Silicon Micropin-Fin Heat Sink With Integrated TSVs for 3-D ICs: Tradeoff Analysis and Experimental Testing

Abstract

Microfluidic cooling is proposed as a solution to reject heat from a 3-D IC stack of high power chips. However, the integration of interlayer microfluidic cooling in 3-D ICs inevitably increases wafer thickness and thus presents possible challenges for through-silicon via (TSV) integration. This paper discusses the thermal and electrical co-design of a microfluidic heat sink compatible with TSV technology. A TSV-compatible micropin-fin heat sink (MPFHS) with a height of 200 μm, a micropin-fin diameter of 150 μm, and a pitch of 225 μm is fabricated. The fabricated MPFHS is experimentally shown to maintain the chip junction temperature at a power density for a flow rate of 70 mL/min. The thermal results are benchmarked with an air-cooled heat sink and a chip junction temperature reduction of is observed. A 3 × 3 array of TSVs, each with a diameter of 10 μm and a height of 178 μm (18:1 aspect ratio), is integrated into each micropin-fin. This results in a TSV density of 17424 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> in the microfluidic heat sinks. Using four-point probing, the measured resistance of TSVs is 36.5±1.5 mΩ.