23 April 2001 Observation of titanium-silicide via backside etching
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As IC device dimensions get smaller and smaller, not only do the formation and nature of silicide on the active silicon area become increasingly critical but so does the need for silicide inspection. The ability to inspect the silicide itself is especially important at electrical failure sites. In this paper we describe a straightforward sample preparation method which enables us, after removal of the substrate, to observe silicide from the back side using a scanning electron microscope (SEM). This method was used in combination with photo-emission microscopy (PEM) to localize the exact site of leaky junctions. With this method the silicide grains of different phases can easily be observed over large areas. It was found that in the leaking sites only the large grain C54 phase of TiSi2 was present and never the small grain C49 phase. In this paper we explain junction leakage in connection with phase transformation of titanium silicide, and show that the C54 phase which is normally desired for its low resistance may be problematic when the active Si areas are very small or when the titanium layer thickness is too thin. We also demonstrate that this method makes gate oxides, contact misalignment and other front-end issues readily observable.
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E. M. Fleuren, E. M. Fleuren, Xiao-Mei Zhang, Xiao-Mei Zhang, } "Observation of titanium-silicide via backside etching", Proc. SPIE 4406, In-Line Characterization, Yield, Reliability, and Failure Analysis in Microelectronic Manufacturing II, (23 April 2001); doi: 10.1117/12.425264; https://doi.org/10.1117/12.425264

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