UV-Raman deformation coefficients in Si and SiGe alloys

As Si CMOS device scaling issues become increasingly challenging a number of alternatives arise including Si-On-Insulator (SOI) substrates, high-k gate dielectrics, and Strained Si Channel (SSC) devices.~ In the case of SSC structures, the enhancement in electron mobility depends directly on the stress magnitude.~ Raman scattering, particularly in the UV due to short penetration depth, has proven well suited for measuring thin SSC layer stress.~ The technique depends critically on the value taken for the strain shift coefficient ($b)$, which correlates the shift in the phonon frequency with the strain.~ A number of values have been reported in the literature to date using NIR and visible excitation; however, the authors are unaware of previous work performed specifically in the UV. In this work, we have used a combination of HRXRD reciprocal space mapping (RSM) to measure the in-plane strain of high quality Si/SiGe heterostructures and UV-Raman with the 325nm He-Cd line to determine the Si LO phonon deformation coefficient in Si and SiGe alloys with compositions ranging from 10-40{\%} Ge.