Measurement of Low Concentration Nitrogen in Czochralski Silicon by Infrared Absorption Spectroscopy

Abstract

Nitrogen in Czochralski silicon mainly forms pair with oxygen at low concentration, in contrast to forming NN pair at high concentration. To measure nitrogen concentration in NO pair form, local vibration modes of NO family such as NO, NOO and NOO2 were examined. By removing LVMs by NN family and oxygen complexes from the spectra, weak absorption lines hidden by them were successfully delineated. To identify them, their dependence on the N concentration, and annealing temperature and time was examined and compared to the annealing behavior of NN family and far infrared absorption of shallow thermal donor family composed of NO family. The LVM candidates were identified, 769 and 945 cm-1 lines for NO, 736 and 1022 cm-1 lines for NOO, 973 and 1002 cm-1 lines for NOO2 and 855 and 1064 cm-1 lines for ONO configurations. Nitrogen concentration in the NO family was obtained from the sum of the absorbance of these lines