High-aspect-ratio through silicon vias (TSVs) for high-frequency application fabricated by magnetic assembly of gold-coated nickel wires

In this paper we demonstrate a novel manufacturing technology for high-aspect-ratio vertical interconnects for highfrequency applications. This novel approach is based on magnetic self-assembly of pre-fabricated nickel wires that are subsequently insulated with a thermosetting polymer. The high-frequency performance of the through silicon vias (TSVs) is enhanced by depositing a gold layer on the outer surface of the nickel wires and by reducing capacitive parasitics through a low-k polymer liner. As compared to conventional TSV designs, this novel concept offers a more compact design and a simpler, potentially more cost-effective manufacturing process. Moreover, this fabrication concept is very versatile and adaptable to many different applications such as interposer, MEMS, or millimeter wave applications. For evaluation purposes, coplanar waveguides (CPW) with incorporated TSV interconnections were fabricated and characterized. The experimental results reveal a high bandwidth from DC to 86 GHz and an insertion loss of less than 0.53 dB per single TSV interconnection for frequencies up to 75 GHz.