(Invited) Effect of Low Carbon Concentration on Bulk Lifetime of Silicon Crystal

Reducing the electric loss of power semiconductor devices such as insulated-gate bipolar transistors (IGBTs) is necessary for saving energy and reducing fuel consumption. An essential factor for achieving low-loss IGBTs is increasing the bulk lifetime of the silicon crystals. To achieve a longer bulk lifetime, we reduced the carbon concentration in magnetic-field-applied Czochralski (MCZ) silicon. We investigated the bulk lifetime of MCZ silicon with ultralow-carbon-concentration and floating-zone (FZ) silicon to clarify the impact of carbon impurities on the bulk lifetime. The bulk lifetime was measured using a direct-current photoconductive decay method designated by ASTM F28-75. The bulk lifetime of MCZ silicon drastically increased with decreasing carbon concentration. MCZ silicon crystals with a carbon concentration less than 1.0 × 1015 atoms/cm3 exhibited a longer bulk lifetime than FZ silicon crystals. We demonstrated that carbon-concentration reduction is crucial for increasing the bulk lifetime of MCZ silicon crystals.