Quality evaluation and improvement of iron-doped electromagnetic multycrystalline silicon wafers

The effect of iron doping in electromagnetic cast (EMC) Si wafers on minority carrier recombination lifetime has been extensively investigated by means of microwave detected photo-conductivity decay (μ-PCD) and surface photo-voltage (SPV) to discriminate impurities and defects for the lower crystal quality. Optical and thermal activations of doped iron are investigated to study the difference between the two techniques in obtaining iron concentration. Minority carrier lifetimes increase or decrease after activation due to the different optical injection levels of both the SPV and μ-PCD techniques. No noticeable effect of chemical passivation in obtained iron concentration is observed. Boron and phosphorus gettering and hydrogen passivation techniques are applied to improve minority carrier recombination lifetime. As a result, the crystal quality of the EMC Si wafers depends on defect centers rather than on iron impurities.