imental key parameters, i.e. the temperature and time of the anneal. Furthermore, the rate limiting process is the O diffusion and the activation energy (2.54 eV) is compatible with the slope of Arrhenius plot (around 3 eV). To show that the model closely matches the temperature and time effects of post-oxidation anneal, we have calculated the corresponding voltage. Fig. 65 illustrates the Vot shift after 1 Mrad(SiO2) and the calculated voltage induced by out-diffusion as function of anneal temperature. The shape of the predicted curves is in agreement with the experimental data. Differences in magnitude could be explained by the three following considerations (i) the predicted voltage Voxy is calculated by considering only positive charge traps, (ii) the radiation induced positive charge are not related one to one to oxygen vacancy precursors, and (iii) the dose level of the experimental data is not sufficient to fill up the available defect precursors. Figure 65. Comparison between Experimental predicted and experimental threshold Predicted data : -11.2 voltage shift. -12.8 Furnace -14.4 -16.0 Anneal Temperature (C) 7. INTERFACE STATES The equations of interface state generation are still a subject of debate. Consequently, it is not the goal of this course to address much of this matter, and the interested reader may refer to preceding Short Courses [Dres-98], or to review books [Ma-89]. However, a brief review will be made and parallel with charge trapping will be suggested. III-76 CONSEQUENCES OF INTERFACE STATE BUILD-UP FOR VTN AND VTP "Interface states" are interpreted to first order as missing (dangling) bonds between the silicon and the SiO2. These charges are SO close to silicon (even belonging to the silicon in some sense) that they act as scattering centers for carriers moving in silicon (e.g. from source to drain). These states situated to the Si-SiO2 interface have energy levels situated in the forbidden band of the silicon, and the charge depends on the position of the surface potential with respect