Evidence of Ti-related Inclusions in an Al Alloy Interconnecting Layer for Nanometer 256MBit DRAM Semiconductor Devices Characterized by TEM, STEM, EELS Elemental Mapping, and XEDS Linescan


With the introduction of high aspect ratio and steep geometries in deep-subquarter-micron dynamic random access memory (DRAM) device, it becomes more and more critical to understand the formation of undesired intermetallic Ti-Al phases in Al-metallization and thus better-control the profile of interconnectors. In this article, Ti-related inclusions in Metal 1 (M1) interconnecting layer (an AlCu-0.5% alloy) originated from the bottom Ti liner were characterized with an Analytical TEM. Samples were cleaved from nanometer 256Mbit dynamic random access memory DRAM devices. The TEM employed is a JEOL 2010F with a field emission gun (FEG) and running at 200KV acceleration voltage. Correlations among transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) elemental mapping, and x-ray energy dispersive spectroscopy (XEDS) elemental linescan were established. The results here not only provide important feedbacks to semiconductor product integration and optimization, but also demonstrate the full-functionality of the start-of-the-art analytical TEM in investigations of nanometer semiconductor devices.

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The authors would like to thank our colleague at Infineon Technologies Richmond for their encouragements and supports in conducting the TEM analyses and writing up the article. Special thanks to Art O’Donnell and Klaus Althoff for reviewing the final manuscript, Bart Seefeldt for proof-reading drafts from the beginning to the end, and Thomas Taylor, Mark Luzar, Richard Chapman, and Eric McDaniel for their technical guidance and stimulating discussions during various stages of the experiments. Finally, many thanks also go to Maurice Goodall for his patience in preparing the TEM foils.

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Correspondence to Wei Wayne Zhao.

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Zhao, W.W., Graca, S. Evidence of Ti-related Inclusions in an Al Alloy Interconnecting Layer for Nanometer 256MBit DRAM Semiconductor Devices Characterized by TEM, STEM, EELS Elemental Mapping, and XEDS Linescan. MRS Online Proceedings Library 737, 82 (2002). https://doi.org/10.1557/PROC-737-F8.2

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  • dynamic random access memory
  • DRAM
  • semiconductor
  • transmission electron microscopy
  • TEM
  • energy loss electron spectroscopy EELS
  • scanning transmission electron microscopy STEM
  • EDS
  • linescan
  • elemental mapping