Swirl defect investigation using temperature- and injection-dependent photoluminescence imaging

The swirl defect is observed in both n-type Czochralski (Cz) and non-contact crucible (NOC) Si wafers. It is postulated to be the outcome of oxygen precipitation during crystal growth and/or post-growth high temperature processes, specifically processes involving temperatures in the range of 800°C–1000°C. This defect is characterized by low lifetime ring-like regions that decrease the device performance. We employ a technique based on temperature- and injection-dependent photoluminescence imaging (TIDPLI) to characterize the swirl defect. We compare the calculated fingerprints of the defects responsible for the swirl pattern observed in both Cz and NOC-Si wafers to determine whether the swirls are caused by the same defect. We find significantly different defect fingerprints for the swirl defects in n-type Cz and NOC-Si. The Shockley-Read-Hall (SRH) description of the Cz-Si defects differ not much from the SRH description of intentionally grown oxygen precipitates, whereas the SRH parameters for the NOC-Si defects differ significantly. Identifying the limiting defect, allows us to suggest methods for its annihilation. We then successfully apply a rapid thermal annealing treatment to dissolve swirl defects in Cz-Si samples and homogenize the lifetime.