Study of Defect Generated During Cu/Black Diamond CMP Process
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Study of Defect Generated During Cu/Black Diamond CMP Process Shaoyu WU, Ning LI, J. M. KANG, T. W. M. LAM, B. LIN, T. SELVARAJ, S. P. ZHAO, R. KUMAR and P. D. FOO Institute of Microelectronics, DSIC-MD, 11 Science Park Road, Singapore 117685
ABSTRACT Black Diamond (BD) is gaining popularity as a low k dielectric for copper/low k integration. However, because of lower hardness and more hydrophobic in nature of BD film surface comparing with those of the conventional oxide, some specific defects appear during CMP process of Cu/BD patterned wafers. In this study, the patterned wafer inspection systems, AIT II, and SEM review station are used to review and to classify such defects generated from CMP process. Using conventional Cu/Oxide CMP process, the percentage of these specific defects from Cu/BD CMP is typically more than 60 of total defect count. By modifying the composition of slurry with new additives and optimization of polishing and cleaning parameters, the total defect count can be reduced by 80%, in which the amount of specific defects is less than 5% of total defect count. INTRODUCTION As minimum device dimensions are reduced below 0.1µm, the increase in propagation delay, cross-talk noise, and power dissipation of the interconnect structure become limiting factors for integrated circuits (1, 2). To address these problems, low k dielectric/Cu integration was considered as the main solution (3,4). Black Diamond (BD), developed by Applied Materials with k value of about 2.9, is one of most promising low k candidates and is widely investigated (5-7). During the integration of BD with copper by damascene technology, the litho, etch, wet clean, PVD, ECP and finally chemical mechanical polishing (CMP) processes are applied. More challenges of BD than conventional silicon oxide will be faced during integration (8). For Cu/BD CMP process, the defectivity is more concerned because of lower hardness and higher hydrophobicity of BD film comparing with those of the conventional oxide. In this paper, The reduction of Cu/BD CMP related specific defect is studied by modified slurry composition as well as polishing and cleaning processes. The specific defect is analysed and classified by AIT 2, SEMVision and EDX. EXPERIMENTAL The 5k Å of USG film was deposited on Si wafer by PECVD, followed by 5k Å of BD deposited by PECVD. After normal litho, etch, wet clean processes, Ta and copper seed were deposited by IMP, followed by Cu ECP. So obtained wafers are used for CMP defect study in this work. Mirra-Mesa manufactured by Applied Materials was used to perform CMP process and slurries were supplied by Cabot Microelectronics and Rodel Corp. AIT 2 from KLA-Tencor was used for the measurement of total defect counts,
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Semvision integrated with EDX from Applied Materials was used for cl
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