Evaluation of Very High Resolution Multi-Wavelength Raman Spectroscopy for In-Line Characterization of Patterned Epitaxial Si1-xGex Layers on Si(100) Wafers

Abstract

Micro-Raman spectroscopy is a very attractive non-destructive in-line technique for characterizing stress/strain of the crystal, as well as crystallinity and Ge content in Si1-xGex. Additionally it requires no sample preparation, provides sub-micron spatial resolution, and requires relatively short measurement time. A polychromator-based, high resolution, multi-wavelength Raman spectroscopy system was evaluated from a manufacturing perspective as a candidate for in-line stress/strain monitoring equipment. Short-term and long-term measurement repeatability and system stability were extensively evaluated using five patterned Si1-xGex/Si(100) wafers with nominal Ge content in the range of 15~35 at% (in 5 at% increments). Three major spectral lines (457.9, 488.0 and 514.5 nm) from a multi-wavelength Ar ion laser were used as the excitation source. The short-term and long-term measurement repeatability was evaluated for three months. A very small range of total variation, less than 0.05cm-1, was measured under all three excitation wavelengths.