chapter). III-78 irradiation Oxide Silicon oxygen vacancy Field-Assisted Drift electrons holes electrons E' centers polarons Field-Assisted Drift excitons other reactions Si-OH H-SIE Fleld-INDEPENDENT Drift recombination (Surface) (Bulk) Field-Assisted Drift Figure 67. Diagram of electronic and chemical processes induced by radiations in MOS structures of SiO2 and its interface with silicon [Gris-88]. Hydrogen ions liberated in the oxide during the irradiation can migrate to the Si/SiO2 interface, where they can react and form interface traps. These two types of defects, traps with positive charge in the oxide and interface traps, cause degradation of electrical parameters of elementary transistors. As a summary, a parallel is drawn in table 8 between phenomena where carriers are electrical charges only and those where the agent is a chemical species: Radiation Fluxes Absorbed Energy / Dose Profile Free Carriers Yield Function Y(E) Charge Separation, Photocurrent at Electrodes CSPE Charge Imbalance Imbalanced Charge Branch Unstable Chemical Species Branch Drift, Self-Trapping, Transient Carrier Localization De-Trapping DSTTDT at Weak Bond of Foreign Atoms Shallow/Deep Trapping in bulk SiO2 Thermal Detrapping and Drift (i.e. Si-H, Si-Si, Si-OH, ...) Tunneling Neutralisation X-Species Release Carrier Dipoles (e.g. X = H, or H+, or other) Border Traps Effects X Drift Swiched Oxide-Trapped Charge (possibly polaronic if X=H+) X-X' Reaction at SiO2/Si Interface XX'RI Oxide-Trapped Branch Interface-Trapped Branch oxide traps interface states slow exchange with silicon or quasi-stable charge reversible and fast exchange with silicon Table 8. Parallel between trapped charge and interface-states build-up. Two chains of radiation processes can exist in SiO2, having in common the transport and transformation of a species X released by radiation in the volume of SiO2, then interacting, mostly transformed (or trapped) at or near an interface to produce the resulting degradation III-79 expressed by an electrically-active specie