92c]. This structure has been irradiated to a dose of 20 krad(SiO2) at +30V. Then a TSC experiment has been simulated on the irradiated structure (TSC bias -100V, ramp rate 0.1 °C/s). The comparison of experimental and simulated ITSC is plotted in fig. 55 as a function of temperature. III-67 350 nm, 20 krad@+30V Experimental TSC Bias 100V Simulation Temperature (C) Figure 55. Simulated TSC on a 350 nm soft oxide MOS capacitor (TSC bias -100V), irradiated to 20 krad (irradiation bias +30V) [Pail-98]. A simulation code has been developed to calculate charge transport, trapping and detrapping properties in MOS structures. The results presented fit very well with experimental data on thermally stimulated currents. Further improvements of the models, such as tunnel assisted trapping phenomena for example, will enable the description of charge compensation effects in MOS structures. It will then be possible to predict the evolution of a component under its real operating conditions (i.e. for example long time irradiation at a low dose rate and variable temperature for space applications). This set of equations has been implemented in 1-D code [Cirba-95, Pail-98] under the name "TRAPPOXR v.3-CEA/CEM), and used for MOS purposes [Pail-98] and, with modification, for bipolar modeling [Grav-98]. It is presently implemented in 3-D under the name RAD- TRAPPOX TM v.5-CEA/ISE (see Appendix). From the experimental viewpoint, work is underway to get use of isochronal annealing along with TSC SO as to obtain energy profiles [Chab-97a, Chab-97b, Saig-97, Flee-98, Flam-99] under specified circumstances. 6. TRAPPING AND LINKS WITH THE MANUFACTURING PROCESS 6.1. DEFECTS The trapping is described as the capture of a hole on a pre-existing defect called a precursor. The simplest example of a mechanism of this type is the breaking of a steady bond by the trapping of one hole. III-68 Figure 56. An example of trap to hole: representation of the trapping of a positive charge on a oxygen vacancy bond The oxide is generally described as an am