Phosphorous gettering of cast multicrystalline silicon wafers from different positions of the ingot

The electrical properties of cast multicrystalline wafers cut from different positions of the ingot were studied by microwave photo conductive decay(μ-PCD) before and after phosphorous gettering treatment at 870℃ for 40 minutes.The minority-carrier lifetime of all wafers increased noticeably after phosphorous gettering.Moreover,the gettering effect of the wafers from the top of the ingot was more obvious than that from the bottom.It was found that a high concentration of oxygen existed at the bottom of the ingot,which was due to the segregation effect.The results showed that the gettering performance of multicrystalline silicon not only depended on the distribution and state of transitional metals but also was influenced by the oxygen concentration.