Direct Sputtered Copper Seed Layer Formation on Low Dielectric Resin to Reduce Transmission Loss

We developed a method to form a copper seed layer directly on resins with excellent dielectric properties using sputtering (referred to as the direct sputtering method). One of the key challenges to implementing 6G wireless communication systems that use millimeter waves is minimizing high-frequency transmission losses, as the transmission loss is affected by the dielectric (resin substrate) and the conductor (copper wiring) used to fabricate the transmission line. We compared our direct sputtering method for fabricating transmission circuits with the electroless copper plating method by evaluating the characteristics of their high-frequency transmission up to 100 GHz. Our direct sputtering method has several advantages over the electroless copper plating method, including a streamlined fabrication process for the transmission circuit. The direct sputtering method reduces the usage of chemicals and the high-frequency transmission loss in the transmission circuit. Thus, our direct sputtering method is beneficial to the fabrication of transmission circuits for 6G wireless communications.