Ultra-high dose effects and junction leakage current in CMOS technologies for analog applications

The electronics circuit has become a central and essential tool in our modern society. It invested the objects of everyday life, and we directly or indirectly use dozens of them every day without even realizing it. Since the introduction of the transistor as we know it at the end of the 40's, electronics circuits have continued to improve and specialize to become more efficient in every application. Today, the most widely used technology for designing these electronics is the MOS (Metal-Oxide-Semiconductor) technology.Therefore, it is pretty natural to find MOS electronics circuits in all the space and nuclear applications where they perform a multitude of essential functions. However, these environments have the particularity to have a high density of radiation which degrades the electronic components. These degradations are all the more problematic as the circuits exposed to such environments are often supposed to provide excellent performance and high reliability. In order to guarantee the proper functioning of these circuits, it is, therefore, necessary to study the effects of these environments on the MOS electronics performances.Moreover, and this is the motivation for this thesis, these applications in radiative environments are booming. Not only is the demand for such circuits increasing, but the maximum radiation dose received by the electronics over its lifetime is expected to exceed unprecedented levels. These new doses and their effects on electronics are still poorly investigated, and the study of these effects is, therefore, essential to allow the future use of electronics in these environments, whether in nuclear, space or elsewhere.In particular, this thesis studies the effects of high doses of ionizing radiation on MOS transistors (MOSFETs) for analog circuits, circuits that are often more exposed than others. All this with the aim of, on the one hand, being able to anticipate these effects better and, on the other hand, counteract them when possible.The thesis first deals with the degradation during irradiation of MOSFET parameters such as the maximum current, the threshold voltage, or the leakage currents. In particular, the effects of voltage, oxide thickness, design, and size of the transistor are investigated. The results highlight the decisive role of the voltages during the irradiations on the type of defects created, particularly in the gate, along with the appearance of a short channel effect (RISCE) in a larger technology node than previously observed. Finally, this study of the parameters of MOSFETs highlights the significant increase of the generation current after high ionizing doses in the pn-junctions of the transistor. An in-depth analysis of this current follows.In a second step, the thesis studies the phenomenon of RTS (Random Telegraph Signal) in this pn-junction leakage current of the transistors. For this purpose, a test structure capable of measuring tens of thousands of leakage currents in parallel is introduced. Thanks to this structure, the RTS is statistically studied before and after irradiations. The results, in agreement with atomic-scale simulations, support the hypothesis of metastable defects as the origin of the RTS phenomenon in leaky junctions. (author)