses magnification lenses, allowing the flexibility of changing between high and low magnifications. The test results confirmed that transmissive digital holography is a useful technique for measuring patterns printed using photolithography.

디지털 마이크로 홀로그래피를 이용한 짚신벌레의 운동성 측정

김석(Seok Kim),이상준(Sang Joon Lee) 한국가시화정보학회 2008 한국가시화정보학회 학술발표대회 논문집 Vol.- No.2

In field of fluid mechanics, digital holography is one of useful measurement techniques due to non-intrusiveness and optical approach method. In the present study, a micro holographic PTV (HPTV) system was used to experimentally investigate the locomotion of bio-sample. Locomotion of paramecium was tested using digital micro holography. Paramecium was about 170~290㎜ long and had ciliary around body. Two locomotion modes were measured by digital holography. Its velocity and radius of motion were measured quantitatively. Through these research works, digital micro holography with a microscope will be useful to visualize 3D flows in bio-fluid flows.

Elemental Image Synthesis for Integral Imaging Using Phase-shifting Digital Holography

Min-Ok Jeong,김남,박재형 한국광학회 2008 Current Optics and Photonics Vol.12 No.4

We propose a method generating elemental images for the integral imaging using 4-step phase- shifting digital holography. Phase shifting digital holography is a way recording the digital hologram by changing the phase of the reference beam and extracting the complex field of the object beam. Since all 3D information is captured by phase-shifting digital holography, the elemental images for any specifications of the lens array can be generated from single phase-shifting digital holography. In experiment, phase-shifting is achieved by rotating half- and quarter- wave plates and the resultant interference patterns are captured by a 3272×2469 pixel CCD camera with 27 μm×27 μm pixel size.

이중푸리에변환을 이용한 2 파장 디지털 홀로그래픽 연구

신상훈,정원기,유영훈,Shin, Sang-Hoon,Jung, Won-Ki,Yu, Young-Hun 한국광학회 2010 한국광학회지 Vol.21 No.3

디지털 홀로그램을 이용하여 상을 재생 할 때 재생상의 크기는 재생거리와 파장의 함수이다. 이러한 재생거리와 파장 의존성을 제거하기 위하여 이중푸리에변환법이 제안되었고, 이중푸리에변환을 이용하면 일정 크기의 재생상을 얻을 수 있다. 일반적으로 사용된 광원의 파장보다 큰 단차의 높낮이 측정은 단일파장 디지털 홀로그래픽 방식으로 측정이 가능하지 않기 때문에 2 파장홀로그래피가 제안되었는데, 두 파장에서 얻어진 각각의 재생상의 크기가 같아야 하는 제약이 있다. 본 연구에서는 투과 및 반사형 2 파장 디지털 홀로그래픽 현미경을 이용하여 각각의 파장별로 홀로그램을 촬영하고 이중푸리에변환을 이용하여 재생함으로써 두개의 파장에서 얻어진 재생상의 크기를 같게 만들어 주는 과정 없이 단차를 가진 샘플의 3차원 높낮이 측정을 할 수 있었다. The size of a reconstructed image depends on the reconstruction distance and wavelength. The double fourier transform method is proposed to eliminate the dependence on the reconstruction distance and wavelength. We can get a fixed reconstructed image size by using the double fourier transform method. Two wavelength digital holography is proposed to measure the step height, which is larger than a single wavelength. The two image size of different wavelength holograms should be the same in order to apply two wavelength digital holography. We use two wavelength digital holography and double fourier transforms to measure the step height. The measured data were reasonable and we found that the double fourier transform is useful in two wavelength digital holography.

반사형 디지털 홀로그래피를 이용한 허니콤 구조의 회로선 폭 측정

정현일(Hyunil Jung),신주엽(Ju-Yeop Shin),이설희(SeolHee Yi),권익환(Ik-Hwan Kwon),정현철(Hyunchul Jung),김경석(Kyeong-Suk Kim) 한국비파괴검사학회 2017 한국비파괴검사학회지 Vol.37 No.3

반도체 제작 시 포토리소그래피 공정은 설계한 전기회로패턴을 기판 위에 옮기는 공정이다. 기판에 가공된 패턴이 설계한 전기회로와 정확히 일치하게 전사되었는지의 여부는 반도체 고집적화 연구에서 매우 중요하며, 주로 AFM, FE-SEM, Alpha Step, CIRCLTM Suite 등의 장비를 이용하여 검사한다. 본 논문에서는 디지털 홀로그래피를 이용한 검사 방법을 제시하였다. 이를 위해 포토리소그래피 공정으로 허니컴 패턴이 제작된 반사형 시험대상체 상에 임의로 9곳의 측정점을 지정하였다. 반사형 디지털 홀로그래피를 이용하여 허니컴 패턴으로 제작된 회로의 선 폭을 측정하고, 그 결과로부터 회로가 설계한대로 정확히 전사되었는지 여부를 확인하였다. 반사형 디지털 홀로그래피로 측정한 결과값의 신뢰성을 확인하기 위하여 통상적으로 쓰이는 검사장치인 AFM과 FE-SEM으로 측정하여 그 결과를 비교, 검증하였다. During semiconductor fabrication, the photolithography process is a transfer printing process used to replicate the designed electric circuit pattern onto a wafer or circuit board. For studies related to high integration of semiconductors, it is very important to confirm whether the printed pattern is fabricated with complete fidelity. AFM, FE-SEM, Alpha Step, and CIRCLTM Suite are typically used systems for inspecting the printed pattern. In this paper, an inspection method using digital holography is proposed. For this purpose, nine measuring points on a reflective object, which the honeycomb pattern in the photolithography process was printed on, were selected arbitrarily. The line width of the honeycomb pattern printed on the wafer was measured using the reflection type of the digital holography. Subsequently, it was confirmed whether the pattern was correctly printed or not. In order to verify the reliability of the reflection type of the digital holography, the results of the digital holography were compared with those of AFM and FE-SEM, and it was confirmed that the deviation from AFM and FE-SEM was within 3% and 0.5%, respectively.

2-단계 위상 천이 디지털 홀로그래피를 이용한 이진 정보 광 암호화 기법

변현중,길상근,Byun, Hyun-Joong,Gil, Sang-Keun 한국광학회 2006 한국광학회지 Vol.17 No.5

보안 시스템에서 2-단계 위상 천이 홀로그래피를 이용하여 이진 정보 광 암호화 기법을 제안하였다. 위상 천이 디지털 간섭계는 CCD 카메라를 이용하여 위상과 크기 정보를 기록할 수 있는 기법이다. 2-단계 위상 천이는 0과 ${\pi}/2$의 위상 천이 각을 갖도록 PZT 거울을 움직여서 구현하였다. 이진 정보와 암호키는 랜덤 코드와 랜덤 위상으로 표현하였고, 디지털 홀로그램은 푸리에변환 홀로그램으로 간섭무늬는 CCD를 이용하여 256 레벨의 양자화 된 광세기로 획득되었다. 데이터 복원 시 DC 성분 제거 방법을 사용하였다. 컴퓨터 모의실험을 통하여 데이터 복원과 양자화 과정에서의 양자화 레벨 변화량과 디지털 홀로그램 간섭무늬의 오차 픽셀수에 따른 오차 분석을 수행하였다. 이 결과를 이용하여 정보의 광학적 암호화에 적용이 가능함을 확인하였다. We propose an optical encryption/decryption technique for a security system based on 2-step phase-shifting digital holography. Phase-shilling digital holography is used for recording phase and amplitude information on a CCD device. 2-step phase-shifting is implemented by moving the PZT mirror with phase step of 0 or ${\pi}/2$. The binary data and the key are expressed with random code and random phase patterns. The digital hologram is a Fourier transform hologram and is recorded on CCD with 256 gray level quantization. We remove the DC term of the digital hologram fur data reconstruction, which is essential to reconstruct the original binary input data/image. The error evaluation fer the decrypted binary data is analyzed. One of errors is a quantization error in detecting the hologram intensity on CCD, and the other is generated from decrypting the data with the incorrect key. The technique using 2-step phase-shifting holography is more efficient than a 4-step method because 2-step phase-shifting holography system uses less data than the 4-step method for data storage or transmission. The simulation shows that the proposed technique gives good results fur the optical encryption of binary information.

Secret Key Sharing Cryptosystem using Optical Phase-shifting Digital Holography

전석희,길상근 한국광학회 2019 Current Optics and Photonics Vol.3 No.2

A new secret-key-sharing cryptosystem using optical phase-shifting digital holography is proposed. The proposed secret-key-sharing algorithm is based on the Diffie-Hellman key-exchange protocol, which is modified to an optical cipher system implemented by a two-step quadrature phase-shifting digital holographic encryption method using orthogonal polarization. Two unknown users’ private keys are encrypted by two-step phase-shifting digital holography and are changed into three digital-hologram ciphers, which are stored by computer and are opened to a public communication network for secret-key-sharing. Two-step phase-shifting digital holograms are acquired by applying a phase step of 0 or π/2 in the reference beam’s path. The encrypted digital hologram in the optical setup is a Fourier-transform hologram, and is recorded on CCDs with 256 quantized gray-level intensities. The digital hologram shows an analog-type noise-like randomized cipher with a two-dimensional array, which has a stronger security level than conventional electronic cryptography, due to the complexity of optical encryption, and protects against the possibility of a replay attack. Decryption with three encrypted digital holograms generates the same shared secret key for each user. Schematically, the proposed optical configuration has the advantage of producing a kind of double-key encryption, which can enhance security strength compared to the conventional Diffie-Hellman key-exchange protocol. Another advantage of the proposed secret-key-sharing cryptosystem is that it is free to change each user’s private key in generating the public keys at any time. The proposed method is very effective cryptography when applied to a secret-key-exchange cryptosystem with high security strength.

디지털 홀로그래피를 이용한 광학적 비밀키 교환 방법

길상근 水原大學校 2016 論文集 Vol.30 No.-

Private information encryption is very important in the public communication network. In this paper a new optical secret key exchange method is proposed by using digital holography. The proposed method is presented by modifying the Diffie-Hellman key exchange protocol in cipher system, and it is optically implemented by using 2-step phase-shifting digital holography based on orthogonal polarization. Encrypted digital holograms containing the user’s private key information are transmitted to the other user as public keys, and these are used for generating a shared secret key. The numerical simulation results of the proposed system show the application of Diffie-Hellman key proptocol with high security strength.

프레즈넬-불루스타인 변환을 이용한 2파장 디지털 홀로그래픽 연구

신상훈,김두철,유영훈,Shin, Sanghoon,Kim, Doocheol,Yu, Younghun 한국광학회 2012 한국광학회지 Vol.23 No.6

Dual-wavelength holography has a better axial range than single-wavelength holography, allowing unambiguous phase imaging. The size of a reconstructed image depends on the reconstruction distance and wavelength. The two phase image sizes of different wavelength holograms should be the same in order to apply dual-wavelength holography. The Fresnel-Bluestein transform method is proposed to eliminate the dependence on the reconstruction distance and wavelength. We found that the Fresnel-Bluestein transform is very useful for making different reconstructed image sizes experimentally. Also we applied the Fresnel-Bluestein transform to make the same reconstruction image size in dual wavelength holography. 이 파장 디지털 홀로그래피는 단파장 디지털 홀로그래피에 비해 보다 큰 단차를 얻는데 사용할 수 있다. 이파장 홀로그래피 방법을 이용하기 위해서는 각각의 파장에서 얻은 홀로그램으로부터 재생된 위상 이미지 크기가 동일하여야하는데, 위상 이미지 크기는 재생거리와 파장에 의존한다. 이러한 문제점을 해결하기 위하여 프레즈렐-불루스타인 변환법이 제안되었다. 이변환법은 재생상의 크기를 재생거리와 파장에 의존하지 않고 자유롭게 만들 수 있다. 본 연구에서는 프레즈렐-불루스타인 변환법을 이파장 홀로그래피에 적용하여 파장에 의존하지 않는 동일한 위상 재생상을 얻을 수 있음을 실험적으로 확인하였다.

Dual-wavelength Digital Holography Microscope for BGA Measurement Using Partial Coherence Sources

Hyungjun Cho,Doocheol Kim,유영훈,정원기,Sanghoon Shin 한국광학회 2011 Current Optics and Photonics Vol.15 No.4

Dual-wavelength holography has a better axial range than single-wavelength holography, allowing unambiguous phase imaging. Partial coherence sources reduce coherent noise, resulting in improved reconstructed images. We measured a ball-grid array using dual-wavelength holography with partial coherence sources. This holography method is useful for measurement samples that exhibit coherence noise and have a step height larger than the single wavelength used in holography.