**2. Natural radiation at ground level**

310 Numerical Simulation – From Theory to Industry

reliability and dependability [1].

contaminants.

technological nodes.

constraint).

neutrons in avionics: the alpha particles generated from traces of radioactive contaminants in CMOS process or packaging materials [1,15]. As a consequence of these multiple sources of radiation, the accurate modeling and simulation of the SER of circuits at ground level is rather a complex task because one can clearly separate the contribution to SER of atmospheric particles (the external constraint) from the one due to natural alpha-particle emitters present as contaminants in circuit materials (the internal

Modeling and simulating the effects of ionizing radiation has long been used for better understanding the radiation effects on the operation of devices and circuits [16-19]. In the last two decades, due to substantial progress in simulation codes and computer performances which reduce computation times, simulation reached an increased interest. Due to its predictive capability, simulation offers the possibility to reduce radiation experiments and to test hypothetical devices or conditions, which are not feasible (or not easily measurable) by experiments. Physically-based numerical simulation at devicelevel presently becomes an indispensable tool for the analysis of new phenomena specific to short-channel devices and for the study of radiation effects in new device architectures for which experimental investigation is still limited [19]. In these cases, numerical simulation is an ideal investigation tool for providing physical insights and predicting the operation of future devices expected for the end of the microelectronic roadmap. Last but not least, the understanding of the soft error mechanisms in such devices and the prediction of their occurrence under a given radiation environment are of fundamental importance for certain applications requiring a very high level of

In this framework, this chapter describes in details a complete general purpose simulation platform we have developed these last years for the numerical evaluation of the sensitivity of advanced semiconductor memories (static RAMs) subjected to natural radiation at ground level. The physical modeling approach we developed as well as the object-oriented programming implementation are very general and can be used to simulate both external or internal radiation constraints, i.e. the bombardment of the memory circuit by heavy-ions, neutrons, protons, muons, etc. or the generation of alphaparticles inside the circuit materials due to the presence of traces of radioactive

The chapter is organized as follows. After introducing the natural radiation environment at ground level and the different types of radiation constraints in section 2 and the basic mechanisms of single-event effects on microelectronic devices in section 3, section 4 will present in details the different modules of our multi-scale and multiphysics numerical simulation chain, including some important precisions related to the modeling of the circuit architecture, the generation of particles mimicked a given radiation environment and the physical-based modeling of the circuit/cell electrical response. Finally, in section 5, we will illustrate various capabilities of our code to estimate the soft-error rate of different SRAM circuits representative of advanced As briefly stated in the introduction, natural radiation that causes soft error in digital circuits may come from various sources. At ground level, one can distinguish two major sources of radiation described in the following: i) the atmospheric radiation environment and ii) the telluric radiation sources,.
