Oxygen Precipitation Properties of Nitrogen‐Doped Czochralski Silicon Single Crystals with Low Oxygen Concentration

Oxygen precipitation properties in the as‐grown defect‐free region of nitrogen‐doped Czochralski silicon (Cz‐Si) single crystals with very low oxygen concentrations ([Oi]) are investigated. At [Oi] values of 4.6–5.9 × 1017 atoms cm−3, oxide precipitates with a high density of 109 cm−3 are generated owing to the enhancement in oxygen precipitation by nitrogen‐doping. In contrast, at [Oi] values of 1.3–2.6 × 1017 atoms cm−3, no oxide precipitates are observed even though the crystals are nitrogen‐doped. Oxygen precipitation in the as‐grown defect‐free region is analyzed based on a thermodynamic model, in which some embryos are assumed to exist in nitrogen‐doped Cz‐Si crystals at high temperatures of crystal growth, and they grow as oxide precipitates during a subsequent cooling process. The analysis of oxygen precipitation indicates that, at [Oi] values below 3 × 1017 atoms cm−3, the radii of oxide precipitates included in the as‐grown Cz‐Si crystals remain small owing to a low growth onset temperature; therefore, oxide precipitates cannot be detected after heat treatment for wafer evaluation. These findings suggest that nitrogen‐doped Cz‐Si crystals with [Oi] values below 3 × 1017 atoms cm−3 are potential materials for power devices, such as insulated gate bipolar transistors. The oxygen precipitation in the as‐grown defect‐free region of nitrogen‐doped Czochralski silicon single crystals with low oxygen concentrations ([Oi]) is investigated. Oxide precipitates are completely suppressed at an [Oi] value below 3 × 1017 atoms cm−3. A thermodynamic model for oxygen precipitation indicates that the growth onset temperature of embryos is extremely low to grow as stable oxide precipitates.