AN ULTRASENSITIVE METHOD TO REVEAL DEFECTS THAT DEGRADE THE LOCALIZED RECOMBINATION LIFETIME OF THE NEAR SURFACE REGION OF BULK SI AND THIN EPILAYERS

摘要

A new wafer mapping technique based on room temperature photoluminescence has been successfully applied to characterize defects in the surface region of Si wafers. Analysis of epilayer samples grown on defective substrates has shown that the depth of detection for SiO_x is between 0-1 μm. On comparison with EBIC measurements it is possible to detect defects controlled by shallow recombination levels as well as those controlled by deep levels. Images recorded from wafers containing grown-in microdefects show that the effective defect area observed for the individual defect increase as the crystal growth rate is reduced The larger defect area is speculated to be related to the presence of dislocation loops present in the sample with the slower growth rate. Si wafers containing 10~8 cm-3 SiO_x precipitates were measured before and after Fe contamination. The defect density, defect contrast and defect area all increased after contamination. It is suggested that the observed defect size is related to the a chemical interaction of impurities with the SiO_x precipitates rather than strain related.