Two-phase microchannel cooling is one of the most promising thermal-management technologies for future high-power IC chips. Understanding the boiling process and the two-phase-flow behavior in microchannels is the key to successful implementation of a microchannel heat sink. This book focuses on the phase-change phenomena and the heat transfer in sub-150 nm diameter silicon microchannels, with emphasis on thermal measurement and modeling, and the impact of small dimensions on two-phase flow regimes. Scientists and engineers tackling thermal and MEMS problems will find the discussion in this book inspiring for their future design of microscale heat transfer experiments. This book will also contribute to the study of two-phase microchannel flows by providing extensive experimental data which are otherwise difficult to access.

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.

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.