Applications of micro-Raman spectroscopy in salicide characterization for Si device fabrication

This article demonstrates that micro-Raman spectroscopy is a very powerful technique for the study of a variety of problems related to metal salicides for Si device fabrication. In addition to its versatile nature and ease of use, this technique provides some unique capabilities that complement the commonly used tools for Si device characterization. Phase identification of the $TiSi2$ C54, C49, and C40 phases as well as NiSi and $NiSi2$ can be achieved easily using Raman spectroscopy. The phase transition process from NiSi to $NiSi2$ has also been successfully monitored. Raman band assignments for C40 $TiSi2$ and NiSi are also made in order to have a better understanding of the Raman spectra. Thickness measurement of ultrathin salicide films from 45 nm down to 6 nm has been accurately performed using attenuation of the Si Raman signal at 520 cm⁻¹, and film uniformity can also be evaluated using the same peak. Local orientations of the NiSi grains are studied by the relative intensity of the NiSi Raman peaks with micron spatial resolution, which provides complementary information to the space-averaged x-ray diffraction result.