Three-Dimensional Solenoids Realized via High-Density Deep Coil Stacking for MEMS Application

摘要

Three-dimensional solenoids have been developed and demonstrated for the first time in stacking of through-silicon via chips. High-density microcoils ($sim!!hbox{20}hbox{-}mu hbox{m}$ width, $sim!!hbox{10}hbox{-}muhbox{m}$ space, and $sim!!hbox{90}hbox{-}muhbox{m}$ depth with 24 turns) were completely filled with Cu. Eight high-density microcoil chips were stacked using a conductive adhesive. The inductance of the eight stacked high-density microcoil chips is measured to be $sim!!hbox{30} muhbox{H}$ at 0.9 MHz, and the maximum magnetic field reaches to $sim$0.67 mT, as characterized by a magnetic field detector $sim$2 mm above the cavity center of the coils. The eight stacked high-density microcoil chips achieved 66-h operation under continuous current ( $sim$0.2 A) stress testing without failure. Two microcoil chips stacked using solder also completed 1000 thermal cycles ($-hbox{40} ^{circ} hbox{C}$ to 125 $^{circ}hbox{C}$) successfully with merely $sim$3.7% resistance change.