Thermally activated defect behaviors in nitrogen (N)-doped Czochralski silicon (Cz-Si) single crystals were investigated using deep level transient spectroscopy and quasi-steady-state photoconductance to confirm the crystals’ applicability in insulated gate bipolar transistors (IGBTs). The thermally activated defects, which were probably N-vacancy complexes and degraded the minority carrier lifetime, were detected with extremely low densities in N-doped Cz-Si compared with N-rich floating zone Si single crystals after heat treatments at 500 °C, resulting in a high remaining value of minority carrier lifetime. The difference was assumed to come from whether vacancies were released in the Si matrix during heat treatment. For the Cz-Si, vacancies were assumed to be strongly bound with oxygen atoms with concentrations of 1017 atoms cm−3. Therefore, vacancies were not released during heat treatment, resulting in low remaining N-vacancy complex densities. N-doped Cz-Si are potential materials for IGBTs because of their low densities from thermally activated defects.
Nitrogen-doped silicon wafers manufactured using the Czochralski technique (Cz-Si) with an oxygen concentration ([OI]) of 2.5-5.6 × 10 17 atoms cm −3 are heat treated to simulate the conventional and scaled manufacturing processes of insulated gate bipolar transistors (IGBTs). Subsequently, the oxygen precipitation, lifetime, and gate oxide integrity (GOI) of the Cz-Si wafers are evaluated. After the high-temperature heat treatment that simulates the conventional process, the lifetime of the Cz-Si with an [OI] of 5.6 × 10 17 atoms cm −3 only degrades slightly even when oxide precipitates are not detected. In contrast, after the lowtemperature heat treatment that simulates the scaled process, oxide precipitates are detected and the lifetime reduces substantially at an [OI] of 5.6 × 10 17 atoms cm −3 . The Cz-Si with [OI] values below 3.3 × 10 17 atoms cm −3 are considered suitable materials for IGBTs because no oxide precipitate is formed, and the lifetime is not degraded after high-and low-temperature heat treatments. Upon using GOI evaluation, the nitrogen-doped Cz-Si wafers are found to exhibit a breakdown voltage equal to that of an annealed Cz-Si wafer conventionally used for IGBTs. Therefore, nitrogen-doped Cz-Si wafers with [OI] below 3.3 × 10 17 atoms cm −3 are potential materials for conventional and scaled IGBTs.
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