Monolithic integration of 3-D electroplated microstructures with unlimited number of levels using planarization with a sacrificial metallic mold (PSMM)

A new monolithic integration method for 3-D electroplated microstructures of unlimited number of levels has been developed using unique planarization with a sacrificial metallic mold (PSMM). Contrary to the conventional electroplating mold of photoresist or polyimide, the sacrificial metallic mold (SMM) is used for multiple functions: a sacrificial layer, a planarization layer, and a seed layer for the next-level electroplating as well. We have successfully demonstrated various three-level metallic microstructures, such as levitated on-chip inductors, micro-bridges, micro-cantilevers, and micro-mirrors. The RF performance of the fabricated inductor has shown excellent results of 5 nH, Q-factor of 50 at 5 GHz on glass. This method is very simple, highly adaptable, and IC-compatible, so that it can be used as a versatile tool to integrate various 3-D metallic microstructures in multiple levels.