Vacuum assisted liquified metal (VALM) TSV filling method with superconductive material

A novel, simple, low-cost method for the void-free filling of high aspect ratio (HAR) through-silicon-vias (TSVs) is presented. For the first-time pure indium, a type-I superconductor metal, is used to fill HAR vias, 300 to 500 μm in depth and 50 to 100 μm in diameter. The low electrical resistivity achieved without sintering, its reproducibility and straightforward processing steps, and the short time required to fill large arrays of vias at wafer scale — all make this method one of the simplest and quickest options for filling HAR TSVs for MEMS 3D integration. Moreover, the low melting point (∼ 150 °C), malleability and superconductivity at 3.41 K make indium an interesting option in 3D interconnects for connecting quantum devices operating below 4 K.