**Acknowledgements**

to SEU. A detailed study of the collected currents in this area has then been conducted. For this purpose, a specific ion impact location (shown in **Figure 11**, labeled "detailed impact" in the top left corner of node SL) has been fixed and the collected current waveform following the ion impact at this location has been systematically analyzed, as well as the voltage waveform of the two bistable nodes. As expected, this node SL collects most of the charge as it corresponds to the stricken drain. However, the fine analysis (not shown) of the different transient currents indicates that the nodes SLN, N1 and N2 collect later, by a diffusion mechanism, a small quantity of charge, which is high enough to keep the voltage of the SLN node at the low logic state and to prevent a latch upset. In order to validate this affirmation, we removed from the circuit netlist in a separate simulation batch the drains corresponding to nodes SLN, N1 and N2. In this case, since no charge is collected on the NMOS of the SLN node to counter-balance the feedback loop of the latch, the electrical potential of the SLN node

To conclude, this particular charge-sharing mechanism in the area of the top left corner of collecting node SL has been observed whatever the value of the LET in the range 1.8–60 MeV

A new computational method for the simulation of single event effects in integrated circuits has been presented. This approach is a Monte Carlo method based on a random-walk driftdiffusion algorithm that transports the radiation-induced charge, segmented into discrete charge packets, in the semiconductor regions of a given circuit architecture. Carrier diffusion is very well reproduced with the random-walk algorithm while the carrier "drift" component of the model perfectly captures the effects of the electric field developed in the space-charge region of the reversely biased collecting contact(s). The model has been fully derived in C++ using advanced structures to model device/circuit geometry, particle track and charge transport, collection, recombination and extraction. This approach has been dynamically coupled with an internal subroutine or an external circuit simulator to take into account spatial and temporal variations of the electric field in the vicinity of the collecting structure(s). Thus, complex architectures, such as flip-flops, can be easily modeled and charge-sharing mecha‐

This chapter mainly focused on the model implementation and the way to solve the circuit response in the time domain, taking into account the circuit feedback on the charge collection process. Four simulation test cases have been explored and compared to radiation experiments or TCAD simulations in order to validate the proposed model. These test cases show good quantitative agreement between measurements and simulated data over a large range of LETs

not self-consistent with the electrostatic potential (in other words, Poisson's equation is not solved during the transient computation) and does not take into account the possible interac‐

/mg and structure complexity. This first implementation remains therefore

/mg, demonstrating the capability of the RWDD approach to treat such complex circuit

increases and an upset occurs.

134 Modeling and Simulation in Engineering Sciences

response to single events.

nisms are accurately simulated.

up to 60 MeV.cm2

**6. Conclusion**

cm2

This work is conjointly supported by France's General Directorates DGA and DGE, under convention #132906128 "EVEREST" (Evaluation of the soft error rate of FD-SOI technologies for strategic applications).
