Anisotropic strain evaluation induced in group IV materials using liquid-immersion Raman spectroscopy

We evaluated anisotropic biaxial strain induced in silicon channel region of metal-oxide-semiconductor field effect transistor (MOSFET) as well as novel channel or source/drain materials such as silicon germanium (SiGe) and germanium tin (GeSn) using liquid-immersion Raman spectroscopy. Uniaxial stress in Si channel region predicted by the simulation was well reproduced by Raman measurement. For the evaluation of SiGe and GeSn, the phonon deformation potentials (PDPs) were derived for the first time, because they are indispensable to obtain the biaxial strain. The PDPs of SiGe indicate clear Ge concentration dependence, which is decreasing with Ge concentration, while the PDPs of GeSn with less than 3.2% Sn concentration exhibit almost constant. Using the derived PDPs, we obtained the anisotropic biaxial strains introduced in the finite patterned SiGe precisely.