Abstract
Vacancy-type defects in HfSiON high-k films were studied by the S-parameter of positron annihilation. In the as-deposited HfSiON films, high-density oxygen vacancies (VOs) induced a large built-in electric field (Ebuilt-in) toward Si substrate. It was observed that the thermal positrons diffused from HfSiON films to Si substrate by the driving of the Ebuilt-in. Because HfSiON has a small characteristic S-parameter and Si substrate has a large characteristic S-parameter, the observed S-parameter was indirectly increased by the VOs. When most of VOs were compensated by annealing of the samples in nitrogen or oxygen ambient, the Ebuilt-in was much reduced not to effectively drive thermal positrons from HfSiON to Si. Then the S-parameter was observed to be smaller.
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