Masaro Tamatsuka

Enhanced nucleation of oxide precipitates during Czochralski silicon crystal growth with nitrogen doping

Thermal stability of oxide precipitate nuclei has been investigated for Czochralski silicon crystals with nitrogen doping. The experimental result indicates that generation of the grown-in oxide precipitate nuclei stable over 800 °C is enhanced by nitrogen doping. On the other hand, even though we confirmed this existence, doped nitrogen shows no influence on further oxide precipitate nucleation during the isothermal annealing at 600 °C after an epitaxial silicon growth process. Thus, it is found that the nitrogen doping only enhances the oxide precipitate nucleation at higher temperature during crystal cooling. The enhanced precipitate nucleation during the cooling is considered to be through excess vacancies which are suppressed to agglomerate by nitrogen.

MEDIUM FIELD BREAKDOWN ORIGIN ON METAL OXIDE SEMICONDUCTOR CAPACITOR CONTAINING GROWN-IN CZOCHRALSKI SILICON CRYSTAL DEFECTS

The medium field breakdown of metal oxide semiconductor capacitor due to the Czochralski silicon crystal originated defect was studied in view of both electrical and structural analyses. By analyzing the local tunneling current which initiates the medium field breakdown, phenomenological defect sizes were calculated from the local tunneling current by assuming the local oxide thinning model. They were the defect diameter as 5 to 50 nm and the local oxide thinning as ~25 nm. These data were confirmed by direct defect observation using high precision defect isolation procedure followed by transmission electron microscopy. Direct observation revealed that the real defect size was ~200 nm which correlated well with other recently reported works. The real local oxide thinning,however,was not as large as phenomenological calculation. To explain the differences between phenomenological and real local oxide thinning, the poly-Si grain protrusion induced stress model was proposed.