Interface trap generation in MOS structures by high-energy electron irradiation

The changes of defect characteristics of MOS structures induced by irradiation with 23 MeV electrons are studied. The samples were irradiated for 30 or 120 s. The distributions of radiation induced interface traps, located at the Si/SiO2 interface obtained from capacitance-voltage (C-V) characteristics and decomposition of multi-frequency conductance-voltage (G-V) characteristics, are dominated by distinct defects, with different localized energy levels in the Si bandgap. The interface traps are related with Pb centers, with concentrations depending on irradiation time. The Pb1 concentration shows an order of magnitude increase as compared to the reference unirradiated sample, while Pb0 are found only after electron irradiation. The C-V characteristics indicate an increase of the positive oxide charge in SiO2 due to generation of E' defects. Defects in the Si bulk space charge region are also generated, which can be attributed to boron (V/B) and oxygen (V/O) vacancies complexes.