Raman scattering studies of ultrashallow Sb implants in strained Si
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Sheet resistance (R s) reductions are presented for antimony doped layers in strained Si. We use micro-Raman spectroscopy to characterise the impact of a low energy (2 keV) Sb implantation into a thin strained Si layer on the crystalline quality and resultant stress in the strained Si. The use of 325 nm UV laser light enables us to extract information from the top ∼9 nm of the strained Si layer. Prior to implantation the Si layer is fully strained with a tensile stress value ∼1.41 GPa, in agreement with the calculated theoretical maximum on a strain relaxed buffer with 17% Ge content. There is a clear decrease in the intensity of the Si Raman signal following Sb implantation. The lattice damage and lattice recovery achieved by subsequent rapid thermal anneal (RTA) is quantified using the amplitude and full width at half maximum (FWHM) of the crystalline Si peak. The shift of the Raman Si peak is a key parameter in the interpretation of the spectra. The ion-implanted sample is studied in terms of a phonon coherence length confinement model. Carrier concentration effects are seen to play a role in the Raman shift following electrical activation of the Sb atoms by RTA.
KeywordsRapid Thermal Anneal Raman Peak Shift Electron Carrier Concentration SiGe Buffer Layer Average Carrier Concentration
Science Foundation Ireland is gratefully acknowledged for funding this project under the Investigator Programme Grant. The authors would like to thank IQE Silicon Compounds Ltd. for providing the strained silicon substrates used in these experiments. We acknowledge ANKA, HASYLAB and the European Community for funding under Contract RII3-CT-2004_506009 (IA-SFS). We are grateful to R. Simon of ANKA for assistance in using the Topas beamline and T. Wroblewski and C. Paulmann for their help at HASYLAB beamline F-1.