Arsenic Precipitation in Heavily Arsenic-Doped Czochralski Silicon

Heavily arsenic-doped Czochralski (HAs-CZ) silicon is an important substrate material for manufacturing power electronic devices. The arsenic impurities may be in a supersaturated status in a certain temperature range during the HAs-CZ silicon crystal growth or the device fabrication. Then, whether and how the arsenic impurities can precipitate in HAs-CZ silicon is an intriguing and practically significant issue that has never been addressed. Herein, it is first found that arsenic precipitation can occur in HAs-CZ silicon when subjected to appropriately prolonged anneals at 550-950 degrees C. The resulting second-phase precipitates are confirmed to be of orthorhombic SiAs phase, with the lattice parameters of a = 7.12 angstrom, b = 9.11 angstrom, and c = 9.00 angstrom, through systematic transmission electron microscopy characterizations. Moreover, it is discovered that the presence of vacancies/interstitial silicon atoms in HAs-CZ silicon promotes/inhibits arsenic precipitation.