Micro and nano Raman characterization of SiGe structures obtained by Ge implant in Si

Arianna LUCIA, CNIS Sapienza Università di Roma - G. MARGUTTI, LFoundry

There is a general interest in Silicon/Germanium alloys in the semiconductor industry, due to their peculiar properties (like the enhanced electron mobility, for example). SiGe alloy layers can be deposited by CVD (Chemical Vapor Deposition) but the lattice mismatch between the alloy and the underlaying Silicon can be an issue. To overcome this problem Lfoundry decided to use Germanium implantation on Silicon with the additional advantage to selectively form SiGe alloy only in certain areas of the silicon wafer, followed by the proper thermal budget that supplies the energy to make the alloy. Several bare silicon wafer were implanted and annealed with different thermal conditions. Raman spectroscopy was used to look for the SiGe peaks, then it’s used to characterize SiGe quantity and the lattice strain. The Raman spectrometer is installed in the Lfoundry open laboratory.

Green and near-UV laser were used for this characterization: the use of near-UV laser gives information from the surface (depth about 10 nm) and the use of green laser gives information from a larger volume (depth about 500 nm). 

The preliminary data showed that it’s possible to make SiGe alloy using Germanium ion implantation.

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