High Quality Factor Copper Inductors on Wafer-Level Quartz Package for RF MEMS Applications

The paper proposes and validates a new doubly functional quartz wafer-level package concept for MEMS devices. In addition to the mechanical and environment protection, thick-Cu high-Q inductors for RF applications are made within the package processing. A double-side processing of a quartz wafer is reported. While the top side of the quartz is used to realize quartz-embedded horizontal plane Cu inductors, the bottom side is thermo-mechanically bonded on an active wafer using an SU8 photoepoxy semi-hermetic seal. A successful fabrication results in terms of very good adhesion of SU8 bonding, compatibility with fluorine plasma chemistry for MEMS release and very good RF performances (excellent quality factors, higher than 30 at 2 GHz, and self resonant frequency above 6 GHz) was demonstrated