Study of Nanowire-Based Integrated via Technology for CMOS Application in Millimeter-Wave Frequencies

This work shows a novel integrated via structure based on 1.2- $\mu \text{m}$ thick copper nanowires (NWs) for use in CMOS applications at millimeter-wave frequencies. Coplanar waveguide (CPW) lines are fabricated on a 5000- $\Omega $ -cm high-resistivity silicon wafer and connected by NW vias that are grown in integrated anodized alumina oxide (AAO). The AAO layer is fabricated by anodizing an evaporated aluminum layer onto the silicon wafer. This cointegrated technology has 0.095-dB insertion loss for 0.3-mm long circuits with two vias at 40 GHz. The results are promising with an estimated loss per via of approximately 0.0275 dB. The fabricated structure shows great performance agreement with its reference test circuits of similar length. The design comparisons of circuits with different via dimensions and positions show that the shorter the via length, the wider the via width; and placing the via on the CPW ground plane closer to the signal line provides better performance.