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Thermal-Aware CAD for Modern Integrated Circuits


Power density in modern integrated circuits (ICs) continues to increase at an alarming rate. In turn, larger power densities result in higher peak temperatures which can reduce chip reliability and further increase leakage power consumption. Thermal-aware CAD design is a method to combat these problems. However most existing thermal-aware CAD research has focused on thermal-aware floorplanning and placement. These thermal-aware floorplanners have several problems such as long execution times and being limited to only one method of reducing peak temperatures. In addition most thermal-aware CAD research has only focused on reducing chip peak temperatures and not other reliability concerns such as high interconnect temperatures, wire/C4 bump electromigration, and thermal-cyclic C4 bump failure.

This thesis proposes several new algorithms and methodologies that can be used to directly reduce high on chip temperatures and mitigate the reliability concerns caused by these high temperatures. Experimental results show that the proposed thermal-floorplanning moves based on whitespace utilization, coupled with a method of quickly evaluating temperature effects can reduce on chip-temperatures on average by 7K with only a modest 4.2% increase in wirelength and 1.12x increase in execution time. In addition, a method for cooptimizing floorplanning and C4 bump placement using a quadratic optimization process is shown to increase the lifetime of bumps from thermal-cyclic fatigue by 47x with only a modest 3% increase in HPWL wirelength. To combat bump electromigration, a single-bump redundancy technique based on Integer Linear Programming (ILP) is proposed, and shown to be able to reduce the number of redundant bumps to guarantee single-bump redundancy by 68% as compared to a naive bump placement approach. Finally, an algorithm to redistribute decoupling capacitance, is shown to be able to reduce interconnect temperatures by 12.5K on average and provide a 1.66x increase in electromigration lifetime

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