APPLICATION NOTE
6
.PARAM DOSE = 0.0 ;initialization of total dose
.STEP PARAM DOSE LIST 0 1E5 1E6
.FUNC VTO_DOSE(DOSE) 1.65*(1 - 4.18E-6*DOSE + 2.76E-12*DOSE*DOSE)
.FUNC UO_DOSE(DOSE) 600.0*(1 - 5.00E-7*DOSE)
.MODEL NN2 NMOS ( VTO={VTO_DOSE(DOSE)} UO={UO_DOSE(DOSE)} )
The .STEP capability is used to determine the circuit performance as a function of total dose. Simulations are
performed at DOSE = 0.0 (pre-rad), 1E5, and 1E6 rads(Si). Note that the functional relationship between
the threshold voltage and total dose has been defined as a nonlinear function, in this case a second order
polynomial fit. The variation in mobility as a function of total dose has been assumed to be linear.
Figure 6: Circuit Design for Total Dose Effects
The following are the simulation results for total dose effects when DOSE=0 [GREEN] , DOSE=1E5 [RED],
and DOSE=1E6 [BLUE].
Figure 7: Simulation result when DOSE=0, 1E5, 1E6
