Investigation of stress at SiO2/4H-SiC interface induced by thermal oxidation by confocal Raman microscopy

Stress at an SiO2/4H-SiC interface was investigated by using confocal Raman microscopy. Measurements were gathered while sequentially etching the SiO2 film on 4H-SiC. A shift of the folded transverse optical E2 mode peak toward low wavenumbers was observed in a 50 nm thick SiO2/4H-SiC, and this shift remained constant for samples with an SiO2 thickness greater than 10 nm. This implies that stress was generated at the SiO2/4H-SiC interface and accumulated in the SiO2 region during the thermal oxidation process. We investigated the influence of annealing in NO on stress generation, while the calculated stresses suggested similar values. Thus, we conclude the NO post-annealing has no drastic effect on stress relaxation at an SiO2/4H-SiC interface.