Imprint lithography enabling ultra-low loss coaxial interconnects

Processing techniques have been demonstrated to fabricate a novel structure with smooth transitions, metallic shielding, and encapsulated air dielectric layers using sacrificial polymers and the three-dimensional patterning capabilities of imprint lithography. This innovative structure incorporates encapsulated air dielectrics with copper shielding. A semicircular stamp was fabricated to create the circular base of the coaxial transmission line using the reflow properties of solder, and imprinting the stamp produced smooth rounded terminations. Copper shielding was electroplated and a sacrificial photosensitive polycarbonate was patterned using a unique interaction with the copper. The polycarbonate was over-coated with a epoxycyclohexyl polyhedral oligomeric silsesquioxane (POSS) layer and then thermally decomposed to form an air cavity. A center conductor was patterned using photolithography and electro-deposition. The half-coaxial line was aligned with a sample with the top portion of the copper shielding and bonded in the imprinter to complete the structure. Imprint lithography also demonstrated the capability to planarize surfaces which simplified the buildup process, and complex structures were fabricated with a comparable number of registration steps to traditional transmission lines. The mechanical integrity of the air-clad transmission lines was also evaluated using nano-indentation.