Low cost 3D multilevel interconnect integration for RF and microwave applications

Abstract

This work presents a new and low cost multi-level 3D copper interconnect process for RF and microwave applications. This process extends 3D interconnect integration technologies from silicon to above-IC polymer. Therefore, 3D passive devices and multi-level interconnects can be integrated using a single electroplating step making the process suitable for 3D-MMIC integration. 3D interconnects are realized by patterning the SU-8 to specific locations to create the desired 3D shape. A 3D seed layer is deposited above the SU-8 and the substrate to insure 3D electroplating current flow. The BPN is used as a thick mold for copper electroplating with an aspect ratio as high as 16:1. An optimized electroplating process is later used to grow copper in a 3D technique, insuring transition between all metallic layers. Finally, high-Q (60 @ 6 GHz) power inductors have been designed and integrated above a 50 W RF power LDMOS device, using this process.