Thin Film Packaging atmosphere management by solder reflow sealing

Thin Film Packaging (TFP) is a cost effective packaging for MEMS, thanks to the wafer level process, the silicon area saving, and the compatibility with CMOS facilities. One of the most important steps in this process is the sealing of the cap release holes after etching of the sacrificial layer. Standard processes are not well suited for MEMS that require a very controlled and clean atmosphere's cavity or relatively high pressure like RF switches or accelerometers. Such devices have to operate at a certain pressure to fulfill specifications and are sensitive to contaminants that may compromise long term reliability.