Wafer-Lever Hermetic Package with Through-Wafer Interconnects

This paper reports a new wafer-level hermetic packaging structure with the features of low processing cost and high I/O density by using wet and dry sequentially etched through-wafer vias for the interconnects of a microelectro mechanical systems (MEMS) device. A thin Si wafer cap and wafer-level fabrication processes such as deep reactive ion etching (DRIE) and KOH etching, bottom-up copper filling, and Sn solder bonding were adopted. The hermeticity and bonding strength of the structure are evaluated. Preliminary results show that the hermeticity can meet the requirement of the criterion of MIL-STD 883E, method 1014.9, and the bonding strength is up to 8 MPa.