Investigations on the Pumping Behaviors of Copper Filler in Through-Silicon-vias (TSV)

In this paper, the pumping behaviors of copper filler from TSV were systematically investigated. First, in-situ observation of copper pumping from TSV was conducted in scanning electronic microscope (SEM), the pumping height of copper filler and its evolution with time and temperature was recorded, it is found that the pumping rate increase with temperature and the maximum pumping height reached 12 µm. Second, the micro-mechanism of copper pumping was experimentally investigated with the aid of acoustic emission (AE) system, it was found that mass diffusion controlled creep deformation of interface should be the main mechanism copper pumping. Based on these experimental results and some reasonable assumptions, a theoretical model and its corresponding calculation algorithm were developed. After comparison with the known results about shear stress distribution along the TSV interface, the verified model was applied to predict the pumping height of TSV and qualitative consistence was obtained, possible sources of error were analyzed.