A low temperature wafer-level hermetic MEMS package using UV curable adhesive

Abstract

In order to lower the packaging cost and resolve the process complexity of MEMS fabrications, a new wafer-level post-process hermetic package using UV curable adhesive bonding is introduced for MEMS applications. The UV curable adhesive is cured through UV light exposure without any additional heating, suitable for packaging the devices with temperature sensitive materials or processes. A Pyrex 7740 glass is micromachined and used as a protection cap substrate with microcavities which is spin-coated with the adhesive, aligned, and bonded with a device substrate to form the package after the UV curing. Finally, electrical contact pads expose and die separation are done simultaneously by dicing. Two different monitoring devices, dew point sensor and capacitive accelerometer are built to evaluate the package strength and hermeticity. After dicing operation, no structure damage or stiction phenomenon is found in the packaged capacitive accelerometer. Furthermore, no moisture condensation is observed in the package with 190 /spl mu/m bonding width after 150 minutes boil water immersion. The acceleration test results indicate the package can survive more than 3 weeks at 25/spl deg/C, 100% RH (relative humidity) working environment.