Degradation of electron irradiated MOS capacitors

We have investigated the degradation of MOS structure due to high energy el ectron irradiation as a function of radiation dose and gate bias applied du ring the irradiation. Devices have been characterized by current-voltage me asurements, in order to study charge accumulation also at the gate interfac e, Three types of oxide charge have been observed: the unstable positive ch arge, due to trapped holes induced by the electron irradiation; the negativ e charge in the oxide bulk, deriving from capture of electrons injected dur ing electrical measurements in radiation generated traps; and border traps, at both oxide interfaces. (C) 1999 Elsevier Science Ltd. All rights reserv ed.