Carbon nanotube bumps for thermal and electric conduction in transistor

The continuous miniaturization of semiconductor chips has rapidly improved the performance of semiconductor products. However, thermal issues that affect semiconductor chips are becoming more serious. For example, heat transfer has become a very serious problem in the CPUs of personal computers; high-frequency high-power amplifiers (HPAs) of mobile communication systems; and power control units of hybrid-car motors. To solve this problem, Fujitsu has been developing semiconductor heat sinks that exploit the high thermal conductivity of carbon nanotubes (CNTs). This paper describes the CNT bumps we have recently developed for transferring heat and electrically connecting the source, gate, and drain of the high-power, flip-chip amplifiers of mobile communication base stations. CNT bumps can be used to achieve high gain and high thermal conductivity in high-frequency HPAs. This paper introduces some recent developments in CNT bump technology.