Mechanical stength of Czochralski silicon crystals with carbon concentrations from 1014 to 1016 cm−3

Using Czochralski-grown silicon crystals with carbon concentrations from 1014 to 1016 cm−3, we studied the influence of oxygen precipitates on the mechanical strength of silicon crystals. Reducing carbon concentration from 1016 to 1014 cm−3 suppressed oxygen precipitation and thus, improved the strength. Carbon concentration reduction from 1015 to 1014 cm−3 did not, however, decrease oxygen precipitation as dramatically as reduction from 1016 to 1015 cm−3. Carbon impurities below 1014 cm−3 no longer affect oxygen precipitation. Therefore, we conclude that reducing carbon concentration below 1014 cm−3 no longer improves the mechanical strength of silicon crystals.