can easily be used. It gives the following set of representation (fig 19.). The two curves a and b refer to the response at low dose (linear) and at high dose (saturation), respectively [Lera-89a]. Large dose +1.00 /mutp= 1E-12 1E-12 1E-12 Weak dose +0.80 +0.70 $0.60 +0.50 Figure 19. Analytical modeling of +0.40 V ot at low and high dose. V ot versus EG +0.30 (MV/cm). +0.20 Case of a 65 nm oxide +0.10 and pt = pr=10-12 cm2 -0.00 -2.000 -1.200 -0.400 0.400 1,200 2. .000E +6 betaf6 10-12-1987 22:26:09 3.12. PRACTICAL APPLICATIONS Due to the complexity of the phenomena occurring during the generation, transport and trapping of charges in an irradiated oxide, simple analytical expressions can only be obtained when broad simplifying assumptions are made. The equations derived from these models are then only usable in the experimental context that satisfies the series of assumptions made. To simplify the interpretation of experimental results even further, we attempt next to schematize the behavior of some typical oxides. This will give us a tool to rapidly identify specific trends by the simple observation of some measured electrical characteristics. 3.12.1. ELECTRICAL MEASUREMENT TECHNIQUES Before beginning to discuss and interpret experimental results, let us briefly recall some of the most common measurement techniques used to electrically characterize defects in MOS devices. In practical applications, the experimental structure being tested is either a MOS capacitor or a MOS transistor. In the case of a MOS capacitor, the technique consists in recording the capacitance-voltage curve (C-V curve), either using a small AC signal superimposed on a DC voltage ramp (high or low frequency C-V), or using a quasi static C-V technique. Fig. 20 shows typical high frequency (1MHz) C-V curves obtained on a p-substrate MOS capacitor, before and after irradiation at a dose of 10 Mrad(SiO2). The dashed lines in fig. 20 show the position of the flatband (Cfb) and midgap (Cmg) capacitances, defined respectively as the capacitance v