Swirl Defect Investigation Using Temperature- and Injection-Dependent Photoluminescence Imaging

Oxygen is the most common impurity present in silicon wafers. High temperature device fabrication processes lead to oxygen precipitate nucleation and growth. These precipitates, with their internal gettering ability of metal impurities, are thought to be the reason behind the swirl defect. We characterize the swirl defect observed in both Czochralski (Cz) and non-contact crucible (NOC) silicon wafers using temperature- and injection-dependent photoluminescence imaging (TIDPLI). We generate swirl defects by subjecting the wafers to phosphorus diffusion gettering at 860°C followed by thermal oxidation at 1000°C. We use TIDPLI to compute the spatially resolved SRH lifetime strictly due to the swirl defect. This allows the fitting of two independent defects and the calculation of their parameters 1 and 2. We compare the resulting defect parameters in both Cz and NOC silicon wafers to determine whether the swirl pattern in both types of wafers originates from the same defect. Our results for the Cz wafers differ from defect parameters reported previously in the literature for Cz wafers with intentionally grown oxide precipitates. This might be an indication of a different oxide precipitate morphology in the swirl patterns. Also, we successfully apply a rapid thermal annealing treatment, often called tabula rasa, to annihilate the swirl defect at a temperature of 1080°C. We explain the results by the dissolution of the oxide precipitates responsible for the swirl defect, restoring a homogeneous lifetime across the wafer free of swirl defects.