X-ray absorption studies of high performance Low-k dielectric materials
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X-ray absorption studies of high performance Low-k dielectric materials T. Yoda 1, H. Miyajima, M. Shimada, R. Nakata, H. Hashimoto* 1 Advanced ULSI Process Engineering Department Toshiba Corporation, Semiconductor Company, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8522, Japan *Toray Research Center,Inc. ABSTRACT The XAFS measurement of the MSQ type low-k dielectrics (LKDTM) was conducted to clarify the structure change with and without the EB cure. Furthermore, three different types of other MSQ films, the ladder structure, the random structure and the CVD film, have been investigated as references. We have determined Si-O-Si bond angle and Si-O(Si-C) bond length by fitting the Fourier transformed EXAFS spectra. The ladder structure and the random structure have Si-O-Si bond angle of 133 and 146, respectively. Si-O-Si bond angle of LKDTM film is among that of the ladder and the random structure, and the XANES spectrum of LKDTM film displays two broad features, corresponding to the mixture of both structures. In contrast, Si-O-Si angles of the EB cured LKDTM film and the CVD film resemble each other, and the XANES features of both films are almost identical with that of the random structure. We have confirmed that the EB cure process for LKDTM film makes drastic structure change from the mixture of ladder and random structure to the random network structure.
INTRODUCTION The integration of the multilevel interconnection by damascene Cu with low-k dielectrics is the key technology for SOC (System On Chip) devices. Cu with low-k dielectrics process is widely used for 0.13um and beyond devices. Requirements include high mechanical strength of low-k material to avoid the crack of the film by Cu CMP processes and packaging processes. The EB (Electron Beam) cured process is the most promising candidate to improve the mechanical strength of the MSQ (Methylsilsesquioxane) type low-k dielectrics (LKDTM film; JSR Corporation) without increasing the k value [1]. The structural study of the films is necessary to understand the root cause of the improvement of the mechanical strength by the EB cure. The X-ray diffraction analysis of MSQ ladder polymer derived from gel was already conducted by M.Wada et al [2]. The purpose of this study is to investigate the relation between the local structure and the mechanical strength of the Low-k films. XAFS (X-ray Absorption Fine Structure) is a nondestructive characterization technique, consisting of XANES (X-ray Absorption Near Edge Structure) spectrum and EXAFS (Extended X-ray Absorption Fine Structure) spectrum, which reveals local structure and local symmetry around the atom that absorbs x-rays and emits fluorescence. In this study, we have conducted the XAFS measurement of the MSQ type low-k dielectrics (LKDTM film) to clarify the structure change with and without the EB cure. Furthermore, three
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types of other MSQ films, the ladder structure, the random structure and the CVD film, have been investigated as references. We have determined Si-O-Si bond angle and Si-O (
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