Measurement of nitrogen in Czochralski silicon by means of infrared spectroscopy

A novel method for the quantitative measurement of nitrogen in Czochralski silicon by means of low temperature Fourier transform infrared spectroscopy (LT-FTIR) is presented, based on measurement in the far-infrared range. Its main advantage is the high sensitivity to nitrogen, 5×1012 at. cm−3. The method consists in measuring the sample at a temperature less than 15 K, in the spectral range 190–300 cm−1, where the absorption bands related to the electronic transition of the N–O species are present. The samples are prepared by means of a thermal treatment at a suitable temperature (e.g. 650 °C) for a long enough time in order to reach the saturation of the N–O concentration and, therefore, assure that an equilibrium situation is obtained.