INTERLABORATORY DETERMINATION OF OXYGEN IN SILICON FOR CERTIFIED REFERENCE MATERIALS

The oxygen content and relative transmission of Czochralski silicon containing interstitial oxygen in three different concentrations has been determined in a multilaboratory exercise to produce sets of certified reference materials (CRMs). A calibration factor of (3.02 +/- 0.19) x 10(17) cm-2 linking the oxygen concentration to the peak absorption of the interstitial oxygen band can be derived in good agreement with the International Oxygen Coefficient 1988 (IOC-88) study. This calibration factor corresponds to a measurement temperature of 310 K. However, the present work has identified differences in the infrared data of the order of 5 % between measurements made with dispersive and Fourier transform spectrometers (FTS). These differences arise from the emissivity of the samples which is detected in many FTS as a spurious contribution to the oxygen absorption. It follows that the FTS data have to be corrected generally so that they agree with the results obtained with dispersive spectrometers (DS). Consequently, the calibration factor was deduced from DS results only. It is proposed that the aptitude of different infrared (IR) instruments to measure accurately the oxygen absorption coefficient can be tested with the aid of the CRM sets with certified oxygen concentrations and relative transmissions.