Thermal Simulation of Liquid-Cooled Integrated Circuits

Growing demands for increased functionality in consumer electronics and for information technology-enabled services in various sectors have resulted in the rise of high-performance multiprocessor system-on-chips (MPSoCs) and three-dimensionally stacked integrated circuits (3D ICs), that are deployed in various electronic devices and data centers to cope with these demands. This, in turn, has resulted in an alarming rise in electronic heat dissipation that now matches the levels typically encountered in nuclear reactors. On a small scale, the increased heat flux in ICs undermines the thermal reliability and lifetimes of these devices. On a large scale, it dramatically increases the cooling costs and the corresponding energy expenditure in data centers, thus escalating their carbon footprint globally to equal that of the airline industry, according to recent reports. Conventional copper-based air-cooled heat sinks and thermal packages are increasingly falling short in addressing these problems. Hence, advanced thermal packaging based on single- and two-phase liquid cooling of electronics have been recently proposed to cool integrated circuits to safe operating temperatures in a cost-effective manner. While possessing desirable properties compared to conventional heat sinks such as increased cooling capacity and energy-efficiency, liquid cooling of ICs does present various design challenges such as cost of technology migration, the design of micro-scale channels on silicon dies, implementation of electrical isolation and safe delivery of the coolant to the thermal package, optimization of electronic performance vis a vis cooling energy expenditure and structural reliability of the circuits. Electronic design automation (EDA) tools are needed during early stages of the design to evaluate these aspects, explore vast design spaces, develop control and management policies, reduce time-to-market, and minimize manufacturing and operating costs. At the heart of these tools is a fast compact thermal modeling method that can simulate the temperatures and cooling energies accurately for liquid-cooled ICs, in order to enable quick design space explorations at an early stage. In this thesis, compact thermal models for 2D/3D ICs are proposed to address this need. A compact thermal model for ICs with single-phase liquid cooling called 3D-ICE, a semi-analytical thermal model for the optimized design of liquid-cooled ICs and a compact thermal model for ICs with two-phase cooling called STEAM are proposed. The accuracy of these thermal models are validated against temperature measurements from real IC test stacks. In addition, these models are demonstrated to be orders of magnitude faster than conventional fine-grained simulators. Finally, two methods for accelerating thermal simulation are proposed to enhance the applicability of these methods in the early-stage design of 2D/3D ICs and MPSoCs with liquid cooling and other advanced thermal packages.