Integrated Waveguides in Nanoporous Alumina Membrane for Millimeter-Wave Interposer

The integration of rectangular waveguides inside a nanoporous alumina membrane is proposed in this letter. The horizontal copper plates are realized by a photolithography process while the vertical connections are made of copper nanowires selectively grown inside the nanopores. The lateral wall position can, therefore, be freely adjusted. Waveguides in the V-band (50-75 GHz) and the W-band (75-110 GHz) were manufactured in a 50-μm-thick membrane. For the measurement purpose, wideband transitions from a grounded coplanar waveguide to the waveguide were designed. The measured performance validates the propagation of guided waves with an attenuation constant of about 0.5-0.8 dB/mm in the operating bands, opening the way for the design of functionalized millimeter-wave alumina interposers.