Non-destructive metrology is essential for quality control in semiconductor manufacturing, yet conventional techniques face limitations in characterizing epitaxial silicon-germanium films. This study introduces second harmonic generation (SHG) as a novel approach to address two critical challenges in SiGe process monitoring. First, we demonstrate that SHG can effectively characterize lattice symmetry and defect states in SiGe thin films, enabling discrimination of the effects of different pre-cl