NARROW FOOTPRINT COPPER SEALING RINGS FOR LOW-TEMPERATURE HERMETIC WAFER-LEVEL PACKAGING

This paper reports a narrow footprint sealing ring design for low-temperature, hermetic, and mechanically stable wafer-level packaging. Copper (Cu) sealing rings that are as narrow as 8 mu m successfully seal the enclosed cavities on the wafers after bonding at a temperature of 250 degrees C. Different sealing structure designs are evaluated and demonstrate excellent hermeticity after 3 months of storage in ambient atmosphere. A leak rate of better than 3.6x10-16 mbarL/s is deduced based on results from residual gas analysis measurements. The sealing yield after wafer bonding is found to be not limited by the Cu sealing ring width but by a maximum acceptable wafer-to-wafer misalignment.