Raman scattering studies of ultrashallow Sb implants in strained Si

Abstract

Sheet resistance (R s ) reductions are presented for antimony doped layers in strained Si. We use microRaman 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.