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10 September 2007 Microstructure of 100 nm damascene copper overburden and lines
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A detailed understanding of the crystallography of metallic conductors in modern interconnect systems is essential if we are to understand the influence of processing parameters on performance and reliability. In particular we must be able to evaluate the grain size, crystallographic orientation and residual elastic stress for interconnect lines having widths of tens of nm. Transmission electron microscopy might be the obvious choice, but sample preparation and small sample size make this technique unattractive. On the other hand, electron backscatter diffraction, EBSD, in a scanning electron microscope provides a very attractive tool. Sample preparation can be relatively simple, especially if one investigates the structures immediately after CMP; whole wafers may be measured if desired. One limitation to EBSD is that good diffraction patterns are obtained only from free surfaces and from a limited depth, say a few hundred nm in copper. Here EBSD will be used to compare structures for the pads and 100-nm lines in two variants of a commercial copper damascene interconnect structure. EBSD data collection will be discussed as optimized for characterizing differences in the texture, which were attributed to differences in the processing. By a unique approach to EBSD mapping we found that neither the texture nor the grain size of the overburden, as represented by the contact pads, propagated into the 100 nm lines, though they did propagate into some wider lines.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
R. H. Geiss and D. T. Read "Microstructure of 100 nm damascene copper overburden and lines", Proc. SPIE 6648, Instrumentation, Metrology, and Standards for Nanomanufacturing, 664808 (10 September 2007);

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