Quantitative detection of small amount of nitrogen in Czochralski-grown silicon crystals

We successfully detected small amounts of nitrogen with a concentration of 3 x 10(13) cm(-3) in a nitrogen-doped Czochralski-grown Si crystal. O-N-O complexes (or shallow thermal donors) were observed through infrared spectroscopy of electronic transition between hydrogen-like levels of the complexes. This method is very sensitive and shows promise as a means of quantitatively detecting nitrogen in Si wafers of 10(12)-10(14) cm(-3). We found that almost all the N was in the form of O-N-O complexes when the N concentration is less than 1 x 10(14) cm(-3). Therefore, conventional methods that measure localized vibrational modes due to N-N and N-N-O complexes cannot detect nitrogen of less than 1 x 10(14) cm(-3), not only because of the detection limit but also the lack of such vibrational centers.