Phosphorus gettering of iron by screen-printed emitters in monocrystalline Czochralski silicon wafers

ABSTRACT In this paper, we demonstrate single‐sided screen‐printed emitters in thin monocrystalline Czochralski silicon (Cz‐Si) wafers with an improved gettering of iron compared with conventional double‐sided POCl3 emitters. The phosphorus dopant pastes used have to be chosen carefully to provide a sufficiently low emitter sheet resistance and to avoid iron contamination. The iron concentration is determined in a non‐destructive way from the minority carrier lifetime obtained by quasi‐steady‐state photoconductance measurements, down to levels not yet demonstrated for screen‐printed emitters. In addition, the well‐known metastable boron–oxygen complexes in Cz‐Si have been transferred into a stable state by light‐induced degradation prior to these measurements. Copyright © 2012 John Wiley & Sons, Ltd. We demonstrate single‐sided screen‐printed emitters in thin Cz‐Si wafers with an improved gettering of iron compared with conventional POCl3 emitters. The phosphorus dopant pastes used have to be chosen carefully to provide a sufficiently low emitter shunt resistance and to avoid iron contamination. The [Fe] is determined in a non‐destructive way from the minority carrier lifetime obtained by quasi‐steady‐state photoconductance measurements, down to levels not yet demonstrated for screen‐printed emitters. Metastable BSO2i complexes have been transferred into a stable state by light‐induced degradation prior to these measurements.