Publications (2)0.62 Total impact

  • Chulgi Song · W. Namkoong · S. Chin · T. Ahn · S. Lee · J. Kyoung · J. Kim · Y. Jang · Ilsin An ·
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    ABSTRACT: 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 ′ZrO 2/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 Al2O 3 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.
    Journal- Korean Physical Society 09/2008; 53(3). DOI:10.3938/jkps.53.1650 · 0.42 Impact Factor
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    ABSTRACT: Crystal growth and haze formation on photomasks become serious problems in UV lithography. As the wavelength becomes shorter, photons carry more energy, so the chances of having a photochemical reaction become much higher. Pellicle, adhesive, residue from cleaning or resist strip process, and any contaminant in air can react with UV to form unwanted crystals and a haze layer on reticles. These will reduce the light transmission during exposure process. Thus, frequent mask inspection and periodic mask cleaning are needed to overcome these problems. However, these will in turn increase manufacturing cost and reduce mask life. Thus, a proper mask inspection tool is required to provide early warning of haze formation. In this work, we devised a new ellipsometric technique to investigate the inner surface of mask without removing pellicle. Ellipsometry is known to have mono-layer sensitivity and it can be used to measure any film or partial film formed on non-patterned spot in early stage of growth. However, when a pellicle covers the surface of mask, the ellipsometric data reflected from surface are extremely distorted due to the non-normal transmission through the pellicle. Thus, data analysis becomes extremely difficult without knowing the optical properties of pellicles. In order to solve this problem we developed compensation technique in which two blank pellicles are situated in the optical path in a way to compensate the polarization changes caused by the pellicle on mask. With this method, the conventional ellipsometry spectra of {Delta, Psi} are deduced.
    Proceedings of SPIE - The International Society for Optical Engineering 04/2008; 6922. DOI:10.1117/12.772151 · 0.20 Impact Factor