Analyses of the radiation-caused characteristics change in SOI MOSFETs using field shield isolation

Reliability against radiation is an important issue in silicon on insulator metal oxide semiconductor field effect transistors (SOI MOSFETs) used in s atellites and nuclear power plants and so forth which are severely exposed to radiation. Radiation-caused characteristic change related to the isolati on-edge in an irradiated environment was analyzed on SOI MOSFETs. Moreover short channel effects for an irradiated environment were investigated by si mulations. It was revealed that the leakage current which was observed in l ocal oxidation of silicon (LOCOS) isolated SOI MOSFETs was successfully sup pressed by using field shield isolation. Simulated potential indicated that the potential rise at the LOGOS edge can not be seen in the case of field shield isolation edge which does not have physical isolation. Also it was f ound that the threshold voltage shift caused by radiation in short channel regime is severer than that in long channel regime. In transistors with a c hannel length of 0.18 mu m, a potential rise of the body region by radiatio n-induced trapped holes can be seen in comparison with that of 1.0 mu m. As a result, we must consider these effects for designing deep submicron devi ces used in an irradiated environment.