Investigation of Laminated High-k Oxides by Using Vacuum Ultraviolet Spectroscopic Ellipsometry

안일신,Chulgi Song,W. Namkoong,S. Chin,T. Ahn,S. Lee,J. Kyoung,Y. Jang 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3

Zirconium oxide (ZrO2) is suggested as a good candidate for a high-k dielectric. For the storage capacitor in a dynamic random access memory, a multi-stack of ZrO2 and Al2O3 is reported to reduce the leakage current and to secure a high capacitance. In this case, however, the thickness and the properties of each layer need to be precisely controlled in order to deposit a well-defined laminated structure. Although conventional spectroscopic ellipsometry is one of the best techniques to characterize multilayer films, it shows poor sensitivity to high-k materials due to its limited spectral range. Thus, in this work, vacuum ultraviolet spectroscopic ellipsometry (VUV SE) and high-resolution transmission electron microscopy were employed for the laminated structure of `ZrO2/Al2O3/ZrO2' on a silicon substrate, where the oxide layers were prepared by using an atomic layer deposition technique. As the optical properties of the ZrO2 films were so sensitive to the preparation process, many considerations were required for the analysis of the VUV SE data. From the analysis, we found that the optical properties of the bottom ZrO2 film depended on its own thickness, as well as on the deposition temperature of the subsequent Al2O3 layer. Meanwhile, those of the top ZrO2 layer showed a dependence on the crystalline structure of the bottom ZrO2 and on the thickness of the interfacial Al2O3 layer.

[테마기획6/차세대 분석평가장비] 타원편광분석 기술의 끝없는 변모

안일신 대한기계학회 2005 기계저널 Vol.45 No.3

Calibration-Free Multichannel Ellipsometry for Retardance Measurement

안일신,오혜근,J. . Kyung,K. Y. Bang,김옥경,R. W. Collin 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.2

When rotating sample configurations are adopted in transmission ellipsometry, the retardance of a sample can be measured without a calibration process to find the azimuths of optical elements. Two configurations are employed: (1) rotation of sample between polarizer and analyzer whose transmission axes are fixed in parallel; (2) dual rotations of sample and compensator between polarizer and analyzer. The former is simple in design. Meanwhile, the latter shows high sensitivity for low retardance. As the transmission axes of both polarizer and analyzer are fixed in these configurations, any errors related to the source polarization or polarization sensitivity of the detector can be avoided. Moreover, both systems are easy to construct, because complicated electronics are not required to control the azimuths of optical elements. By using a multichannel detection system, retardance over 300 to 800 nm can be measured in a simple and fast way.

Use of Array Detector for Real-time Spectoscopic Ellipsometer

안일신,김세덕 한양대학교 이학기술연구소 1999 이학기술연구지 Vol.1 No.-

고속분광 엘립소미터를 위해 photodiode array 검출기를 이용하였다. 이때 각 부품의 시간적 요구사항을 만족시키기 위하여 array 구동용 전자회로를 직접 설계 제작하였는데 512의 채널을 읽어 내는데 필요한 시간인 read-out time이 편광기의 회전 속도를 제한하였다. 하지만 광학 주기당 3-4회의 부분 적분법을 적용함으로써 한 쌍의 엘립소미터 스펙트럼을 측정하는데 20 m초 이내의 측정속도를 실현할 수 있었다. 각 채널로부터 일정한 반응값을 얻을 수 있었으며 연속측정에서도 평균정도에 따라 0.04에서 0.007도 정도의 정밀도를 얻었다. We employed photodiode array as a detection system for fast scanning spectroscopic ellipaometer. Controller for data acquisition was designed to accommodate all timing requirements. Pixel read-out time for 512 channels limited the rotational frequency of polarizer. However, when we employed partial-integration method to take 3 or 4 spectra per optical cycles, we could achieve the fastest data acquisition speed of less than 20 ms for a pair of ellipsometric spectra. We obtained quite uniform response from ll channels and the repetitive measurements showed 0.04-0.007 degree of precision depending on averaging.

Use of Array Detector for Real-time Spectroscopic Ellipometer

안일신,김세덕 한양대학교 이학기술연구소 1999 이학기술연구지 Vol.1 No.-

The Real Time Optical Studies of the Electrochromism in Tungsten Oxide Thin Films

An, Ilsin,Kim, Ok-kyung 漢陽大學校 基礎科學硏究所 1995 基礎科學論文集 Vol.14 No.-

텅스텐 옥사이드 박막에 계단식 전압을 걸면서 생기는 채색 및 탈색 과정을 real time spectroscopic ellipsometry 기술을 이용하여 분석하였다. 채색된 박막의 광학 스펙트럼이 상당한 금속성을 보이는 것이 Drude free electron 성분으로부터 추론되었다. Bruggeman effective medium theory를 이용하여 분석한 실시 데이타로부터 박막의 채색된 정도와 박막 속으로 주입된 전하량 사이에는 상관관계가 있음이 밝혀졌다. Real time spectroscopic ellipsometry has been employed to investigate the coloration and bleach cycles in tungsten oxide thin films during the application of step-like potentials. The optical properties of colored films showed strong metallic behavior, which could be deduced from the Drude component of the films. We applied Bruggeman effective medium theory to analyze the real time data set and found strong correlation between the magnitude of coloration and the total charge injected into the film.

Spectroscopic Ellipsometry Study of the Composition of Cobalt-SiO Thin Film

Lee, Jae-Ho;An, Il-Sin 한양대학교 이학기술연구소 2002 이학기술연구지 Vol.4 No.-

Cobalt(Co)와 SiO가 서로 다르게 섞인 target을 이용한 co-sputtering을 박막의 광학적 물성을 조절하기 위하여 이용하였다. Co와 SiO의 박막에서 volume fractions를 추론하기 위하여 effective medium 이론을 이용하였으며, 또한 각각의 박막에서의 각 성분의 원자적 백분율을 추론하기 위하여 XPS 측정을 하였다. 그 결과, 각 박막에서의 구성 성분의 volume fraction과 원자적 백분율 사이의 상관관계를 찾아내었다. Co-sputtering with targets of different mixture of cobalt(Co) and SiO was used to control the optical properties of thin films. Effective medium theory was used to deduce the volume fractions of Co and SiO in the film. Also XPS measurement were carried out to deduce the atomic oercent of each component in the film. As result, strong correlation was found between the volume fraction and the atomic percent of each composition in the film.

The Optical Properties of Silver Bulk and Silver Thin Films

Kim,Ok-Kyung,An, Ilsin 漢陽大學校 自然科學硏究所 1996 自然科學論文集 Vol.15 No.-

스퍼트링 증착기술을 이용하여 은박막을 생장시켰다. 생장 초기에 있는 은박막에서 비정상의 가시 영역 에너지 흡수가 일어나는데 이 흡수대는 박막이 자랄수록 장파장대로 이동하여 간다. 이 현상은 금속 입자의 크기와 주변 입자간의 상호작용에 의한 것이다. 다시 말해, 은입자의 한 쪽 표면에서 반대 쪽 표면 사이에 일어나는 강한 전기 쌍극자 진동에 의한 것인데 이는 3차원적인 은덩이 속에서는 볼 수 없는 현상이다. 은입자로 이루어진 박막의 광학적 성질을 로렌쯔 모델을 사용하여 설명하였다. 또한 박막과 덩이 형태의 은에 있어서의 광학적 성질의 차이점을 논하였다. Silver thin films were prepared by rf-magnetron sputtering technique. Silver thin films in the initial growth stages showed anomalous absorption in the visible wavelength region, which moved to longer wavelengths as film grew. These are related to the size of the metal clusters and interaction between them. In other words, a strong dipole oscillation of electrons occurs from one side of cluster to the other, which is absent in bulk silver. A simple Lorentz model was adopted to account for the optical properties of grain-like metal thin films. Also the differences in optical properties between bulk and thin film silver were discussed.

Null Ellipsometry를 이용한 Stainless Steel표면의 물분자 흡착

이재호,안일신,남현수 한양대학교 이학기술연구소 2001 이학기술연구지 Vol.3 No.-

Stainless steel표면의 물분자의 흡착을 연구하기 위해 Null ellipsometry를 이용하였다. 단층박막 모델과 effective medium 이론을 이용하여, 물 분자의 surface coverage를 얻었다. 상대습도 증가에 따른 surface coverage의 변화로부터 stainless steel표면의 물분자의 resident time을 유도할 수 있었다. Null ellipsometry was employed to study the adsorption of water molecules on stainless steel surface. Using a single layer optical model and effective medium theory, the surface coverage of water molecules was obtained. From the variation of surface coverage upon humidity rise, we could derive the resident time of water molecules on the stainless steel surface. It was estimated as 1O-7sec or longer.

Real-time Optical Studies in the UV Range of the Annealing of Zirconium-oxide Thin Films in Vacuum

전현경,안일신 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.1

A multichannel spectroscopic ellipsometer is developed for real-time studies of thin films in a vacuumin the UV range. This system is mounted on a vacuum chamber to study the crystallizationprocess of zirconium-oxide (ZrO2) thin film. The optical spectra of ZrO2 thin film are collectedduring the elevation of temperature. From the trend in the spectrum, we find that a thresholdtemperature for crystallization exists. Moreover, the crystallization occurs gradually over a certainrange of temperatures between the threshold temperature and a critical temperature for full crystallization. The evolution of the dielectric function shows the development of critical peaks around6.2 eV and 7.3 eV along with a shift of the absorption edge. To the best of our knowledge, this isthe first in-situ study performed by using real-time vacuum UV spectroscopic ellipsometry, and wedescribe the system in detail.