Microscale Heat Conduction in Integrated Circuits and Their Constituent Films

Advances in the semiconductor technology have enabled steady, exponential im- provement in the performance of integrated circuits. Miniaturization allows the integration of a larger number of transistors with enhanced switching speed. Novel transistor structures and passivation materials diminish circuit delay by minimizing parasitic electrical capacitance. These advances, however, pose several challenges for the thermal engineering of integrated circuits. The low thermal conductivities of passivation layers result in large temperature rises and temperature gradient magni- tudes, which degrade electrical characteristics of transistors and reduce lifetimes of interconnects. As dimensions of transistors and interconnects decrease, the result- ing changes in current density and thermal capacitance make these elements more susceptible to failure during brief electrical overstress. This work develops a set of high-resolution measurement techniques which de- termine temperature fields in transistors and interconnects, as well as the thermal properties of their constituent films.
At the heart of these techniques is the thermore- flectance thermometry method, which is based on the temperature dependence of the reflectance of metals. Spatial resolution near 300 nm and temporal resolution near IOns are demonstrated by capturing transient temperature distributions in intercon- nects and silicon-on-insulator (SOl) high-voltage transistors. Analyses of transient temperature data obtained from interconnect structures yield thermal conductivities and volumetric heat capacities of thin films.