Theoretical study of radiation sensitivity of CMOS/SOI technologies using 3D Monte Carlo simulation

We present a theoretical study of the behavior of CMOS inverters and static memory cells struck by an ionizing particle. Interaction of an energetic particle with matter results in generating electron-hole pairs. The main features of the created carriers are their high densities, their high energies (a few eV) and their very localized creation zone. To take into account the three-dimensional radiations features we have extended the particle Monte Carlo model of the Institut d'Electronique Fondamentale to three-dimensional device simulations in geometric space. To save computer memory and CPU time, we replaced the non-irradiated transistor by an electrical model which parameters were obtained from preliminary Monte Carlo simulations of each single transistor. Simulations of inverter in CMOS/SOI technology with channel tie (contact) show that irradiation of the off-state transistors induces a transient change of the output logic state whereas irradiation of the on-state transistors has weak effects on the output voltage. For this technology, a linear energy transfer (LET) of about 15 MeV.cm².mg^-1 induces a logical state swinging of a static memory cell, which is compatible with experimental results. We have then studied the radiation effects on an inverter in fully-depleted SOI technology. Although fully-depleted technology presents active zones with a reduced volume, the excess minority carriers resulting from irradiation remain trapped in the transistor because of the lack of channel tie. In an inverter it results in a change of the logic state which lasts for the minority carrier lifetime. In a memory cell this single event upset may induce a loss of information. (author)