Analysis and removal of impurities and defects in reactive ion etched silicon using a novel depth-profiling technique

Abstract

The analysis and removal of residual damage induced by reactive ion etching of silicon were studied with a new ultrashallow depth-profiling technique of silicon. In this technique, which is known to give a depth resolution of better than 0.5 nm [Lau et al., Appl. Phys. Lett. 63, 78 (1993)], a few atomic layers of silicon were oxidized by an ultraviolet/ozone exposure at room temperature and subsequently removed by an HF wet etch. In the present study, the compositional changes during depth profiling and the amount of silicon removed per oxidation/etch cycle were estimated by x-ray photoelectron spectroscopy. In addition, Rutherford backscattering spectroscopy was used to confirm the compositional changes and to measure defect depth distributions. Further, surface-charge spectroscopy was applied to determine the minimum oxidation/etching required to completely remove Fermi-level pinning associated with the residual damage. The results showed that these profiling and analysis techniques, when applied in a coherent manner, can provide an accurate picture of the residual damage induced by reactive ion etching. More importantly, the study also showed that the oxidation/etching technique can be applied as a well-controlled process for removing the residual damage.