CHALLENGES AND POTENTIAL SOLUTIONS

FOR DECADES, DIGITAL INTEGRATED circuits (ICs) have benefited from the relentless progress predicted by Moore’s Law. With each new technology generation, ICs become denser, faster, and cheaper. However, with increasing system integration, as well as aggressive technology scaling, IC thermal issues now stand in the way of improved IC performance. Many of us may have watched a video from called What happens when the CPU cooler is removed? This two-minute video clip shows the effect of removing a heatsink from a running 1,400 MHz AMD Athlon processor: the whole system crashes, the CPU temperature shoots up to 698 ◦ F, and smoke starts coming out of the chip within a few seconds. Today’s microprocessors can get extremely hot. IC temperature is a strong function of IC power density. With each technology generation, the integration density of semiconductor devices doubles. As a result of reduction in both device feature size and supply voltage, the power consumption of each transistor decreases. However, increasing transistor counts and aggressive frequency scaling result in a significant increase in chip-power density, hence temperature. Increasing chip temperature has significant impact on other design metrics including reliability, performance, cost, and power consumption. Circuit reliability depends exponentially upon operating temperature. When temperature increases, major reliability issues, such as electromigration (which affects metal wires) and time-dependent dielectric breakdown (which affects transistors), become more important. Currently, temperature effects account for over 50% of electronic failures. IC temperature also affects circuit speed. Reduction of charge carrier mobility in