Packaging Compatible Wafer Level Capping Of MEMS Devices
Kohl, Paul A.
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This invention discloses and claims a cost-effective, wafer-level package process for microelectromechanical devices (MEMS). Specifically, the movable part of MEMS device is encapsulated and protected while in wafer form so that commodity, lead-frame packaging can be used. An overcoat polymer, such as, epoxycyclohexyl polyhedral oligomeric silsesquioxanes (EPOSS) has been used as a mask material to pattern the sacrificial polymer as well as overcoat the air-cavity. The resulting air-cavities are clean, debris-free, and robust. The cavities have substantial strength to withstand molding pressures during lead-frame packaging of the MEMS devices. A wide range of cavities from 20 μm X 400 μm to 300 μm X 400 μm have been fabricated and shown to be mechanically stable. These could potentially house MEMS devices over a wide range of sizes. The strength of the cavities has been investigated using nano-indentation and modeled using analytical and finite element techniques. Capacitive resonators packaged using this protocol have shown clean sensing electrodes and good functionality.
- Georgia Tech Patents