PACKAGING COMPATIBLE WAFER LEVEL CAPPING OF MEMS DEVICES

摘要

The movable part of a 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 pm x 400 pm to 300 mum x 400 um 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.