Deuteron activation analysis of ultra-trace carbon in boron-doped Si single crystals

Abstract

The charged particle activation analysis of ultra-trace carbon in boron-doped silicon with the12C(d,n)13N reaction has been developed. In order to apply13N substoichiometric separation to determine carbon in silicon, we studied the rapid dissolution of silicon using nitric acid as the13N carrier. Its amounts were as small and definite as possible and the nitrogen oxide gas produced during the dissolution was collected. Silicon was dissolved for 6 min in a mixture of hydrofluoric acid, acetic acid and phosphoric acid, which contained potassium nitrate as the13N carrier and nitrogen oxide was collected in the sodium hydroxide solution. In order to combine the dissolution method with13N substoichiometric separation, the conditions for steam distillation as pre-separation were also refined in relation to increases in the amount of carrier. Nitrogen-13 was separated substoichiometrically after silicon dissolution and steam distillation. This analytical procedure was used to determine carbon in boron-doped CZ−Si. Carbon at 0.7–12.7·1015 atoms/cm3 was determined with good reproducibility. It took less than 30 min to start the radioactivity measurement after the end of iradiation. The detection limit was 2·1013 atoms/cm3 (0.2 ppb).