Alpha-activation analysis of nitrogen in boron-doped silicon single crystal

The rapid dissolution of silicon and the substoichiometric separation of18F were studied in order to determine nitrogen in a boron-doped silicon single crystal by α activation analysis via15N(α,n)18F. The silicon dissolution method was developed by using a nitric acid-based solution containing a known amount of ammonium fluoride, instead of hydrofluoric acid, as the18F carrier. The silicon could be dissolved to a depth of 100 μm with a 10 mm Ø in 9 minutes. The conditions for18F steam distillation and substoichiometric precipitation as lanthanum fluoride were improved. 50% of the fluorine could be separated substoichiometrically even though the carrier amount was increased from 6–12 mmol to more than 16 mmol in order to add it to the dissolving solution. This dissolution method and improved substoichiometric separation were used to determine nitrogen in a boron-doped silicon single crystal. The nitrogen concentration was found to be less than the detection limit (50 ppb).