الفهرس 
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Abstract
Progress in electronic circuits is marked by a continuous decrease in transistor size in order to achieve more functionality while keeping the same size, or even reducing it, as well as higher operating frequencies and hence faster devices. The continuous decrease in transistor feature size will inevitably increase the importance of thermal effects. In fact, the heat dissipated per transistor per cycle only slightly decreases when the size decreases. The heat power density, however, rapidly increases due to both the increase in the number of transistors per unit area as well as the increase of the number of cycles per second. High level of heat dissipation will give rise to important Electrothermal coupling that needs to be modeled for adequate design of modern electronic devices. To cope with this situation, it is necessary to take into account the transistor?s thermal characteristics while considering its electrical behavior. The latter will in turn influence the rate of heat dissipation. Hence, we need to perform coupled Electrothermal simulations. Electrothermal simulations of MOSFET (MetalOxideSilicon Field Effect Transistor) having channel lengths in the submicron range are performed in this work at two levels, to satisfy different needs. The first one aim at extracting an equivalent thermal network of a single transistor composed of a few numbers of thermal resistances and capacitances, the socalled compact thermal model. This compact model is needed for the analysis and design of circuits composed of millions of transistors. Thermal and electrical phenomena are coupled. However, the analysis is simplified by assuming that electrical properties are function of the average temperature inside each transistor, and not the detailed temperature field. This allows the use of a classic public domain simulator of electronic devices (MINIMOS) together with a solver of the heat conduction equation. Iterations are conducted manually between both tools (electrical and thermal simulators) until convergence. Both static and dynamic effects predicted by the model are compared with existing experimental results. On the past, Compact model for Transistor level contained only one thermal resistance, and one thermal capacitance. Hence, it was not accurate, and unable to accommodate arbitrary boundary conditions. The simplicity of the proposed model will make Electrothermal simulations at the circuit level accessible, and hence will improve considerably circuit design. The compact model also shows that transient effects inside a single transistor could be modeled by a small set of time constants. Some of them are indeed comparable to electrical time constants, contrary to the common belief. The second approach aims at understanding the mechanisms by which the temperature field influences electrical phenomena. A tool is built in this work that is dedicated to the detailed Electrothermal analysis of MOSFET transistor characteristic. It contains both an electrical and a thermal simulator that are intimately coupled. A coupled Electrothermal simulator at the device level was constructed for MOS transistors. It included many effects, in particular the Seebeck effect, which was suspected to have an influence, although no quantitative analysis was done yet. The results of the present simulator did not show a noticeable influence of the Seebeck effect on the characteristics of a MOSFET transistor, and hence its effect can be neglected in the studied range. Performance degradation resulting from thermal effects mainly originated from temperature dependence of the mobility. All electrical characteristics (electron and hole mobilities and diffusivities as well as recombination, generation, intrinsic ionization and thermoelectric power) are function of the local temperature. It allows the study of new phenomena inside the transistor including the effect of temperature gradient on the electric current induced by the Seebeck effect, as well as Joule and Thomson heats.