Optical characterization of 4H-SiC by far ultraviolet spectroscopic ellipsometry

We have developed a far UV spectroscopic ellipsometer system working up to 9 eV, and applied it to the characterization of three 4H-SiC samples with different surface conditions [i.e., as-received and chemical mechanical processing (CMP) processed 4H-SiC bulk substrates and a 4H-SiC epi sample]. Pseudodielectric functions ε₁ and ε₂ clearly demonstrate the excellent surface sensitivity of the far UV ellipsometry system as it distinguishes the improvements provided by CMP process. Simulation results of ellipsometer data indicate the existence of a damaged subsurface layer in the as-received 4H-SiC bulk substrate. The investigation of sample surfaces using atomic force microscopy confirms the results of ellipsometry measurements.