Stability of trapped electrons in SiO2

Thermally stimulated current and capacitance voltage methods are used to investigate the thermal stability of trapped electrons associated with radiation-induced trapped positive charge in metaloxide-semiconductor capacitors. The density of deeply trapped electrons in radiation-hardened 45 nm oxides exceeds that of shallow electrons by a factor of similar to 3 after radiation exposure, and by up to a factor of 10 or more during biased annealing. Shallow electron traps anneal faster than deep traps, and exhibit response that is qualitatively consistent with existing models of compensated E-gamma' centers in SiO2. Deeper traps may be part of a different dipole complex, and/or have shifted energy levels that inhibit charge exchange with the Si. (C) 1999 American Institute of Physics. [S0003-6951(99)01220-6].