Effect of oxygen and associated residual stresses on the mechanical properties of high growth rate Czochralski silicon

The mechanical properties of Czochralski silicon (Cz-Si) crystals grown in vacancy rich regimes with elevated axial oxygen concentrations ranging from ∼6 × 1017 to ∼12 × 1017 atoms/cm3 have been investigated using nano- and micro-indentation techniques. Both hardness and fracture toughness were found to decrease with increasing oxygen concentration, while major differences in mechanical properties were found between the central core and the edge of the high oxygen concentration wafers. Photoluminescence imaging and Nomarski optical microscopy of high-oxygen wafers revealed the presence of a ring and swirl-like distributions of micro defects, including oxidation induced stacking faults. Micro-Raman analysis was used to measure local residual stress profiles associated with these characteristic defects. These results provide a quantitative understanding of the influence of the oxygen content and the associated defects resulting from the sub-optimal growth regimes within the Cz-Si process.