dose variation with manufacturing lots difference between N and P type transistors The basic frame of understanding is that "something" is building up under the influence of dose. This "something" may takes several forms according to the type of the device, the time scale at which it is considered and the way the device has been manufactured, and therefore a comprehensive modeling is required to master all the aspects. This course will only introduce certain aspects, some others being beyond the scope, or some question being too much a matter of research or debate to be addressed in a course. The similar beginnings at low dose is attributed to a common phenomenon to N and P-type, whereas the difference at larger dose is attributed to another different phenomenon which can produce similar effects in N and P, but with sign opposed. More specifically, the variation of threshold voltage is divided into two components named as follows: VIN = VOIN + VitN THRESHOLD VOLTAGE SHIFT DOSE EFFECTS TURN-AROUND POINT N MOS TRANSISTOR POSITIVE SHIFT 2N4351-Motorola NEGATIVE SHIFT P MOS TRANSISTOR 3N164-Siliconix SATURATION REGION LINEAR REGION => TWO COMPONENTS IN THRESHOLD VOLTAGE 0 100 1000 Dose (krad) BIAS DURING IRRADIATION Vgs=Vds=0 Figure 8. Interpretation of threshold voltage shifts as the sum of two components. Figure 8 displays the typical negative threshold voltage variation for PMOS, and the firstly negative then positive variation for NMOS. This last phenomenon is due to the fact that VOT saturates, while VIT presents much weaker (or no) saturation. The position from the point of III-11 turn-around according to laws and parameters, as well as the thickness of the oxide and electric field (bias) has to be analyzed. In the following, we first address the common component to the two types of transistors. 3.1. CONSEQUENCES FOR TRANSISTORS AND CIRCUITS For transistors of N type, consequences of negative threshold voltage values, or positive but close to zero (<0.5 V), are an increase of the NMOS leakage current. At higher