DEVELOPMENT OF AN ELECTROCHEMICAL OXYGEN SENSOR FOR CZOCHRALSKI SILICON MELTS

An electrochemical oxygen sensor based on stabilized zirconia was developed for measurements of the oxygen concentration in molten silicon. The mixture of Mn and MnO was found to be an appropriate system for the generation of the reference oxygen partial pressure which should be close to that of oxygen in the silicon melt. The free-energy of solution of oxygen in molten silicon was evaluated by calibration experiments. A prototype sensor was tested to measure the oxygen content in the silicon melt in a commercial Czochralski puller. The difference in the radial oxygen concentration between center and periphery increased with increasing crucible rotation. This result is consistent with the experience in silicon crystal growth as well as with recent numerical and experimental results on the impact of crucible rotation on the flow patterns in silicon melts in an industrial-size Czochralski crucible.