Modification of Minority Carrier Lifetime in B-Doped Photovoltaic Grade Si Wafers Due to Surface Defects Produced by Mechanical Damage

Abstract

After oxidation treatment at , three kinds of structural defects were observed on the surface of the silicon wafer previously lapped with diamond abrasive slurry. One of them was oxidation-induced stacking faults (OISF) whose density increased with the decreasing size of the abrasive particles. Etch pits probably caused by multiple dislocation loops were observed on the surface ground with large abrasive particles. These defects were not observed on the silicon surface ground with finer abrasive particles. Instead, small etch pits caused by defects growing from the OISF were observed. All of these structural defects were not observed to form if the oxidation was performed at . Measurement of minority carrier lifetime of the silicon wafers having structural defects on the surface showed that the formation of these structural defects may not be the necessary condition for effective gettering. Rather than these structural defects, a strained layer, which was expected to form by oxidation treatment at low temperatures like , might be the better surface condition for effective extrinsic gettering in silicon crystal.